Huberman Lab - Understand & Improve Memory Using Science-Based Tools

Welcome to the Huberman Lab Podcast,

where we discuss science

and science-based tools for everyday life.

I’m Andrew Huberman,

and I’m a professor of neurobiology and ophthalmology

at Stanford School of Medicine.

Today, we are discussing memory,

in particular, how to improve your memory.

Now, the study of memory is one

that dates back many decades.

And by now, there’s a pretty good understanding

of how memories are formed in the brain,

the different structures involved

and some of the neurochemicals involved.

We will talk about some of that today.

Often overlooked, however,

is that memories are not just about learning.

Memories are also about placing your entire life

into a context.

And that’s because what’s really special about the brain,

and in particular, the human brain,

is its ability to place events

in the context of past events,

the present, and future events,

and sometimes even combinations of the past and present,

or present and future, and so on.

So when we talk about memory,

what we’re really talking about

is how your immediate experiences relate

to previous and future experiences.

Today, I’m going to make clear how that process occurs.

Even if you don’t have a background in biology or psychology,

I promise to put it into language

that anyone can access and understand.

And we are going to talk about the science

that points to specific tools

for enhancing learning and memory.

We’re also going to talk about unlearning and forgetting.

There are, of course, instances

in which we would like to forget things.

And that too is a biological process

for which great tools exist to, for instance,

eliminate or at least reduce the emotional load

of our previous experience that you really did not like,

or that perhaps even was traumatic to you.

So today, you’re going to learn

about the systems in the brain and body

that establish memories.

You’re going to learn why certain memories

are easier to form than others.

And I’m going to talk about specific tools

that are grounded in not just one,

not just a dozen,

but well over a hundred studies in animals and humans

that point to specific protocols

that you can use in order to stamp down

learning of particular things more easily.

And you can also leverage that same knowledge

to better forget or unload the emotional weight

of experiences that you did not like.

We are also going to discuss topics like deja vu

and photographic memory.

And for those of you that do not have a photographic memory,

and I should point out

that I do not have a photographic memory either.

Well, you will learn how to use your visual system

in order to better learn visual and auditory information.

There are protocols to do this

grounded in excellent peer-reviewed research.

So while you may not have a true photographic memory,

by the end of the episode, you will have tools in hand,

or I should say tools in mind or in eyes and mind

to be able to encode and remember specific events

better than you would otherwise.

Before we begin, I’d like to emphasize

that this podcast is separate from my teaching

and research roles at Stanford.

It is however, part of my desire and effort

to bring zero cost to consumer information

about science and science-related tools

to the general public.

In keeping with that theme,

I’d like to thank the sponsors of today’s podcast.

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Okay, let’s talk about memory,

and let’s talk about how to get better

at remembering things.

Now, in order to address both of those things,

we need to do a little bit of brain science 101 review,

and I promise this will only take two minutes,

and I promise that even if you don’t have a background

in biology, it will make sense.

We are constantly being bombarded with physical stimuli,

patterns of touch on our skin, light to our eyes,

light to our skin for that matter,

smells, tastes, and sound waves.

In fact, if you can hear me saying this right now,

well, that’s the consequence of sound waves

arriving into your ears through headphones, a computer,

or some other speaker device.

Each one of, and all of those sensory stimuli

are converted into electricity and chemical signals

by your so-called nervous system,

your brain, your spinal cord,

and all their connections with the organs of the body,

and all the connections of your organs of the body

back to your brain and spinal cord.

One of the primary jobs of your nervous system, in fact,

is to convert physical events in the world

that are non-negotiable, right?

Photons of light are photons of light.

Sound waves are sound waves.

There’s no changing that,

but your nervous system does change that.

It converts those things into electrical signals

and chemical signals,

which are the language of your nervous system.

Now, just because you’re being bombarded

with all the sensory information,

and it’s being converted into a language that neurons

and the rest of your nervous system can understand

does not mean that you are aware of it all.

In fact, you are only going to perceive a small amount

of that sensory information.

For instance, if you can hear me speaking right now,

you are perceiving my voice,

but you are also most likely neglecting the feeling

of the contact of your skin with whichever surface

you happen to be sitting or standing on.

So it is only by perceiving a subset,

a small fraction of the sensory events in our environment,

that we can make sense of the world around us.

Otherwise we would just be overwhelmed

with all the things that are happening

in any one given moment.

Now, memory is simply a bias in which perceptions

will be replayed again in the future.

Anytime you experience something,

that is the consequence of specific chains of neurons

that we call neural circuits being activated.

And memory is simply a bias in the likelihood

that that specific chain of neurons will be activated again.

So for instance, if you can remember your name,

and I certainly hope that you can,

well, that means that there are specific chains

of neurons in your brain that represent your name.

And when those neurons connect with one another

and communicate electrically with one another

in a particular sequence, you remember your name.

Were that particular chain of neurons to be disrupted,

you would not be able to remember your name.

Now, this might seem immensely simple,

but it raises this really interesting question,

which we talked about before,

which is why do we remember certain things and not others?

Because according to what I’ve just said,

as you go through life,

you’re experiencing things all the time.

You’re constantly being bombarded with sensory stimuli.

Some of those sensory stimuli you perceive,

and only some of those perceptions

get stamped down as memories.

Today, I’m going to teach you how certain things

get stamped down as memories.

And I’m going to teach you how to leverage that process

in order to remember the information

that you want far better.

Now, even though I’ve told you that a memory

is simply a bias in the likelihood

that a particular chain of neurons will be activated

in a particular sequence again and again,

it doesn’t operate on its own.

In fact, most of what we remember

takes place in a context of other events.

So for instance, you can most likely remember your name,

and yet you’re probably not thinking about

when it was that you first learned your name.

This generally happens

when we are very, very young children.

And yet, I’m guessing you could probably remember

a time when someone mispronounced your name

or made fun of your name,

or as the case was for me,

I got to the third grade and there were two Andrews.

And sadly for me, I lost the coin flip

that allowed me to keep Andrew.

And from about third grade until about 12th grade,

people called me Andy, which I really did not prefer.

So if you call me Andy in the comments,

I’ll delete your comment.

Just kidding, doesn’t bother me that much.

But eventually I reclaimed Andrew as my name.

Well, it was mine to begin with and throughout,

but I started going by Andrew again.

Why do I say this?

Well, there’s a whole context to my name for me.

And there may or may not be a whole context

to your name for you,

but presumably if you asked your parents

why they named you your given name,

you’ll get a context, et cetera.

That context reflects the activation

of other neural circuits that are also related

to other events in your life, not just your name,

but probably your siblings’ names

and who your parents are and on and on and on.

And so the way memory works is that each individual thing

that we remember or that we want to remember

is linked to something by either a close,

a medium, or a very distant association.

This turns out to be immensely important.

I know many of you will read or will encounter programs

that are designed to help you enhance your memory.

You know, you have these phenomes that can remember

50 names in a room full of people,

or they can remember a bunch of names of novel objects

or maybe even in different languages.

And oftentimes that’s done by association.

So people will come up with little mental tricks

to either link the sound of a word

or the meaning of a word in some way

that’s meaningful for them and will enhance their memory.

That can be done and is impressive when we see it.

And for those of you who can do that, congratulations.

Most of us can’t do that,

or at least it requires a lot of effort and training.

However, there are things that we can do

that leverage the natural biology of our nervous system

to enhance learning and memory of particular perceptions

and particular information.

Let’s first just talk about the most basic ways

that we learn and remember things

and how to improve learning and memory.

And the most basic one is repetition.

Now, the study of memory and the role of repetition

actually dates back to the late 1800s, early 1900s,

when Ebbinghaus developed

the first so-called learning curves.

Now, learning curves are simply what results

when you quantify how many repetitions of something

are required in order to remember something.

In fact, it’s been said that Ebbinghaus liberated

the understanding of learning from the philosophers

by generating these learning curves.

What do we mean by that?

Well, before Ebbinghaus came along,

learning and memory were thought to be philosophical ideas.

Ebbinghaus came along and said,

well, let’s actually take some measurements.

Let’s measure how well I can remember a sequence of words

or a sequence of numbers if I just repeat them.

So what Ebbinghaus did is he would take a sequence of

numbers or words on a page and he would read them.

And then he would take a separate sheet of paper

and we have to presume he didn’t cheat.

And he would write down as many of them as he could.

And he would try and keep them in the same sequence.

Then he would compare to the original list

and he would see how many errors he made.

And you do this over and over and over again.

And as you would expect early in the training

and the learning, it took a lot more repetitions

to get the sequence correct.

And over time it took fewer sequences.

And he referred to that difference in the initial number

of repetitions that he had to perform

versus the later number of repetitions

that he had to perform as a so-called savings.

So he literally thought of the brain as having to generate

a kind of a currency of effort.

And he talked about savings as the reduction

in the amount of effort that he had to put forward

in order to learn information.

And what he got was a learning curve.

And you can imagine what that learning curve looked like.

It was at a very sharp peak at the beginning

that dropped off over time.

And of course he remembered

all this meaningless information.

But even though the information might’ve been meaningless,

the experiment itself and what Ebbinghaus demonstrated

was immensely meaningful.

Because what it said was that with repetition,

we can activate particular sequences of neurons

and that repeated activation lays down

what we call a memory.

And that might all seem like a big duh,

but prior to Ebbinghaus, none of that was known.

Now I should also say Ebbinghaus,

because of when he was alive,

was not aware of these things that we call neural circuits.

It was in 1906 that Golgi and Cajal got the Nobel prize

for actually showing that neurons are independent cells

connected by synapses,

these little gaps between them where they communicate.

So he may have been aware of that,

but the whole notion of neural circuits

hadn’t really come about.

Nevertheless, what the Ebbinghaus learning curves

really established was that sheer repetition,

just repeating things over and over and over again

is sufficient to learn.

Something that no doubt had been observed before,

but it had never been formally quantified.

Now, if we look at that result,

there’s something really important

that lies a little bit cryptic,

that’s not so obvious to most people,

which is the information that he was trying to learn

wasn’t any more interesting the second time

than it was the first,

probably was even less interesting

and less and less interesting with each repetition.

And yet it was sheer repetition

that allowed him to remember.

Now, sometime later in the early to mid 1920s,

a psychologist in Canada named Donald Hebb

came up with what was called Hebb’s postulate.

And Hebb’s postulate, broadly speaking,

is this idea that if a sequence of neurons is active

at the same time, or at roughly the same time,

that that would lead to a strengthening of the connections

between those neurons.

And many, many decades of experimentation later,

we now know that postulate to be true.

Neurons themselves are not smart,

they don’t have knowledge.

So every memory is the consequence,

as I told you before,

of the repeated activation of a particular chain of neurons.

And what Ebbinghaus showed through repetition

and what Donald Hebb proposed

and was eventually verified through experimentation

on animals and humans,

was that if you encourage the co-activation of neurons,

meaning have neurons fire at roughly the same time,

they will strengthen their connections.

It leads to a bias in the probability

that those neurons will be active again.

Now, this is vitally important

because nowadays we hear a lot

about how memories are the consequence

of new neurons added in the brain,

or that every time you learn something,

a new connection in your brain forms.

Well, sorry to break it to you,

but that’s simply not the case.

Most of the time, and I want to emphasize most,

not all, but most of the time when we learn something,

it’s because existing neurons, not new neurons,

but existing neurons strengthen their connection

through co-activation over and over and over

through repetition, or, and this is a very important or,

or through very strong activation once and only once.

In fact, there’s something called one trial learning

whereby we experience something

and we will remember that thing forever.

This is often most associated with negative events,

and I’ll explain why in a few minutes,

but it can also be associated with positive events,

like the first time you saw your romantic partner

or something that happened with that romantic partner,

or the first time that you saw your child,

or any other positive event,

as well as any other extremely negative event.

So again, both repetition and,

I guess we could label it intensity,

but what we really mean when we say intensity

is strong activation of neurons can lay down these traces,

these circuits that are far more likely to be active again,

than had there not been repetition

or not some strong activation of those circuits.

So with that in mind,

let’s return to the original contrarian question

that I raised before,

which is why do we remember anything?

Every day you wake up,

your neurons in your brain and body are active,

different neural circuits are active,

and yet you only remember a small fraction

of the things that happen each day,

and yet you retain a lot of information

from previous days and the days before those and so on.

It is only with a lot of repetition

or with extremely strong activation of a given neural circuit

that we will create new memories.

And so in a few minutes,

I’ll explain how to get extremely strong activation

of particular neural circuits.

Repetition is pretty obvious, repetition is repetition,

but in a few minutes,

I’ll illustrate a whole set of experiments

and a whole set of tools that point to how you can get

extra strong activation of a given neural circuit

as it relates to learning

so that you will remember that information,

perhaps not just with one trial of learning,

but certainly with far fewer repetitions

than would be required otherwise.

Before we go any further,

I want to preface the discussion by saying

that there are a lot of different kinds of memory.

In fact, were you to take a voyage into the neuroscience

and or psychology of memory,

you would find an immense number of different terms

to describe the immense number of different types of memory

that researchers focus on.

But for sake of today’s discussion,

really just want to focus on short-term memory,

medium-term memory, and long-term memory.

And while there’s still debate,

as is always the case with scientists, frankly,

about the exact divisions between short-term,

medium, and long-term memory,

we can broadly define short-term memory

and long-term memory,

and we can describe a couple of different types of those

that I think you can relate to in your everyday life.

The most common form of short-term memory

that we’re going to focus on is called working memory.

Working memory is your ability to keep a chain of numbers

in mind for some period of time,

but the expectation really isn’t

that you would remember those numbers the next day,

and certainly not the next week.

So a good example would be a phone number.

If I were to tell you a phone number, 493-2938,

well, you could probably remember it, 493-2938.

But if I came back tomorrow and asked you

to repeat that chain of numbers, most likely you would not,

unless, of course, we used a particular tool

to stamp down that memory into your mind

and commit it to long-term memory.

Now, of course, in this day and age,

most people have phone numbers programmed into their phone.

They don’t really have to remember the exact numbers.

It’s usually done by contact identity and so forth.

So a different example

that some of you are probably more familiar with

would be those security codes.

So you try and log on to an app or a website,

and it asks you for a security code

that’s been sent to your text messages,

and then you can either plug that in directly in some cases,

or you have to remember that short sequence of anywhere,

usually from six to seven, sometimes eight numbers.

Your ability to do that, to switch back and forth

between webpages or apps and plug in that number

by remembering the sequence and plugging it in

by texting or keying it in on your keyboard,

that’s a really good example of working memory.

Long-term memory of the sort

that we’re going to be talking a lot about today

is your ability to commit certain patterns of information,

either cognitive information or motor information, right?

The ability to move your limbs in a particular sequence

over long periods of time,

such that you could remember it a day or a week or a month,

or maybe even a year or several years later.

So we’ve got short-term memory and long-term memory,

and we’ve got this working memory,

which is kind of keeping something online,

but then discarding it, okay?

Not online on a computer, but online within your brain.

There are also two major categories of memory

that I’d like you to know about.

One is explicit memory.

So this is not necessarily explicit of the sort

that you’re used to thinking about,

but rather the fact that you can declare you know something.

So you have an explicit memory of your name.

Presumably you have an explicit memory

of the house or the apartment that you grew up in.

You know something and you know you know it,

and you can declare it.

So I can ask you,

what was the color of the first car that you owned?

Or what is the color of your romantic partner’s hair?

These sorts of things.

That’s an explicit declarative memory,

but you also have explicit procedural memories.

Now, procedural memories, as the name suggests,

involve action sequences.

The simplest one, it’s almost ridiculously simple,

is walking.

If I say, how is it that you walk

from one room to the other?

You’d probably say, well, I go that direction,

then I turn left.

I say, no, no, no, no.

How is it exactly that you do it?

And say, well, I move my left foot,

then my right foot, then my left foot.

And you could describe that.

So it’s an explicit procedural memory.

So much so that if you were going to teach

a young toddler how to walk,

you would probably say, okay, good, good, try.

Okay, and you know,

probably that’s going to be pre-language for the toddler,

but you’re going to encourage them to move one leg,

then the other,

and you’re going to encourage and reward them

for moving one leg, then the other,

because you have an explicit procedural memory

of how to walk.

Okay, almost ridiculously simple.

Maybe even truly ridiculously simple,

but nonetheless,

when you think about it in the context of neural circuits

and neural firing, pretty amazing.

Even more amazing is the fact that all explicit memories,

both declarative and procedural explicit memories,

can be moved from explicit to implicit.

What do I mean by that?

Well, in the example of walking,

you might’ve chuckled a little bit

or kind of shook your head

and said, that’s a ridiculous thing to ask.

How do I walk from one room to the next?

I just walk, I just do it.

Ah, well, what is just do it?

What it is, is that you have an implicit understanding,

meaning your nervous system knows how to walk

without you actually having to think about

what you know about how to walk.

You just get up out of your chair

or you get up out of bed and you walk.

In the brain, you have a structure.

In fact, you have one on each side of your brain.

It’s called the hippocampus.

The hippocampus literally means seahorse.

Anatomists like to name brain structures

after things that they think those brain structures resemble.

When I look at the hippocampus,

frankly, it doesn’t look like a seahorse,

which either reflects my lack of understanding

of what a seahorse really looks like, a visual deficit,

or I think it’s fair to say that those anatomists

were using a little bit of creative elaboration

when thinking about what the hippocampus looks like.

Nonetheless, it is a curved structure.

It has many layers.

It’s been described by my colleague, Robert Sapolsky,

and by others as looking more like a jelly roll

or a cinnamon roll is what it looks like to me.

And if you were to take one cinnamon roll,

chop it down the middle.

So now you’ve got two half cinnamon rolls.

And rather than put them back together

in the configuration they were before,

you just slide one down so that you’ve got

essentially two Cs, two C-shaped halves of the cinnamon roll

and you push them together, right?

Slightly offset from one another,

well, that’s what the hippocampus looks like to me.

And I think that’s a far better description

of its actual physical structure.

But I guess if you were to use that physical structure

as the name, well, then you’d have to open up

a brain atlas and it would be called

two half C cinnamon rolls stuffed halfway together.

So that’s not very good.

So I guess seahorse will work.

Hippocampus is the name of this structure

and it is the site in your brain.

And again, you have one on each side of your brain

in which explicit declarative memories are formed.

It is not where those memories are stored and maintained.

It is where they are established in the first place.

In contrast, implicit memories, right?

These subconscious memories are formed and stored

elsewhere in the brain,

mainly by areas like the cerebellum,

but also the neocortex,

the kind of outer shell of your brain.

The cerebellum is, it literally means mini brain.

And it does in fact look like a mini brain

and is in the back of the brain.

And the neocortex is the outer part of the brain

that covers all the other stuff.

So the hippocampus is vitally important for establishing

these new declarative memories of what you know

and what you know how to do.

Now, in order to really understand the role

of the hippocampus in memory,

in particular explicit declarative

and explicit procedural memory,

and to really understand how that’s distinct

from implicit declarative and implicit procedural memories,

we have to look to a clinical case.

And the clinical case that I’m referring to is a patient

who went by the name HM.

Patients go by their initials in order to maintain

confidentiality of their real identity.

HM had what’s called intractable epilepsy.

So he would have these really dramatic

so-called grand mal seizures or drop seizures.

For those of you that know somebody with epilepsy

or that have epilepsy, you might be familiar with this.

You can have petite mal seizures, which are minor seizures.

You can have tonic-clonic seizures,

which are sometimes not even detectable.

You can have absent seizures where people will just stop.

It’s almost as if their brain kind of goes on pause

and they’ll just stop there.

It was reported actually that Einstein had absent seizures,

although I don’t know that that’s ever really

been confirmed neurologically.

Grand mal seizures are extremely severe,

and that’s what HM had.

So he could just be going about his day

and maybe even cooking or doing something, driving,

operating any kind of machinery.

And then all of a sudden he would just have a drop seizure.

So he would just physically drop

and go into a grand mal seizure.

So convulsing of the whole body,

loss of consciousness, et cetera.

Or he would feel it coming on.

Oftentimes people with epilepsy can feel

the epilepsy seizure coming on kind of like a wave

from the back of the brain.

And sometimes they can get to a safe circumstance,

but not always.

And so the frequency and the intensity of his seizures

were so robust that the neurosurgeons and neurologists

decided that they need to locate the origin,

what they call the foci of those seizures,

and remove that brain tissue.

Because the way seizures work is they spread out

from that focus or that foci of brain tissue.

And unfortunately for HM,

the focus of his seizures was the hippocampus.

So after a lot of deliberation,

a neurosurgeon, in fact,

one of the most famous neurosurgeons in the world

at that time made what are called electrolytic lesions,

actually burned out the hippocampus in the brain of HM.

And as a consequence, he lost all explicit memory.

Now, the consequence of this was that he couldn’t exist

in normal everyday life like most people.

So he had to live mostly, not entirely,

but mostly in a kind of hospital setting.

And I’ve talked to several people who have,

I should say, who met HM directly

because he’s no longer alive,

but an interaction with him might look like the following.

He would walk up to you just fine.

You wouldn’t know that he had any kind of brain damage.

He could walk fine.

He could speak fine.

And he’d say, hi, I’m Andrew.

And he’d say, hi, I’m whatever his name happened to be.

He wouldn’t say HM, but he’d probably say his real name.

And then perhaps someone new would walk into the room.

He might turn around, look at that person

as any of us might do, then turn around back to me

and say, hi, what’s your name?

And if I were to say, well, I just told you my name

and you just told me your name, do you remember that?

He’d say, I’m sorry, I don’t remember any of that.

What’s your name?

So you had to go through this over and over again.

So a complete lack of explicit declarative memory.

Now he did have some memory for previous events in his life

that dated way back, okay?

Again, hinting at the idea that memories

are not necessarily stored in the hippocampus.

They’re just formed in the hippocampus.

So once they’ve moved out of the hippocampus

to other brain areas, he could still keep those memories.

They’re in a different database, if you will.

They’re in a different pattern of firing

of other neural circuits, but he couldn’t form new memories.

Now there’s some very important and interesting twists

on what HM could and could not do

in terms of learning and memory

that teach us a lot about the brain.

In fact, I think most neuroscientists would agree

that this unfortunate case of HM’s epilepsy

and the subsequent neurosurgery that he had

taught us much of what we know, or at least think about

in terms of human learning and memory.

For instance, as I mentioned before,

he still had implicit knowledge.

He knew how to walk.

He knew how to do certain things like make a cup of coffee.

He knew the names of people that he had met much earlier

in his life and so on.

And yet he couldn’t form new memories.

Now, in violation to that last statement,

there were some elements of HM’s emotionality

that suggests that there was some sort of residual capacity

to learn new information,

but it wasn’t what we normally think of

as explicit declarative or procedural memory.

For instance, it’s been reported or it’s been said,

I should say, because I don’t know that the studies

were ever done with intense physiological measurements,

that if you were to tell HM a joke

and he thought it was funny, he would laugh really hard.

So he liked jokes.

So you’d tell him, you’d say,

HM, I want to tell you a joke.

You tell him a joke and he’d laugh really hard.

Then you could leave the room, come back

and tell him the same joke again.

Now, keep in mind, he did not remember

that you told him the joke previously.

And the second time he would laugh a little bit less.

And then you’d leave the room, come back again,

say, hi, I’m Andrew.

And he’d say, oh, nice to meet you.

Because as you know, as you recall,

because you can recall things,

but he couldn’t recall things.

He didn’t know that he just met you

or at least he couldn’t remember it.

You tell him the joke a third time or a fourth time.

And with each subsequent telling of the joke,

he found it a little less funny,

just as, keep this in mind, folks,

if you tell a joke and you get a big laugh,

don’t tell it again, at least not immediately,

not to the same person or the same crowd,

because the second time it’s a little less funny.

And the third time it’s a little less funny.

And that actually has to do with a whole element

of dopamine and its relationship to surprise.

And that’s the topic of a future podcast

where we talk all about humor and novelty in the brain.

But the point being that certain forms of memory

seem to exist in a kind of phantom-like way

within HM’s brain.

What do I mean by that?

Well, this underscores the fact

that he had an implicit memory

of having heard the joke before.

And it suggests that humor,

or at least what we find funny,

is somehow more related to procedures

similar to walking or a motor ability

than it is to this precise content of that joke.

All right, that’s a little bit of an abstract concept,

but the point is that HM lacked

explicit declarative memory.

He couldn’t tell you what he had just heard.

He could not learn new information.

And he couldn’t tell you how to do something

unless he had learned how to do that something

many years prior.

Now, there’ve been a lot of other patients besides HM

that have had brain lesions due to epilepsy,

or I should say due to surgeries to treat epilepsy,

due to strokes, due to sadly gunshot wounds

and other forms of what we call infarcts,

infarct, I-N-F-A-R-C-T, infarct,

is the word we use to describe damage

to a particular brain region.

And many different patients

with many different patterns of infarct

have taught us a lot about how memory

and other aspects of the brain work.

HM really teaches us that what we know

and what we are able to do

is the consequence of things that we are aware of

and learnings that have been passed off

into subconscious knowledge that our body knows,

our brain knows,

but we don’t know exactly how we know that thing.

And I tell you the story about HM’s ability

to understand a joke,

but that with repeated telling of a joke,

it has less and less and less of an impact

in creating a sense of laughter, of humor in HM,

not as just an anecdote to flesh out his story,

but because emotion itself

turns out to be the way in which we can enhance memories,

even if those are memories for things that are not funny,

are not intensely sad, are not immensely happy,

or don’t evoke a really strong emotional response

or even any emotional response.

And the reason for that is that emotions,

just like perception, just like sensation,

are the consequence of particular neurochemicals

being present in our brain and body.

And as I’m going to tell you next,

there are particular neurochemicals that you can leverage

in order to learn specific information faster

and to remember it for a much longer period of time,

maybe even forever.

And you can do that by leveraging the relationship

in your nervous system between your brain and your body

and your body back to your brain.

So let’s talk about tools for enhancing memory.

Now there’s one tool that is absolutely clear, works.

And it’s always worked, it works now,

and it will work forever.

And that’s repetition.

The more often that you perform something

or that you recite something,

the more likely you are to remember it in the future.

And while that might seem obvious,

it’s worth thinking about what’s happening

when you repeat something.

But when I say what’s happening,

I mean, at the neural level.

What’s happening is that you’re encouraging

the firing of particular chains of neurons

that reside in a particular circuit, right?

So a particular sequence of neurons playing neuron A, B, C,

D played in that particular sequence

over and over and over again.

And with more repetitions,

you get more strengthening of those nerve connections.

Now, repetition works,

but the problem for most people

is that they either don’t have the patience,

they don’t have the time,

and sometimes they literally don’t have the time

because they’ve got a deadline

on something that they’re trying to remember and learn,

or they simply would like to be able

to remember things better in general,

remember them more quickly.

This process of accelerating repetition-based learning

so that your learning curve doesn’t go

from having to perform something 1,000 times,

and then gradually over time,

it’s 1,750 times a day, 500 times a day,

300 times a day, and down to no repetitions, right?

You can just perform that thing

the first time and every time.

Well, there is a way to shift that curve

so that you can essentially establish stronger connections

between the neurons that are involved

in generating that memory or behavior more quickly.

How do you do that?

Well, in order to answer that,

we have to look at the beautiful work

of James McGaw and Larry Cahill.

James McGaw and Larry Cahill did a number of experiments

over several decades, really,

based on a lot of animal literature,

but mainly focused on humans

that really established what’s required

to get better at remembering things

and to do so very quickly.

I want to talk about one experiment that they did

that was particularly important.

And we will provide a link to this paper.

It’s some years old now, but the results still hold up.

In fact, the results establish an entire field

of memory in neuroscience and psychology.

What they did is they had human subjects

come into the laboratory and to read a short paragraph

of about 12 sentences.

And the key thing is that some subjects read a paragraph

that was pretty mundane.

The content, the information within the paragraph

was all related to the content of the previous sentence.

So it was a cogent paragraph, right?

It just wasn’t meaningless scramble of words,

but it described a kind of mundane set of circumstances.

Maybe it would be a story about someone

who walked into a room, sat down at a desk,

wrote for a little bit, then got up and had lunch.

You know, just kind of mundane information,

not very interesting.

Another group of subjects read also a 12-sentence paragraph,

but that paragraph included a subset of sentences

that had a lot of emotionally intense language

or that had language that could evoke

an emotionally intense response in the person reading it.

So it might’ve talked about a car accident

or a very intense surgery,

but it also could be positive stuff.

Things like a birthday party

or a celebration of some other kind or a big sports win.

So in other words, you have two conditions of this study.

People either read a boring paragraph

or they read a really emotionally laden paragraph.

And again, the emotions could either be positive

or negative emotions.

Subjects left the laboratory and sometime later,

they were called back to the laboratory.

And I should say at no point in the experiment

did they know they were part of a memory experiment, okay?

They don’t know why they’re reading this paragraph.

They came in either for class credit or to get paid.

It’s typically how these things are done

on college campuses or elsewhere.

They come back into the lab and they would get a pop quiz.

They would be asked to recall the content

of the paragraph that they had read previously.

Now, as is probably expected, perhaps even obvious to you,

the subjects that read the emotionally intense paragraph

remembered far more of the content of that paragraph

and were far more accurate

in their remembering of that information.

Now, that particular finding wasn’t very novel.

Many people had previously described

how emotionally intense events are better remembered

than non-emotionally intense events.

In fact, way back in the 1600s, Francis Bacon,

who’s largely credited

with developing the scientific method,

said, quote, memory is assisted by anything

that makes an impression on a powerful passion,

inspiring fear, for example, or wonder, shame, or joy.

Francis Bacon said that in 1620.

So Jim McGaugh and Larry Cahill

were certainly not the first to demonstrate

or to conceive of the idea

that emotionally laden experiences

are more easily remembered than other experiences.

However, what they did next was immensely important

for our understanding of memory

and for our building of tools to enhance learning and memory.

What they did was they evaluated the capacity for stress

and for particular neurochemicals associated with stress

to improve our ability to learn information,

not just information that is emotional,

but information of all kinds.

So I’m going to describe some experiments

done in animal models just very briefly,

and then experiments done on human subjects,

because McGaugh worked mainly on animals,

also human subjects,

Larry Cahill almost exclusively on human subjects.

If you take a rat or a mouse and put it in an arena

where at one location, the animal receives

an electrical shock, and then you come back the next day,

you remove the shock evoking device

and you let the animal move around that arena,

that animal will quite understandably avoid the location

where it was shocked, so-called conditioned place aversion.

That effect of avoiding that particular location

occurs in one trial.

That’s a good example of one trial learning.

So somehow the animal knows

that it was shocked at that location.

It remembers that it is a hippocampal dependent learning.

So animals that lack a hippocampus

or who have their hippocampus pharmacologically

or otherwise incapacitated

will not learn that new bit of information,

but for animals that do,

they remember it after the first time and every time,

unless you are to block the release of certain chemicals

in the brain and body,

and the chemicals I’m referring to

are epinephrine, adrenaline,

and to some extent, the corticosterones,

things like cortisol.

Now we know that the effect of getting one trial learning

somehow involves epinephrine,

at least in this particular experimental scenario,

because if researchers do the exact same experiment,

and they have done the exact same experiment,

but they introduce a pharmacological blocker of epinephrine

so that epinephrine is released in response to the shock,

but it cannot actually bind to its receptors

and have all of its biological effects,

well, then the animal is perfectly happy

to tread back into the area where it received the shock.

It’s almost as if it didn’t know

or we have to assume that it didn’t remember

that it received the shock at that location.

So it all seems pretty obvious when you hear it,

something bad happens in a location,

you don’t go back to that location.

So that’s conditioned place avoidance,

but it turns out that the opposite is also true,

meaning for something called conditioned place preference,

you can take an animal, put it into an arena,

feed it or reward it somehow at one location in that arena.

So you can give a hungry rat or mouse food

at one particular location,

take the animal out, come back the next day,

no food is introduced,

but it will go back to the location

where it received the food,

or you can do any variant of this.

You can make the arena a little bit chilly

and provide warmth at that location,

or you can take a male animal,

it turns out male rats and mice will mate at any point

or a female animal that’s at the particular

so-called receptive phase of her mating cycle

and give them an opportunity to mate at a given location,

they’ll go back to that location and wait and wait.

This is perhaps why people go back to the same bar

or the bar seat at the bar or the same restaurant

and wait because of the one time they,

things worked out for them, whatever the context was.

Conditioned place preference.

Conditioned place preference

as with conditioned place avoidance

depends on the release of adrenaline, right?

It’s not just about stress,

it’s about a heightened emotional state

in the brain and body.

Okay, this is really important.

It’s not just about stress.

You can get one trial learning for positive events,

conditioned place preference,

and you can get one trial learning for negative events.

Here, I say positive, negative,

I’m putting what’s called valence on,

I’m making a value judgment about whether or not

the animal liked it or didn’t like it,

and we have to presume what the animal liked or didn’t like

and how it felt,

but this turns out all to be true for humans as well.

We know that because McGaugh and Cahill did experiments

where they gave people a boring paragraph to read

and only a boring paragraph to read,

but one group of subjects was asked to read the paragraph

and then to place their arm into very, very cold water.

In fact, it was ice water.

We know that placing one’s arm into ice water,

especially if it’s up to the shoulder or near to it,

evokes the release of adrenaline in the body.

It’s not an enormous release,

but it’s a significant increase.

And yes, they measured adrenaline release.

In some cases, they also measured

for things like cortisol, et cetera.

And what they found is that if one evokes the release

of adrenaline through this arm into ice water approach,

the information that they read previously,

just a few minutes before, was remembered.

It was retained as well as emotionally intense information.

But keep in mind that information that they read

was not interesting at all,

or at least it wasn’t emotionally laden.

This had to be the effect of adrenaline released

into the brain and body,

because if they blocked the release

or the function of adrenaline in the brain and or body,

they could block this effect.

Now, the biology of epinephrine and cortisol

are a little bit complex,

but there’s some nuance there that’s actually interesting

and important to us.

First of all, adrenaline is released in the body

and in the brain.

It’s released in the body from the adrenals.

Remember, epinephrine and adrenaline are the same thing.

Cortisol is also released from the adrenal glands,

these two little glands that ride atop our kidneys,

but it can’t cross into the brain.

It only has what we call peripheral effects,

quickening of the heart rate, right?

Changes the patterns of blood flow,

changes our patterns of breathing,

in general makes our breathing more shallow and faster,

in general makes our heartbeat more quickly, et cetera.

Within our brain, we have a little brain area

called locus coeruleus, which is in the back of the brain,

which has the opportunity to sprinkler the rest of the brain

with the neuromodulator epinephrine, adrenaline,

as well as norepinephrine, a related neuromodulator,

and to essentially wake up or create a state of alertness

throughout the brain.

So it’s a very general effect.

The reason we have two sites of release

is because these neurochemicals

do not cross the blood-brain barrier.

And so waking up the body with adrenaline

and waking up the brain are two separate

so-called parallel phenomena.

Cortisol can cross the blood-brain barrier

because it’s lipophilic,

meaning it can move through fatty tissue.

And we’ll get into the biology of that in another episode,

but cortisol in general is released

and has much longer-term effects.

And as I’ve just told you,

can permeate throughout the brain and body.

Adrenaline has more local effects

or at least is segregated between the brain and the body.

This will turn out to be important later.

The important thing to keep in mind

is that it is the emotionality evoked by an experience,

or to be more precise,

it is the emotional state that you’re in

after you experience something

that dictates whether or not

you will learn it quickly or not.

This is absolutely important

in terms of thinking about tools to improve your memory.

And no, I am not going to suggest

that every time you want to learn something,

you plunge your arm into ice water.

Why won’t I suggest that?

Well, it will induce the release of adrenaline,

but there are better ways to get that adrenaline release.

Before I explain exactly what those tools are,

I want to tamp down the biology of how all this works,

because in that understanding,

you will have access to the best possible tools

to improve your memory.

First of all, McGaugh and Cahill

were excellent experimentalists.

They did not just establish

that you could quicken the formation of a memory

by accessing material that was very emotionally laden

or creating an emotional high adrenaline state

after interacting with some thing,

some word, some person, some information.

They also tested whether or not

that whole effect could be blocked

by blocking the emotional state

or by blocking adrenaline.

So what they did is they had people read paragraphs

that either had a lot of emotional content,

or they had people read paragraphs that were pretty boring,

but then had them put their arm into ice water.

And I should say they did other experiments too

to increase adrenaline.

There were even some shock experiments

that were done by other groups.

Any number of things to evoke the release of adrenaline,

even people taking drugs that increase adrenaline.

But then they also did what are called blocking experiments.

They did experiments where they had people

get into a highly emotional state

from reading highly emotional material,

or they got people to get into

a highly emotional neurochemical state

by reading boring material

and then taking a drug to increase adrenaline

or ice bath or a shock.

And then they also administered a drug

called a beta blocker

to block the effect of adrenaline

and related chemicals in the brain and body.

And what they found is that even if people

were exposed to something really emotional

or had a lot of adrenaline in their system

because they received a drug

to increase the amount of adrenaline,

two manipulations that normally would increase memory,

keep that in mind.

If they gave them a beta blocker,

which reduced the response to that adrenaline, right?

So no quickening of the heart rate,

no quickening of the breathing,

no increase in the activity of locus coeruleus

and these kind of wake up signals to the rest of the brain.

Well, then the material wasn’t remembered better at all.

What this tells us is that, yes, Francis Bacon was right.

McGaw and Cahill were right.

Hundreds, if not thousands of philosophers and psychologists

and neuroscientists were right

in stating and in thinking that high emotional states

help you learn things.

But what McGaw and Cahill really showed

and what’s most important to know

is that it is the presence of high adrenaline,

high amounts of norepinephrine and epinephrine

and perhaps cortisol as well, as you’ll soon see,

that allows a memory to be stamped down quickly.

It is not the emotion.

It is the neurochemical state that you go into

as a consequence of the emotion.

And it’s very important to understand

that while those two things are related,

they are not one in the same thing.

Because what that means is that were you to evoke

the release of epinephrine, norepinephrine and cortisol,

or even just one or two of those chemicals,

after experiencing something,

you are stamping down the experience

that you just previously had.

Now, this is fundamentally important

and far and away different than the idea

that we remember things because they’re important to us

or because they evoke emotion.

That’s true, but the real reason,

the neurochemical reason, the mechanism behind all that

is these neurochemicals have the ability

to strengthen neural connections

by making them active just once.

There’s something truly magic

about that neurochemical cocktail

that removes the need for repetition.

Okay, so let’s apply this knowledge.

Let’s establish a scientifically grounded set of tools,

meaning tools that take into account

the identity of the neurochemicals

that are important for enhancing learning

and the timing of the release of those chemicals

in order to enhance learning.

When I first learned about the results of McGaugh and Cahill

I was just blown away.

I was also pretty upset, but not with them.

I was upset with myself because I realized

that the way that I’d been approaching learning and memory

was not optimal.

In fact, it was probably in the opposite direction

to the enhanced protocol for learning and memory

that I’m going to teach you today.

My typical mode of trying to learn something

while I was in college or while I was in graduate school

or as a junior professor or even a tenured professor

was to sit down to whatever it is I was going to try

and learn, perhaps even memorize,

or if it was a physical skill,

move to whatever environment I was going to learn

that physical skill in.

And prior to that, to make sure that I was hydrated,

because that’s important to me

and certainly can contribute to your brain’s ability

to function and your body’s ability to function

and general patterns of alertness, but also to caffeinate.

I would have a nice strong cup of coffee or espresso.

I would have a nice strong cup of yerba mate.

And I still drink coffee or yerba mate very regularly.

I drink them in moderation, I think, certainly for me,

but typically I would drink those things

before I would engage in any kind of attempt

to learn or memorize or to acquire a new skill.

Now, caffeine in the form of coffee or yerba mate

or any other form of caffeine

does create a sense of alertness in our brain and body.

And it does that through two major mechanisms.

The first mechanism is by blocking the effects of adenosine.

Adenosine is a molecule that builds up in the brain and body

the longer that we are awake.

And it’s largely what’s responsible

for our feelings of sleepiness and fatigue

when we’ve been awake for a very long time.

Caffeine essentially acts to block the effects of adenosine.

It’s a competing agonist, not to get technical,

but it binds to the receptor for adenosine

for some period of time and prevents adenosine

from having its normal pattern of action

and thereby reduces our feelings of fatigue.

But it also increases state of alertness.

So while it’s reducing fatigue,

it’s also pushing on neurochemical systems

in order to directly increase our alertness.

And it does that in large part

by increasing the transmission of epinephrine,

adrenaline in the brain and body.

It also has this interesting effect

of upregulating the number and or efficiency,

or we say the efficacy of dopamine receptors,

such that when dopamine is present

and as a molecule that increases motivation

and craving and pursuit,

that dopamine can have a more potent effect

than it would otherwise.

So caffeine really hits these three systems.

It hits other systems too,

but it mainly reduces fatigue by reducing adenosine,

increases alertness by increasing epinephrine release

or adrenaline release,

I should say both from the adrenals in your body

and from locus coeruleus within the brain.

And it can, in parallel to all that,

increase the action or the efficacy

of the action of dopamine.

So my typical way of approaching learning and memory

would be to drink some caffeine

and then focus really hard on whatever it is

that I’m trying to learn,

try and eliminate distractions,

and then hope, hope, hope,

or try, try, try to remember that information

as best as I could.

And frankly, I felt like it was working pretty well for me.

And typically, if I leveraged other forms of pharmacology

in order to enhance learning and memory,

things like alpha-GPC or phosphatidylserine,

I would do that by taking those things

before I sat down to learn a particular set of information

or before I went off to learn a particular physical skill.

Now, for those of you out there listening to this,

you’re probably thinking, well, okay,

the results of McGaugh and Cahill pointed to the fact

that having adrenaline released after learning something

enhanced learning of that thing.

But a lot of these things like caffeine or alpha-GPC

can increase epinephrine and adrenaline or dopamine

or other molecules in the brain and body

that can enhance memory for a long period of time.

So it makes sense to take it first or even during learning

and then allow that increase to occur.

And the increase will occur over a long period of time

and will enhance learning and memory.

And while that is partially true, it is not entirely true.

And it turns out it’s not optimal.

Work that was done by the McGaugh Laboratory

and other laboratories evaluated

the precise temporal relationship

between neurochemical activation of these pathways

and learning and memory.

And what they did is they had animals and or people,

depending on the experiment, take a drug, could be caffeine,

could be in pill form,

something that would increase adrenaline

or related molecules that create this state of alertness

that are related to emotionality.

And they had them do it either an hour before,

30 minutes before, 10 minutes before,

five minutes before learning

or during the bout of learning, right?

The reading of the information

or the performing of the skill that one is trying to learn

or five minutes, 10 minutes, 15 minutes, 30 minutes,

et cetera, afterwards.

So they looked very precisely at when exactly is best

to evoke this adrenaline release.

And it turns out that the best time window

to evoke the release of these chemicals,

if the goal is to enhance learning and memory

of the material, is either immediately after

or just a few minutes, five, 10, maybe 15 minutes

after you’re repeating that information.

You’re trying to learn that information.

Again, this could be cognitive information

or this could be a physical skill.

Now, this really spits in the face of the way

that most of us approach learning and memory.

Most of us, if we use stimulants like caffeine

or alpha-GPC, we’re taking those before

or during an attempt to learn, not afterwards.

These results point to the fact

that it is after the learning and memory

that you really want to get that big increase

in epinephrine and the related molecules

that will tamp down memory.

So what this means is that if you are currently using

caffeine or other compounds, and we’ll talk about

what those are and safety issues and so forth in a moment,

if you’re using those compounds in order

to enhance learning and memory by taking them before

or during a learning episode, well, then I encourage you

to try and take them either late in the learning episode

or immediately after the learning episode.

Now, given everything I’ve told you up until now,

why would I say late in the learning episode

or immediately after?

Well, when you ingest something by drinking it

or you take it in capsule form, there’s a period of time

before that gets absorbed into the body.

And different substances, such as caffeine,

alpha-GPC, et cetera, are absorbed in from the gut

and into the bloodstream and reach the brain

and trigger these effects in the brain and body

at different rates.

So it’s not instantaneous.

Some have effects within minutes,

others within tens of minutes and so on.

It’s really going to depend on the pharmacology

of those things, and it’s also going to depend

on whether or not you have food in your gut,

what else you happen to have circulating

in your bloodstream, et cetera.

But at a very basic level, we can confidently say

that there are not one, not dozens,

but as I mentioned before, hundreds of studies in animals

and in humans that point to the fact

that triggering the increase of adrenaline late in learning

or immediately after learning is going to be most beneficial

if your goal is to retain that information

for some period of time and to reduce the number

of repetitions required in order to learn that information.

Now, I want to acknowledge that on previous episodes

of this podcast and in appearing on other podcasts,

I’ve talked a lot about things like non-sleep deep rest

and naps and sleep as vital to the learning process.

And I want to emphasize that none

of that information has changed, right?

I don’t look at any of that information differently

as the consequence of what I’m talking about today.

It is still true that the strengthening of connections

in the brain, the literal neuroplasticity,

the changing of the circuits occurs during deep sleep

and non-sleep deep rest.

And it is also true,

and I’ve mentioned these results earlier,

that two papers were published in Cell Reports,

Cell Press Journal, excellent journal

over the last few years showing that brief naps

of about 20 to up to 90 minutes in some period of time

after an attempt to learn can enhance the rate

of learning and memory.

However, those bouts of sleep, the deep sleep that night,

I should say, or those brief naps,

or even the so-called NSDR, as we call it,

non-sleep deep rest that was used to enhance the learning

and memory of particular pieces of information,

either cognitive or physical information or both,

that still can be performed,

but it can be performed some hours later,

even an hour later.

It can be performed two hours later or four hours later.

Remember, it’s in these naps and in deep sleep

that the actual reconfiguration

of the neural circuits occurs,

the strengthening of those neural circuits occurs.

It is not the case that you need to finish a bout

of learning and drop immediately into a nap or sleep.

Some people might do that,

but if you’re really trying to optimize and enhance

and improve your memory, the data from McGaugh and Cahill

and many other laboratories that stemmed out

from their initial work really point to the fact

that the ideal protocol would be focus on the thing

you’re trying to learn very intensely.

There are also some other things like error rates, et cetera.

Please see our episodes on learning.

We have a newsletter on how to learn better.

You can access that at

It’s a zero cost newsletter.

You can grab that PDF.

It lists out the things to do during the learning bout.

Still try and get excellent sleep.

Again, fundamentally important for mental health,

physical health, and performance.

And we can now extend from performance to saying,

including learning and memory.

Nap, if it doesn’t interrupt your nighttime sleep,

naps of anywhere from 10 to 90 minutes

or non-sleep deep rest protocols

will enhance learning and memory.

But we can now add to that, that spiking adrenaline,

provided it can be done in a safe way,

is going to reduce the number of repetitions

required to learn.

And that should be done at the very tail end

or immediately after a learning bout,

which is compatible with all the other protocols

that I mentioned.

And the reason I’m revisiting the stuff about sleep

and non-sleep deep rest,

is I think that some people got the impression

that they need to do that immediately after learning.

And today I’m saying to the contrary,

immediately after learning,

you need to go into a heightened state

of emotionality and alertness.

Now, it’s vitally important to point out

that you do not need pharmacology.

You don’t need caffeine.

You don’t need alpha-GPC.

You don’t need any pharmacologic substance

to spike adrenaline,

unless that’s something that you already are doing

or that you can do safely

or that you know that you can do safely.

And I always say, and I’ll say it again,

I’m not a physician, so I’m not prescribing anything.

I’m a professor, so I profess things.

You need to do what’s safe for you.

So if you’re somebody who’s not used to drinking caffeine

and you suddenly drink four espresso

after trying to learn something,

you are going to have a severe increase in alertness

and probably even anxiety.

If you’re panic attack prone,

please don’t start taking stimulants

in order to learn things better.

Please be safe.

I don’t just say that to protect me.

I say that to protect you.

And I should mention that if you’re not accustomed

to taking something,

you always want to first check with your doctor, of course,

but also move into that gradually, right?

Start with the lowest effective dose,

the minimal effective dose.

And sometimes the minimal effective dose is zero milligrams.

It’s nothing.

Why do I say that?

Well, we already talked about results

where they put people’s arms into an ice bath

in order to evoke adrenaline release.

You are welcome to do that if you want.

In fact, that’s a pretty low cost, zero pharmacology,

at least exogenous pharmacology way

to approach this whole thing.

That’s a way of evoking your own natural epinephrine.

And it turns out also dopamine release.

You could take a cold shower.

You could do an ice bath

or get into a cold circulating bath.

We’ve done several episodes

on the utility of cold for health and performance.

You can find those episodes at

Also the episode with my colleague at Stanford

from the biology department, Dr. Craig Heller.

Lots of protocols in particular in the episode

on cold for health and performance

that describe how best to use the cold shower

or the ice bath or the circulating cold bath

in order to evoke epinephrine and dopamine release.

The point is that the time in which you would want

to do those protocols is after,

ideally immediately after you’re learning about,

meaning when you’re sitting down to learn new information

or after trying to learn some new physical skill.

Now, whether or not that’s compatible

with the other reasons you’re doing deliberate cold exposure

and whether or not that’s compatible

with the other things you’re doing,

that depends on the contour of your lifestyle,

your training, your academic goals,

your learning goals, et cetera.

But if your specific purpose is to enhance learning

and memory, you want to spike adrenaline afterwards.

And so what I’m telling you is you can do that with caffeine.

You can do that with alpha GPC.

You can do that with a combination of caffeine

and alpha GPC if you can do that safely.

Some of you I know are using other forms of pharmacology.

I did a long episode all about ADHD.

I have to just really declare my stance very clearly

that I am not a fan.

I am actually opposed to people using prescription drugs

who are not prescribed those drugs, right,

in order to enhance alertness.

I think there’s a big addictive potential.

There also is a potential to really disrupt

one’s own pharmacology around the dopaminergic system.

However, some of you I know are prescribed things

like ritalin, Adderall, and modafinil

and things of that sort

in order to increase alertness and focus.

So for those of you that are prescribed those things

from a board-certified physician,

you’re going to have to decide

if you’re going to take them before trying to learn

or after trying to learn.

You also have to take into consideration

that some of those drugs are very long-acting,

some are shorter-acting,

and time that according to what you’re trying to learn

and when.

So that’s pharmacology.

But as I’ve mentioned, there are the behavioral protocols.

You can use cold, and cold is an excellent stimulus

because, first of all, it doesn’t involve pharmacology.

Second of all, you can generally access it

at low to zero cost, especially the cold shower approach.

And third, you can titrate it.

You can start with warmer water.

You can make it very, very cold if that’s your thing,

and you’re able to tolerate that safely.

You can make it moderately cold.

How cold should it be in order to evoke adrenaline release?

Well, it should be uncomfortably cold,

but cold enough that you feel like

you really want to get out, but can stay in safely.

That’s going to evoke adrenaline release.

If it quickens your breathing,

if it makes you go wide-eyed,

that’s increasing adrenaline release.

In fact, those effects of going wide-eyed

and quickening of the breathing

and the challenges in thinking clearly,

those are the direct effects of adrenaline

on your brain and body.

And of course, there are other ways to increase adrenaline.

You could go out for a hard run.

You could do any number of things

that would increase adrenaline in your body.

Which things you choose is up to you.

But from a very clear, solid grounding in research data,

we can confidently say that spiking adrenaline

after interacting with some material,

physical or cognitive material that you’re trying to learn

is going to be the best time to spike that adrenaline.

Now, I realize that I’m being a bit redundant today,

or perhaps a lot redundant in repeating over and over

that the increase in epinephrine should occur

either very late in an attempt to learn something

or immediately after an attempt to learn something.

I also want to emphasize the general contour

of pharmacologic effects and of behavioral tools

to create adrenaline.

What do I mean by that sentence?

What I mean is that McGaugh and colleagues

explored a huge number of different compounds and approaches,

everything from the hand into the ice bath

to injecting adrenaline, to caffeine,

to drugs that block the effects of adrenaline and caffeine,

drugs like mucimol and picrotoxin.

Please don’t take those.

These are drugs that reduce

or enhance the amount of adrenaline.

And the overall takeaway

is that anything that increases adrenaline

will increase learning and memory

and will reduce the number of repetitions

required to learn something,

regardless of whether or not that something

has an emotional intensity or not,

provided that that spike in adrenaline

occurs late in the learning or immediately after.

And anything that reduces epinephrine and adrenaline

will impair learning.

And that’s the key and novel piece of information

that I’m adding now,

which is if you’re taking beta blockers, for instance,

or if you’re trying to learn something

and it’s not evoking much of an emotional response

and you’re not using any pharmacology

or other methods to enhance adrenaline release

after learning that thing,

well, you’re not going to learn it very well.

In fact, McGaugh and Cahill did beautiful experiments

in humans looking at how much adrenaline is increased

by varying the emotional intensity of different things

that they were trying to get people to learn,

or by changing the dosage of epinephrine,

or by changing the amount of epinephrine blocker

that they injected, lots and lots of studies.

The key thing to take away from those studies

is that for some people,

adrenaline was increased 600 to 700%.

So six to seven fold over baseline

in the amount of circulating epinephrine or adrenaline.

And keep in mind,

sometimes that increase was due to the actual thing

they were trying to learn being very emotional,

positive or negative emotion.

And sometimes it was because

they were using a pharmacologic approach

or the ice bath approach.

I don’t think they ever used a cold shower approach,

but that would have been a very effective one,

we can be sure.

However, other people had a zero to 10% increase,

so a very small increase in epinephrine.

What we can confidently say on the basis of all those data

is that the more epinephrine release,

the better that people remembered the material.

Over and over again, this was shown,

whether or not it was for cognitive material,

so learning a language, learning a passage of words,

learning mathematics,

or whether or not it was for physical learning.

I want to emphasize something about physical learning

because I know a number of you

are probably drinking a cup of coffee

or having a cup of yerba mate,

or maybe even an energy drink

and taking some alpha GPC or something

before physical exercise.

I’m not saying that’s a bad thing to do

or that you wouldn’t want to do that,

but that’s really to increase alertness.

It won’t enhance learning,

at least not as well as doing those things

after the physical exercise.

Now, again, many of you, including myself,

exercise for sake of the physical benefits of that exercise,

so cardiovascular resistance training,

but we’re not really focused on learning and memory.

So I emphasize this

just so it’s immensely clear to everybody,

if you want to use those approaches of increasing adrenaline

prior to or during physical training,

or cognitive work for that matter, be my guest.

I think that’s perfectly fine, provided that’s safe for you.

It’s only by moving it to late or after the learning

that you’re really shifting the role

of that adrenaline increase

to enhancing memory specifically.

And as a cautionary note,

don’t think that you can push this entire system

to the extreme over and over again,

or chronically as we say, and get away with it.

In other words, you’re not going to be able to take

a alpha GPC and a double espresso,

do your focus bout of work, cognitive or physical work,

and then spike adrenaline again afterwards

and remember that stuff even better, right?

I’m not encouraging you.

In fact, I’m discouraging you

from chronically increasing adrenaline

both during and after a given bout of work

if the goal is to learn.

Why do I say that?

Well, work from McGaugh and Cahill and others

has shown that it’s not the absolute amount of adrenaline

that you release in your brain and body

that matters for enhancing memory.

It’s the amount of adrenaline that you release

relative to the amount of adrenaline

that was in your system just prior,

in particular in the hour or two prior.

So again, it’s the delta, as we say, it’s the difference.

So if you’re going to chronically increase adrenaline,

you’re not going to learn as well.

The real key is to have adrenaline modestly low,

perhaps even just as much as you need

in order to be able to focus on something,

pay attention to it, and then spike it afterwards.

This is immensely important

because while much of what we’re talking about

is actually a form of inducing

a neurochemical acute stress,

meaning a brief and rapid onset of stress,

well, chronic stress,

the chronic elevation of epinephrine and cortisol

is actually detrimental to learning.

And there’s an entire category of literature,

mainly from the work of the great

and sadly the late Bruce McEwen

from the Rockefeller University

and some of his scientific offspring,

like the great Robert Sapolsky,

showing that chronic stress,

chronic elevation of epinephrine

actually inhibits learning and memory

and also can inhibit immune system function.

Whereas acute, right,

sharp increases in adrenaline and cortisol

actually can enhance learning

and indeed can enhance the immune system.

So if you really want to leverage this information,

you might consider getting your brain and body

into a very calm and yet alert state,

so a high attentional state

that will allow you to focus on

what it is that you’re trying to learn.

We know focus is vital for encoding information

and for triggering neuroplasticity,

but remaining calm throughout that time

and then afterwards spiking adrenaline

and allowing adrenaline to have these incredible effects

on reducing the number of repetitions required to learn.

So if you’re like me,

you’re learning about this information,

this beautiful work of McGaugh and Cahill and others

and thinking, wow,

I should perhaps consider spiking my adrenaline

in one form or another at the tail end

or immediately following an attempt to learn something.

And yet we are not the first to have this conversation,

nor were McGaugh and Cahill

or any other researchers that I’ve discussed today

the first to start using this technique.

In fact, there is a beautiful review

that was published just this year,

May of 2022 in the journal Neuron,

Cell Press Journal, excellent journal

called Mechanisms of Memory Under Stress.

And I just want to read to you

the first opening paragraph of this review,

which is as the name suggests,

all about memory and stress.

So here I’m reading and I quote,

in medieval times communities threw young children

in the river when they wanted them

to remember important events.

They believe that throwing a child in the water

after witnessing historic proceedings

would leave a lifelong memory

for the events in the child.

Believe it or not, this is true.

This is a practice that somehow people arrived at.

I don’t know if they were aware

of what adrenaline was probably not,

but somehow in medieval times,

it was understood that spiking adrenaline

or creating a robust emotional experience

after an experience that one hoped a child would learn

would encourage the child’s nervous system.

And they even know what a nervous system was,

but would encourage the brain and body of that child

to remember those particular events.

Very counterintuitive if you ask me,

I would have thought that the kid would remember

only being thrown into the river.

My guess is that they remember that,

but that the idea here anyway

is that they also remember the things

that preceded being thrown into the river.

So both interesting and amusing

and somewhat I should say thought stimulating really

that this is a practice that has been going on

for many hundreds of years.

And we are not the first to start thinking

about using cold water as an adrenaline stimulus,

nor are we the first to start thinking

about using cold water induced adrenaline

as a way to enhance learning and memory.

This has been happening since medieval times.

So up until now, I’ve been talking about

a pretty broad contour of these experiments.

I’ve been talking about the underlying pharmacology,

the role of epinephrine and so forth.

I haven’t really talked a lot

about the underlying neural mechanisms.

So I’m just going to take a minute or two

and describe those for you because they are informative.

We all have a brain structure called the amygdala.

A lot of people think it’s associated with fear,

but it’s actually associated with threat detection

and more generally, and I should say more specifically

with detecting what sorts of events

in the environment are novel

and are linked to particular emotional states,

both positive emotional states

and negative emotional states.

So the neurons in the amygdala are exquisitely good

at figuring out, right, they don’t have their own mind,

but at detecting correlations

between sensory events in the environment

that trigger the release of adrenaline

and what’s going on in the brain.

And because the amygdala is so extensively interconnected

with other areas of the brain,

it basically connects to everything

and everything connects back to it.

The amygdala is in a position

to strengthen particular connections in the brain

very easily provided certain conditions are met.

And those conditions are the ones

we’ve been talking about up until now,

emotional saliency that results in increases

in epinephrine and cortisol

or circulating epinephrine and cortisol being much higher

than it was 10 minutes or 15 minutes before.

And the net effect of the amygdala in this context

is to take whatever patterns of neural activity

preceded that increase in adrenaline and corticosterone

and strengthen those synapses

that were involved in that neural activity.

So the amygdala doesn’t have knowledge.

It’s not a thinking area.

It’s a correlation detector

and it’s correlating neurochemical states

of the brain and body with different patterns

of electrical activity in the brain.

This is important because it really emphasizes the fact

that both negative and positive emotional states

and the different but somewhat overlapping chemical states

that they create are the conditions,

as we say, the AND gates through which memory is laid down.

AND gates will be familiar to those of you

who have done a bit of computer programming.

An AND gate is simply a condition

in which you need one thing and another to happen

in order for a third thing to happen.

So you need epinephrine elevated

and you need robust activity in a particular brain circuit

if in fact that brain circuit is going to be strengthened.

It’s not sufficient to have one or the other.

You need both, hence the name AND gate.

And the amygdala is very good

at establishing these AND gate contingencies.

It’s also a very generic brain structure

in the sense that it doesn’t really care

what sorts of sensory events are involved

provided they correlated in time

with that increase in adrenaline and corticosterone.

This has a wonderful side and a kind of dark side.

The dark side is that PTSD and traumas of various kinds

often involve a increase in adrenaline

because whatever it was that caused the PTSD

was indeed very stressful,

caused these big increases in these chemicals.

And because the amygdala is rather general

in its functions, right?

It’s not tuned or designed in any kind of way

to be specifically active in response

to particular types of sensory events or perceptions.

Well, then what it means is that we can start

to become afraid of entire city blocks

where one bad thing happened in a particular room

of a particular building in a city block.

We can become fearful of any place

that contains a lot of people

if something bad happened to us

in a place that contained a lot of people.

The amygdala is not so much of a splitter,

as we say in science.

We talk about lumpers and splitters.

Lumpers are kind of generalizers, if that’s even a word.

And I think it is,

someone will tell me one way or the other.

And splitters are people that are ultra precise

and specific and nuanced about every little detail.

The amygdala is more of a lumper than a splitter

when it comes to sensory events.

Other areas of the brain only become active

under very, very specific conditions

and only those conditions.

And similarly, epinephrine is just a molecule.

It’s just a chemical that’s circulating

in our brain and body.

There’s no epinephrine specifically for a cold shower

that is distinct from the epinephrine

associated with a bad event,

which is distinct from the epinephrine

associated with a really exciting event

that makes you really alert.

Epinephrine is just a molecule, it’s generic.

And so these systems have a lot of overlap.

And that can explain in large part

why when good things happen in particular locations

and in the company of particular people,

we often generalize to large categories

of people, places, and things.

And when negative things happen in particular circumstances,

we often generalize about people, places, and things

associated with that negative event.

So now I’d like to talk about other tools

that you can leverage

that have been shown in quality peer-reviewed studies

to enhance learning and memory.

And perhaps one of the most potent of those tools

is exercise.

There are numerous studies on this in both animal models

and fortunately now also in humans,

thanks to the beautiful work of people like Wendy Suzuki

from New York University.

Wendy’s lab has identified how exercise works

to enhance learning and memory

and other forms of cognition I should mention,

as well as things that can augment,

can enhance the effects of exercise on learning and memory

and other forms of cognition.

Wendy is going to be a guest on this podcast.

It’s actually the episode that follows this episode

and includes a lot of material

that we have not covered today.

And she’s an incredible scientist

and has some incredible findings

that I know everyone is going to find immensely useful.

In the meantime, I want to talk about

some of the general effects of exercise

on learning and memory that she’s discovered

and that other laboratories have discovered.

If you recall earlier,

I mentioned that learning and memory

almost always involves the strengthening

of particular synapses and neural circuits in the brain,

and not so much the increase

in the number of neurons in the brain.

There is one exception, however,

and we now have both animal data and some human data

to support the fact that cardiovascular exercise

seems to increase what we call dentate gyrus neurogenesis.

Neurogenesis is the creation of new neurons.

The dentate gyrus is a sub-region of the hippocampus

that’s involved in learning and memory of particular kinds,

right, certain types of events,

in particular contextual learning,

but some other things as well,

sometimes involved in spatial learning.

There’s a lot of debate about

exactly what the dentate gyrus does,

but for sake of this discussion,

and I think everyone in the neuroscience community

would agree that the dentate gyrus is important

for memory formation and consolidation.

The dentate gyrus does seem to be one region of the brain,

certainly in the rodent brain,

but more and more it’s seeming also in the human brain

where at least some new neurons

are added throughout the lifespan.

And as it turns out that cardiovascular exercise

can increase the proliferation

of new neurons in this structure,

and that those new neurons, excuse me,

are important for the formation

of certain types of new memories.

There are wonderful data showing that

if you use X irradiation,

which is a way to eliminate the formation of those new cells

or other tools and tricks to eliminate the formation

of those cells, that you block the formation

of certain kinds of learning and memory.

What does this mean?

Well, there are a lot of reasons

for the statement I’m about to make

that extend far beyond neurogenesis

and the hippocampus learning and memory,

but it’s very clear that getting anywhere

from 180, I should say a minimum of 180 to 200 minutes

of so-called zone two cardiovascular exercise.

So this is cardiovascular exercise that can be performed

at a pretty steady state,

which would allow you to just barely hold a conversation.

So breathing hard, but not super hard.

This isn’t sprints or high intensity interval training,

but doing that for 180 to 200 minutes per week total

is it appears the minimum threshold

for enhancing some of the longevity effects

associated with improvements in cardiovascular fitness.

And we believe that it is indirectly,

I should say indirectly through enhancements

in cardiovascular fitness,

that there are improvements

in hippocampal dentate gyrus neurogenesis.

What does that mean?

The improvements in cardiovascular function

are indirectly impacting the ability of the dentate gyrus

to create these new neurons.

To my knowledge, there’s no direct relationship

between exercise and stimulating the production

of new neurons in the brain.

It seems that it’s the improvements in blood flow

that also relate to improvements

in things like glymphatic flow,

the circulation of lymph fluid within the brain

that are enhancing neurogenesis.

And that neurogenesis as it appears is important.

Now, in fairness to the landscape of neuroscience

and my colleagues at Stanford and elsewhere,

there is a lot of debate as to whether or not

there is much if any neurogenesis in the adult human brain.

But regardless, I think the data are quite clear

that the 180 to 200 minutes minimum

of cardiovascular exercise is going to be important

for other health metrics.

Now it is clear that exercise can impact learning and memory

through other non-neurogenesis,

non-new neuron type mechanisms.

And one of the more exciting ones

that has been studied over the years

is this notion of hormones from bone

traveling in the bloodstream to the brain

and enhancing the function of the hippocampus.

The words hormones from bones is surprising to you.

I’m here to tell you that yes, indeed,

your bones make hormones.

We call these endocrine effects.

So in biology, we hear about autocrine,

paracrine, and endocrine.

And those different terms refer to over what distance

a given chemical has an effect on a cell.

For instance, a cell can have an effect on itself.

It can have an effect on immediately neighboring cells

or it can have an effect on both itself,

immediately neighboring cells

and cells far, far away in the body.

And that last example of a given chemical

or substance having an effect on the cell that produced it

plus neighboring cells plus cells far away

is an endocrine effect.

And a lot of hormones, not all work in this fashion.

Hence why we sometimes hear about endocrine and hormone

as kind of synonymous terms.

Your bones make chemicals that travel in the bloodstream

and have these endocrine effects.

So they’re effectively acting as hormones.

And one such chemical is something called osteocalcin.

Now these findings arrived to us through various labs,

but one of the more important labs

for sake of this discussion today

is the laboratory of Eric Kandel

at Columbia Medical School.

Eric is now, I believe in his mid to late nineties,

still very sharp and has studied learning and memory.

It also turns out that he is an avid swimmer.

Now I happen to know that Eric swims anywhere

from a half a mile to a mile a day.

And again, this is anecdata.

This is, I’m not referring to the published data just yet,

but he credits that exercise as one of the ways

in which he keeps his brain sharp

and has indeed kept his brain sharp for many, many decades.

And as I mentioned before, he’s well into his nineties.

So pretty impressive.

His laboratory has studied the effects of exercise

on hippocampal function and memory,

and other laboratories have done that as well.

And what they found is that cardiovascular exercise

and perhaps other forms of exercise too,

but mainly cardiovascular exercise

creates the release of osteocalcin from the bones

that travels to the brain

and to sub-regions of the hippocampus

and encourages the electrical activity

and the formation and maintenance of connections

within the hippocampus

and keeps the hippocampus functioning well

in order to lay down new memories.

Now, osteocalcin has a lot of effects

besides just improving the function of the hippocampus.

Osteocalcin is involved in bone growth itself.

It’s involved in hormone regulation.

In fact, there’s really nice evidence

that it can regulate testosterone and estrogen production

by the testes and ovaries

and a bunch of other effects in other organs of the body.

Because again, it’s acting in this endocrine manner.

It’s arriving from bone to a lot of different organs

to have effects.

Load-bearing exercise in particular

turns out to be important

for inducing the release of osteocalcin.

And when you think about this, it makes sense.

A nervous system exists for a lot of reasons

to sense, perceive, et cetera.

You’ve got taste, you’ve got smell, you’ve got hearing,

but the vast majority of brain real estate,

especially in humans, is dedicated to two things.

One, vision.

We have an enormous amount of brain real estate

devoted to vision, certainly compared to other senses.

And to movement,

the ability to generate coarse movements of the body,

the ability, excuse me,

to generate fine movements of the body,

like the digits or to wink one eye

or to tilt your head in a particular way

or move your lips and move your face

and do all sorts of different things

in a very nuanced and detailed way.

So much of our brain real estate is devoted to movement

that it’s been hypothesized for more than a half century,

but especially in recent years,

as we’ve learned more about the function of the brain

at a really detailed circuit level,

that the relationship between the brain and body

and the maintenance and perhaps even the improvement

of neural circuitry in the brain

depends on our body movements

and the signal from the body that our brain is still moving.

So think about that.

How would your brain know if your body was moving regularly

and how would it know how much it was moving?

And how would it know which limbs it was moving?

Well, you could say, if the heart rate is increased,

then the blood flow will be increased

and then the brain will know.

Ah, but how does your brain know

that it’s increased blood flow due to movement

and not to, for instance, just stress, right?

Maybe you actually can’t move

and you’re very stressed about that.

And so the increased blood flow

is simply a consequence of increased stress.

The fact that osteocalcin is released from bone

and in particular can be released

in response to load bearing exercise.

So this would be running.

Again, weightlifting hasn’t been tested directly,

but one would imagine anything that involves jumping

and landing or weight lifting or body weight movements

and things of that sort.

That’s a signal to release osteocalcin.

And we know that signal occurs

that is directly reflective of the fact

that the body was moving and moving in particular ways.

In fact, you could imagine that big bones like your femur

are going to release more osteocalcin

or be in a position to release more osteocalcin

than fine movements like the movements of the digits.

And this idea that the body is constantly signaling

to the brain about the status of the body

and the varying needs of the brain

to update its brain circuitry is a really attractive idea

that fits entirely with the biology of exercise,

osteocalcin, and hippocampal function.

I do want to mention that I’m not the first

to raise this hypothesis.

This hypothesis actually was discussed

in a fair amount of detail by John Rady,

who’s a professor in Harvard Medical School.

He wrote a book called Spark,

which was one of the early books,

at least from an academic about brain plasticity

and the relationship between exercise

and movement and plasticity.

And John, who I have the good fortune to know,

has described to me experiments,

or I should say observations of species

of ocean dwelling animals that have,

at least for the early part of their life,

a very robust and complicated nervous system.

But then these particular animals are in the habit

of plopping down onto a rock.

They find a kind of a safe, comfy space,

and they actually stick to that rock,

and they don’t move anymore for a certain portion,

I should say the late portion of their life.

And it is at the transition between moving a lot

and being stationary that those animals

actually digest their own brain.

They literally metabolize a good portion

of their nervous system,

because they decide, well, I don’t need this anymore,

and gobble it up, use it for its nutritional value,

and then sit there like a moron version of themselves

with a limited amount of brain tissue,

because they don’t need to move anymore.

Now, I certainly don’t want to give the message

that just moving, just exercise is sufficient

to keep the neural architecture of your brain

healthy, young, and able to learn.

While that might be true,

it’s also important to actually engage

in attempts to learn new material,

either physical material,

so new types of movements and skills,

and or new types of cognitive information,

languages, mathematics, history, current events,

all sorts of things that involve your brain.

Nonetheless, it’s clear that physical movement

and cognitive ability,

and the potential to enhance cognitive ability,

and the ability to learn new physical skills

are intimately connected.

And osteocalcin appears to be at least one way

in which that brain-body relationship

is established and maintained.

So given the information about osteocalcin and movement,

and given the information about spiking adrenaline late,

or after a period of attempt to learn,

you might be asking when is the best time to exercise?

Now, unfortunately, that has not been addressed

in a lot of varying detail

where every sort of variation on the theme

has been carried out.

And yet, Wendy Suzuki’s lab

has done really beautiful experiments

where they have people exercise,

generally it was in the morning,

but at other periods of the day as well.

And what they find is that at least as late as two hours

after that exercise,

there’s an enhancement in learning and memory.

Now, I want to be clear,

we don’t know whether or not that exercise

led to big increases in adrenaline.

It may be that those forms of exercise were modest enough,

or didn’t challenge people enough,

that they merely got a lot of blood flow going,

and that the improvements in learning and memory

were related to blood flow,

and we presume increases in osteocalcin.

However, you could imagine a couple of different

logical protocols based on what we’ve talked about.

Let’s say you were going to do a form of exercise

that was going to spike adrenaline a lot.

So this would be exercise that really challenges

your system and forces you to kind of push through a burn.

Right, so here I’m mainly thinking

about cardiovascular exercise,

but it could even be yoga, it could be resistance training.

If it’s going to give you a big spike in adrenaline,

it’s going to take some serious effort,

then logically speaking,

you would want to place that after a learning bout

in order to increase learning and memory.

However, if you’re using the exercise

in order to enhance blood flow,

and to enhance osteocalcin release

in efforts to augment the function of your hippocampus,

I think it stands to reason that doing that exercise

sometime within the hour to three hours

preceding an attempt to learn makes a lot of sense.

And there I’m basing it on the human data

from Wendy Suzuki’s lab,

I’m basing it on the studies from Eric Kandel

and from others labs.

Again, right now there hasn’t been an evaluation

of a lot of different protocols to arrive at the,

you know, peer reviewed laboratory super protocol.

However, since what we’re talking about

is using activities like exercise that most of us,

probably perhaps all of us should be doing regularly anyway.

And I do believe most, if not all of us

should really regularly be trying to learn

and keep our brain functioning well

and acquire new knowledge

because it’s just a wonderful part of life.

And there is evidence

that that actually can keep your brain young, so to speak.

Well, then exercising either before

or after a learning bout makes a lot of sense

with the emphasis on after a learning bout,

if the form of exercise spikes a lot of adrenaline

for all the reasons we talked about before.

Okay, so we’ve talked about two major categories

of protocols to improve memory

that are grounded in quality peer reviewed science.

And there is yet another third protocol

that we’ll talk about in a few minutes.

But before we do that,

I want to briefly touch on an aspect of memory.

In fact, two aspects of memory

that I get a lot of questions about.

The first one is photographic memory.

To be clear, there are people out there

who have a true photographic memory.

They can look at a page of text,

they can scan it with their eyes

and they can essentially commit that to memory

with very little, if any effort.

While it might seem that having a photographic memory

is a very attractive skill to have,

should caution you against believing that

because it turns out that people

with true photographic memory are often very challenged

at remembering things that they hear

and oftentimes are not so good at learning physical skills.

It’s not always the case, but often that’s the case.

So be careful what you wish for.

If you do have a photographic memory,

there are certain professions

that lend themselves particularly well to you.

And indeed, a lot of people with photographic memory

have to find a profession and have to move through life

in a way that is in concert with that photographic memory.

So again, it’s a super ability, it’s a hyper ability,

and yet it’s not necessarily one

that is desirable for most people.

There’s also this category

of what are called super recognizers.

These people are, I should mention,

highly employable by government agencies.

These are people that have an absolutely astonishing ability

to recognize faces and to match faces to templates.

They can look at a photograph of say somebody

on a most wanted list,

and then they can look at video footage

of let’s say an airport or a mall or a city street

at fairly low resolution,

and they can spot the person whose face matches

that photograph that they looked at.

Even if that video or other footage

is of people’s profiles or even the tops of their heads

or even just a portion of their forehead,

these people have just an incredible ability

to recognize faces and to template match.

And again, these people often will take jobs with agencies

where this sort of thing is important.

Some of you out there probably are super recognizers

and may or may not notice it.

If you’ve ever had the experience of watching a movie

and thought to yourself,

wow, her mouth looks so much like my cousin’s mouth,

or you look at a character in a movie or television show,

and you think, wow,

they look almost like the younger sister of so-and-so,

well, then it’s very likely that you have this,

or at least a mild form of this super recognizer ability.

That is not memory per se.

That is the hyper-functioning of an area of the brain

that we call the fusiform gyrus.

The fusiform gyrus is literally a face recognition area

and a face template matching area,

and it harbors neurons that respond to faces generally.

So as humans and other non-human primates

care a lot about faces and their emotional content

and the identity of faces is super important to us

for all the kinds of reasons that are probably obvious,

knowing who’s friend, who’s foe, who do you know well,

who’s famous, who’s not famous, et cetera.

That is not memory per se.

And yet, if you’re a super recognizer,

or I guess we could call it a moderate face recognizer

or not very good at recognizing faces,

because indeed there are some people

that are kind of face blind.

They don’t actually recognize people

when they walk in the room.

I used to work with somebody like this.

I’d walk into his office and he’d say,

are you rich or are you Andrew?

I’d say, well, am I rich rich?

Like, you know, wealth rich?


And he’d say, no, are you Richard or are you Andrew?

And I’d say, I’m Andrew.

We know each other really well.

He’d say, oh, I’m sorry, I’m kind of face blind.

And it actually tended to be better or worse

depending on how much he was working.

Ironically, the more rested he was,

the more face blind he would become.

So it wasn’t a sleep deprivation thing.

That exists, that’s out there.

There’s the full constellation

of people’s ability to recognize faces.

That’s not really memory.

And yet visual function is a profoundly powerful way

in which we can enhance our memory.

So whether or not you’re a super recognizer of faces,

whether or not you are face blind or anything in between.

Next, I’m going to tell you about a study

which points out the immense value of visual images

for laying down memories.

And you can leverage this information.

And this involves both the taking a photograph,

something that’s actually quite easily done these days

with your phone,

as well as your ability to take mental photographs

by literally snapping your eyelids shut.

So I just briefly want to describe this paper

because it provides a tool that you can leverage

in your attempt to learn and remember things better.

The title of this paper is Photographic Memory,

the effects of our volitional photo-taking

on memory for visual and auditory aspects of an experience.

I really like this paper

because it refers to photographic memory,

not in the context of photographic memory

that we normally hear about

where people are truly photographic,

look at a page and somehow absorb all that information

and commit it to memory,

but rather the use of camera photographs

or the use of mental camera photographs,

literally looking at something and deciding blink

and snapping a, so to speak, snapping a snapshot

of whatever it is that you were looking at

and remembering the content.

The reason I like this paper

and the reason I’m attracted to this issue

of mental snapshots is this is something

that I’ve been doing since I was a kid.

I don’t know why I started doing it,

but every once in a while,

I would say maybe twice a year,

I would look at something

and decide to just snap a mental snapshot of it.

And I’ve maintained very clear memories

of those visual scenes.

Two years ago, I was in an Uber and I looked out the window

and it was a street scene.

I was actually in New York at the time.

And I decided for reasons that are still unclear to me

to take a mental snapshot of this city street image,

even though nothing interesting in particular was happening.

And I do recall that there was a guy wearing a yellow shirt,

walking, there was some construction, et cetera.

I can still see that image in my mind’s eye

because I took this mental snapshot.

This paper addresses whether or not

this mental snapshotting thing is real.

And this is something that I think a lot of people

will resonate with,

whether or not the constant taking of pictures

on our phones or with other devices

is either improving or degrading our memory.

You can imagine an argument for both.

A lot of people are taking pictures

that they never look at again.

And so in a sense,

they’re outsourcing their visual memory of events

into their phone or to some other device,

and they’re not ever accessing the actual image again.

They’re not looking at it, right?

You’re not printing out those photos.

You’re not scanning through your phone again.

Sometimes you might do that, but most of the time,

people don’t.

Most of the photographs that people are taking,

they’re not revisiting again.

So the motivation for this study

was that previous experiments had shown

that if people take photos of a scene or a person

or an object, that they are actually less good

at remembering the details of that scene or object, et cetera.

This study challenged that idea and raised the hypothesis

that if people are allowed to choose

what they take photos of, that taking photos,

and again, this is with a camera, not mental snapshotting,

that taking those photos would actually enhance their memory

for those objects, those places, those people,

and in fact, details of those objects, places, and people.

And indeed, that’s what they found.

So in contrast to previous studies

where people had been more or less told,

take photos of these following objects

or these following people or these following places,

and then they were given a memory test at some point later,

in this study, people were given volitional control, right?

They were given agency in making the decision

of what to take photos of.

And I’ll just summarize the results.

We’ll provide a link to this study.

Should say that some of the stuff that they tested

was actually pretty challenging.

Some of them were pottery and other forms of ceramics

that are of the sort that you see

if you go to a big museum in a big city.

And if you’ve ever done that

and you see all the different objects,

there are a lot of details in those objects

and a lot of those objects look a lot alike.

And so, some will have two handles,

some will have one handle, the position of the handles,

how broad or narrow these things are.

You know, a lot of this is pretty detailed stuff.

They also took photos of other things.

So basically what they found was that

if people take pictures of things

and they choose which things they’re taking pictures of,

right, it’s up to them, it’s volitional,

that there’s enhanced memory for those objects later on.

However, it degraded their ability

to remember auditory information.

So what this means is that when we take a picture

of something or a person,

we are stamping down a visual memory of that thing,

and that makes sense, it’s a photograph after all,

but we are actually inhibiting our ability

to remember the auditory, the sound components

of that visual scene or what the person was saying.

Very interesting, and points to the fact

that the visual system can out-compete the auditory system,

at least in terms of how the hippocampus

is encoding this information.

The other finding I find particularly interesting

within this study is that it didn’t matter

whether or not they ever looked at the photos again.

So they actually had people take photos

or not take photos of different objects.

They had some people keep their photos

and they had other people delete their photos,

and it turns out that whether or not people kept the photos

or deleted those photos had no bearing

on whether or not they were better or worse

at remembering things, they were always better

at remembering them as compared to not taking photos of them.

What does this mean?

It means that if you really want to remember something

or somebody, take a photo of that thing or person,

pay attention while you take the photo,

but it doesn’t really matter if you look at the photo again,

somehow the process of taking that photo,

probably looking at it, you know, in a camera,

typically we’d say through the viewfinder

or now because of digital cameras on the screen,

on the back of that camera or on your phone,

that framing up of the photograph

stamps down a visual image in your mind

that is more robust at serving a memory

than had you just looked at that thing

with your own eyes, very interesting.

And it raises all sorts of questions for me

about whether or not it’s because you’re framing up

a small aperture, a small portion of the visual scene,

that’s one logical interpretation,

although they didn’t test that.

I should also say that they found that whether or not

you looked at a photo that you took

or whether or not you deleted it

and never looked at it again,

didn’t just enhance visual memory

or the memory for the visual components of that image,

but it always reduced your ability

to remember sounds associated with that experience.

So that’s interesting.

And then last but not least,

and perhaps most interesting, at least to me,

was the fact that you didn’t even need a camera

to see this effect.

If subjects looked at something

and took a mental photograph of that thing,

it enhanced their visual memory of that thing

significantly more than had they not taken a mental picture.

In fact, it increased their memory of that thing

almost as much as taking an actual photograph

with an actual camera.

And the reason I find this so interesting

is that a lot of what we try and learn is visual.

And for a lot of people,

the ability to learn visual information feels challenging.

And we’ll look at something

and we’ll try and create some detailed understanding of it.

We’ll try and understand the relationships

between things in that scene.

It does appear based on the study

that the mere decision to take a mental snapshot,

like, okay, I’m going to blink my eyelids

and I’m going to take a snapshot of whatever it is I see,

can actually stamp down a visual memory

much in the same way that a camera

can stamp down a visual memory,

of course, through vastly distinct mechanisms.

No discussion of memory would be complete

without a discussion of the ever intriguing phenomenon

known as deja vu.

This sense that we’ve experienced something before,

but we can’t quite put our finger on it.

Where and when did it happen?

Or the sense that we’ve been someplace before

or that we are in a familiar state or place

or context of some kind.

Now, I’ve talked about this on the podcast before,

at least I think I have.

And the way this works has been defined

largely by the wonderful work of Susumu Tonegawa

at Massachusetts Institute of Technology, MIT.

Susumu collected a Nobel prize quite appropriately

for his beautiful work on immunology.

And he’s also a highly accomplished neuroscientist

who studies memory and learning and deja vu.

And I should also mention the beautiful work

of Mark Mayford at the Scripps Institute and UC San Diego.

Beautiful work on this notion of deja vu.

Here’s what they discovered.

They evaluated the patterns of neural firing

in the hippocampus as subjects learn new things.


So neuron A fires, then neuron B fires,

then neuron C fires in a particular sequence.

Again, the firing of neurons in a particular sequence,

like the playing of keys on a piano in a particular sequence

leads to a particular song on the piano

and leads to a particular memory

of an experience within the brain.

They then used some molecular tools and tricks

to label and capture those neurons

such that they could go back later

and activate those neurons in either the same sequence

or in a different sequence to the one that occurred

during the formation of the memory.

And to make a long story short

and to summarize multiple papers

published in incredibly high tier journals,

journals like Nature and Science,

which are extremely stringent,

found that whether or not those particular neurons

were played in the precise sequence

that happened when they encoded the memory

or whether or not those neurons were played

in a different sequence,

or even if those neurons were played, activated that is,

all at once with no temporal sequence,

all firing in concert all at once,

evoked the same behavior

and in some sense, the same memory.

So at a neural circuit level, this is deja vu.

This is a different pattern of firing

of neurons in the brain,

leading to the same sense of what happened,

leading to a particular emotional state or behavior.

Now, whether or not the same sort of phenomenon occurs

when you’re walking down the street

and suddenly you feel as if,

wow, I feel like I’ve been here before.

You meet someone and you feel like,

gosh, I feel like I know you.

I feel like there’s some familiarity here

that I can’t quite put my finger on.

We don’t know for sure that that’s what’s happening,

but this is the most mechanistic and logical explanation

for what has for many decades, if not hundreds of years,

has been described as deja vu.

So for those of you that experienced deja vu often,

just know that this reflects a normal pattern

of encoding experiences and events within your hippocampus.

I’m not aware of any pathological situations

where the presence of deja vu inhibits daily life.

Some people like the sensation of deja vu.

Other people don’t.

Almost everybody, however, describes it as somewhat eerie.

This idea that even though you’re in a very different place,

even though you’re interacting with a very different person

that you could somehow feel as if this has happened before.

And just realize this, that your hippocampus,

while it is exquisitely good at encoding

new types of perceptions, new experiences, new emotions,

new contingencies and relationships of life events,

it is not infinitely large,

nor does it have an infinite bucket

full of different options of different sequences

for those neurons to play.

So in a lot of ways, it makes perfect sense

that sometimes we would feel as if a given experience

had happened previously.

I’d like to cover one additional tool

that you can use to improve learning and memory.

And I should mention, this is a particularly powerful one.

And it’s one that I’m definitely going to employ myself.

This is based on a paper from none other than Wendy Suzuki

at New York University.

We talked about her a little bit earlier.

And again, she’s going to be on the podcast

in our next episode and is just an incredible researcher.

I’ve known Wendy for a number of years,

and it’s only in the last, I would say five or six years

that she’s really shifted her laboratory

toward generating protocols that human beings can use.

And she’s putting that to great effect,

great positive effect, I should say,

publishing papers of the sort that I’m about to describe,

but also incorporating some of these tools and protocols

into the learning curriculum

and the lifestyle curriculum of students at NYU,

which I think is a terrific initiative.

So you don’t need to be an NYU student

in order to benefit from her work.

I’m going to tell you about some of that work now,

and she’ll tell you about this and much more

in the episode that follows this one.

The title of this paper will tell you a lot

about where we’re going.

The title is,

Brief Daily Meditation Enhances Attention, Memory,

Mood, and Emotional Regulation

in Non-Experienced Meditators.

If ever there was an incentive to meditate,

it is the data contained within this paper.

I want to briefly describe the study,

and then I also want to emphasize

that when you meditate is absolutely critical.

I’ll talk about that just at the end.

This is a study that involves subjects aged 18 to 45,

none of whom were experienced meditators

prior to this study.

There were two general groups in this study.

One group did a 13 minute long meditation,

and this meditation was a fairly conventional meditation.

They would sit or lie down.

They would do somewhat of a body scan,

evaluating, for instance,

how tense or relaxed they felt throughout their body,

and they would focus on their breathing,

trying to bring their attention back to their breathing

and to the state of their body as the meditation progressed.

The other group, which we can call the control group,

listened to, of all things, a podcast.

They did not listen to this podcast.

They listened to Radiolab, which is a popular podcast

for an equivalent amount of time,

but they were not instructed to do any kind of body scan

or pay attention to their breathing.

Every subject in the study either meditated daily

or listened to a equivalent duration podcast daily

for a period of eight weeks.

And the experimenters measured a large number of things,

of variables, as we say.

They looked at measures of emotion regulation.

They actually measured cortisol, a stress hormone.

They measured, as the title suggests,

attention and memory and so forth.

And the basic takeaway of the study is that eight weeks,

but not four weeks,

of this daily 13-minute-a-day meditation

had a significant effect in improving attention,

memory, mood, and emotion regulation.

I find this study to be very interesting

and, in fact, important because most of us have heard

about the positive effects of meditation

on things like stress reduction

or on things such as improving sleep.

And I want to come back to sleep in a few moments

because it turns out to be a very important feature

of this study.

This particular study I like so much

because they used a really broad array

of measurements for cognitive function.

Things like the Wisconsin card sorting task.

I’m not going to go into this.

Things like the Stroop task.

And they also, as I mentioned, measured cortisol

and many other things, including, not surprisingly, memory

and people’s ability to remember

certain types of information.

In fact, varied types of information.

And the basic takeaway was, again,

that you could get really robust improvements

in learning and memory, mood, and attention

from just 13 minutes a day of meditation.

Now, there’s an important twist in this study

that I want to emphasize.

If you read into the discussion of this study,

it’s mentioned that somehow meditation did not improve

but actually impaired sleep quality

compared to the control subjects.

You might think, wow, why would that be?

I mean, meditation is supposed to reduce our stress.

Stress is supposed to inhibit sleep.

And therefore, why would sleep get worse?

Well, what’s interesting is the time of day

when most of these subjects tended to do their meditation.

Most of the subjects in this study

did their meditation late in the day.

This is often the case in experiments.

I know this because we run experiments

with human subjects in my laboratory

and people are paid some amount of money

in order to participate

or they’re given something as compensation

for being in the study.

But oftentimes the meditation, or in the case of my lab,

the respiration work or other kinds of things

that they’re assigned to do are not their top, top priority.

And we understand this.

But in this study, the majority of subjects,

here I’m reading,

completed their meditation sessions

from somewhere between 8 and 11 p.m.

and sometimes even between 12 and 3 a.m.

I think there probably were a lot of college students

enrolled in this study

and their hours often are late shifted.

That impaired sleep,

and this raises a bigger theme that I think is important

many times before on this podcast

and certainly in the episode on mastering sleep

and conquering or mastering stress.

Those episodes, we talked about the value again

of these non-sleep deep rest protocols, NSDR,

for reducing the activity of your sympathetic nervous system

the alertness, so-called stress arm

of your autonomic nervous system

that makes you feel really alert.

NSDR is superb for reducing your level of alertness,

increasing your level of calmness

and putting you into a so-called

more parasympathetic relaxed state.

Meditation does that too, but it also increases attention.

If you think about meditation,

meditation involves focusing on your breath

and constantly focusing back on your breath

and trying to avoid the distraction

of things you’re thinking or things that you’re hearing

and coming so-called back to your body, back to your breath.

So meditation is actually has a high attentional load.

It requires a lot of prefrontal cortical activity

that’s involved in attention,

which then logically relates

to the one of the outcomes of this study,

which is that attention abilities improved

in daily meditators.

It also points out that increasing the level of attention

and the activity of your prefrontal cortex may,

and I want to emphasize may because I’m here,

I’m speculating about the underlying mechanism,

inhibit your ability to fall asleep.

So while we have meditation on the one hand

that does tend to put us into a calm state,

but it is a calm, very focused state.

In fact, attention and focus are inherent

to most forms of meditation.

Non-sleep deep rest, such as yoga nidra,

as some of you know it to be, or NSDR.

There’s a terrific NSDR script that’s available free online

that’s put out by Made For,

so you can go to YouTube, NSDR Made For.

You can also just do a search for NSDR.

There are a number of these available out there,

again, at no cost.

Those NSDR protocols tend to put people

into a state of deep relaxation,

but also very low attention.

And we have to assume very low activation

of the prefrontal cortex.

So the takeaways from the study are several fold.

First of all, that daily meditation of 13 minutes

can enhance your ability to pay attention and to learn.

It can truly enhance memory.

However, you need to do that for at least eight weeks

in order to start to see the effects to occur.

And we have to presume that you have to continue

those meditation training sessions.

In fact, they found that if people only did four weeks

of meditation, these effects didn’t show up.

Now, eight weeks might seem like a long time,

but I think that 13 minutes a day

is not actually that big of a time commitment.

And the results of this study certainly incentivize me

to start adopting a, I’m going for 15 minutes a day now.

I’ve been a on and off meditator for a number of years.

I’ve been pretty good about it lately,

but I confess I’ve been doing far shorter meditations

of anywhere from three to five or maybe 10 minutes.

I’m going to ramp that up to 15 minutes a day.

And I’m doing that specifically to try and access

these improvements in cognitive ability

and our abilities to learn.

Also based on the data in this paper,

I’m going to do those meditation sessions

either early in the day,

such as immediately after waking or close to it.

I might get my sunshine first.

I’m, as you all know,

very big on getting sunlight in the eyes early in the day,

as much as one can and as early as one can

once the sun is out,

but certainly doing it early in the day

and not past 5 p.m. or so in order to make sure

that I don’t inhibit sleep.

Because I think this result that they describe

of meditation inhibiting quality sleep

compared to controls is an important one

to pay attention to, no pun intended.

Today, we covered a lot of aspects of memory

and how to improve your memory.

We talked about the different forms of memory

and we talked about some of the underlying neural circuitry

of memory formation.

And we talked about how the emotional saliency

and intensity of what you’re trying to learn

has a profound impact on whether or not you learn

in response to some sort of experience,

whether or not that experience is reading or mathematics

or music or language or a physical skill, doesn’t matter.

The more intense of an emotional state that you’re in

in the period immediately following that learning,

the more likely you are to remember

whatever it is that you’re trying to learn.

And we talked about the neurochemicals

that explain that effect,

about epinephrine and corticosterones like cortisol

and how adjusting the timing of those is so key

to enhancing your memory.

And we talked about the different ways

to enhance those chemicals.

Everything ranging from cold water to pharmacology

and even just adjusting the emotional state

within your mind in order to stamp down

and remember experiences better.

We also talked about how to leverage exercise

in particular load-bearing exercise

in order to evoke the release of hormones like osteocalcin,

which can travel from your bones to your brain

and enhance your ability to learn.

And we talked about a new form of photographic memory,

not the traditional type of photographic memory

in which people can remember everything they look at

very easily, but rather taking mental snapshots

of things that you see.

Again, emphasizing that that will create a better memory

of what you see when you take that mental snapshot,

but will actually reduce your memory

for the things that you hear at that moment.

And we discussed the really exciting data

looking at how particular meditation protocols

can enhance memory, but also attention and mood.

However, if done too late in the day,

can actually disrupt sleep

precisely because those meditation protocols

can enhance attention.

Now, I know that many of you are interested

in neurochemicals that can enhance learning and memory.

And I intend to cover those in deep detail

in a future episode.

However, for sake of what was discussed today,

please understand that any number

of different neurochemicals can evoke

or can increase the amount of adrenaline

that’s circulating in your brain and body.

And it’s less important how one accesses

that increase in adrenaline, right?

Again, this can be done through behavioral protocols

or through pharmacology.

Assuming that those behavioral protocols

and pharmacology are safe for you,

it really doesn’t matter how you evoke

the adrenaline release, because remember,

adrenaline is the final common pathway

by which particular experiences,

particular perceptions are stamped into memory,

which answers our very first question

raised at the beginning of the episode,

which is why do we remember anything at all, right?

That was the question that we raised.

Why is it that from morning till night

and throughout your entire life,

you have tons of sensory experience, tons of perceptions.

Why is it that some are remembered and others are not?

While I would never want to distill an important question

such as that down to a one molecule type of answer,

I think we can confidently say based on the vast amount

of animal and human research data that epinephrine,

adrenaline, and some of the other chemicals

that it acts with in concert is in fact the way

that we remember particular events and not all events.

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During today’s episode and on many previous episodes

of the Huberman Lab podcast, we discuss supplements.

While supplements aren’t necessary for everybody,

many people derive tremendous benefit from them

for things like enhancing sleep and focus,

and indeed for learning and memory.

For that reason, the Huberman Lab podcast

is now partnered with Momentus Supplements.

The reason we partnered with Momentus is several fold.

First of all, we wanted to have one location

where people could go to access single ingredient,

high quality versions of the supplements

that we were discussing on this podcast.

This is a critical issue.

A lot of supplement companies out there

sell excellent supplements,

but they combine different ingredients

into different formulations,

which make it very hard to figure out

exactly what works for you

and to arrive at the minimal effective dose

of the various compounds that are best for you,

which we think is extremely important.

And that’s certainly the most scientific way

or rigorous way to approach

any kind of supplementation regimen.

So Momentus has made these single ingredient formulations

on the basis of what we suggested to them.

And I’m happy to say they also ship internationally.

So whether or not you’re in the US or abroad,

they’ll ship to you.

If you’d like to see the supplements recommended

on the Huberman Lab podcast,

you can go to slash Huberman.

They’ve started to assemble the supplements

that we’ve talked about on the podcast.

And in the upcoming weeks,

they will be adding many more supplements

such that in a brief period of time,

most if not all of the compounds

that are discussed on this podcast

will be there again in single ingredient,

extremely high quality formulations

that you can use to arrive

at the best supplement protocols for you.

We also include behavioral protocols

that can be combined with supplementation protocols

in order to deliver the maximum effect.

Once again, that’s slash Huberman.

And if you’re not already following us

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it’s Huberman Lab on both Twitter and Instagram.

There, I describe science and science-related tools,

some of which overlap with the content

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but much of which is distinct

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We also have a newsletter

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That newsletter provides summary protocols

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You can also see some sample newsletters,

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Once again, thank you for joining me today

to discuss the neurobiology of learning and memory

and how to improve your memory using science-based tools.

And last, but certainly not least,

thank you for your interest in science.



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