Let's talk about brains! Hi my name is Bing Brunton
and I'm a neuroscientist at the University of Washington in Seattle. In this video I'm going to
introduce to you the next series of videos that comprise a university level course:
"Introduction to Neuroscience". This is a course that I've taught several times at the University of Washington, and I'm going to talk to you about the topics we're going to cover as well as my expectations and
hopes for you in terms of what you'll get out of taking this course. Now I love teaching this
course this is one of my favorite things to do and introducing Neuroscience to people who
are not yet neuroscientists maybe some of you will be inspired to become neuroscientists and
the reason I love talking about it so much is because Neuroscience is such an interdisciplinary
field that I get to talk not only about biology but about how Neuroscience connects with almost
everything else that you can think of and this includes a lot of different Sciences we
have connections to physics to chemistry to psychology and as well as connections to
engineering applications to health as well as to your sense of self and philosophy and legal
ramifications of what we know about fundamentals of neurobiology before we get we get all of that
I wanted to talk first about my brain and you can use where we all start right we're using
our brains to understand each other right now so the mammalian brain the human brain looks
something like this there's a picture of it on the bottom here and you can look at it and
you can kind of compare it to some of the other mammalian brains that are in the animals that are
in the world around us and welcome to tell you is that the mammalian brain is a lot in common with
other type of Malian brains but there's also some key differences as well in particular the human
brain weighs about one and a half kilograms and it has 86 billion neurons-ish now what does
this actually mean right this is so these are just numbers here what does this actually mean
so what I want you to do is take your two Fists make two fists and put them together go ahead
and do it yourself if you look then at your hands put together as two fists this is going to
be approximately the size of your brain stuffed inside your skull now I don't know about you the
first time I did it very first time I did this I was surprised at how small it is maybe I have a
big head I don't really know who knows what that means I also know that some of you are going to
have larger hands than others don't take it too seriously this is only approximately how big your
brain is now we know the brain is really important for a lot of different reasons and one of the
reasons is because even though for an adult human the brain weighs approximately two percent of your
body mass at rest it occupies approximately 20 percent of your metabolic costs so about 20 of the
calories you're burning at any particular moment when you're not doing anything this is not true
if you're running a marathon it's devoted to just keeping the brain alive and functioning and ready
to do the next thing that is getting ready to do so that's one indication of how important it is
now a few more things about the brain that I think are really interesting just I like thinking about
size skills and time skills the brain has this wrinkly bits on the outside we'll have a later
video talking about exactly what those are and why they're there the short version of the story
is that that's what you're looking at is a very outer layer of the brain called the cortex it's
kind of like a helmetus on the outside and it's wrinkly because it's actually a two-dimensional
sheet approximately that's quite a bit larger than what you can stuff inside your skull if you took
it out if you took the cortex out shook it out and ironed it you get a sheet that is uh well you know
it's actually approximately the size of a towel a small hand towel like this one right so if you can
kind of Imagine wrinkling it up and then stuffing inside your head I don't remember actually doing
this that's approximately how large your cortex is I told you the cortex is also a two-dimensional
sheet so what does that mean well it's actually remarkably thin um I have a something like a
credit card okay so if you take any credit card and look at it you can see how thin it is
that's approximately two millimeters so the entire cortex is about that thin and in fact the
size of a regular credit card is about the size of your primary visual cortex if you imagine
taking one of these credit cards folding in half and then stuffing the back of your brain
that is the size of your primary visual cortex so those are kind of cool things that I like to
telling people the first time I introduced them to brains but Anatomy is only a very small part of
our understanding of Neuroscience and neurobiology so as a neuroscientist I happen to be a
type of neuroscientist called computational neuroscientists and what that means is that I
really like thinking about mathematical models and different ways that we can analyze data from
both brain and behavior and so rather than giving you a syllabus first what I'm going to tell you
first is my perspective why I'm a neuroscientist how it is that I feel like this is a really
interesting thing that's going to occupy not only the rest of my career but hopefully the
careers of lots of other people in the world as well so from my perspective one of the coolest
things about Neuroscience is that the brain has multi-scale structures in space now I'm going to
break that down and tell you what I mean by that phrase what we're looking at here on the vertical
axis is what's called a logarithmic accessing size and so every tick mark is 10 times larger as we
go up okay so right here is a millimeter we have a thousands of a millimeter and then we have a
meter up here so the reason that the brain is cool one of the reasons brain is cool is because it has
really cool interesting structures that are worth studying at every single scale of description the
smallest thing that we sometimes think about in Neuroscience is the size of a synapse so the
cells of your brain are called neurons and neurons talk to each other at these Junctions
called synapses the male in the human brain has 86 billion neurons on average every neuron
in your brain makes a thousand to ten thousand synapses with other neurons and so there's a ton
of these things inside your brain right now we're only looking at one of them now despite having
lots and lots of them and you see these really tiny structures they're in fact extraordinarily
complicated and very very cool there's going to be a video all about the synapse later on it is
so cool that you think about the infrastructure that goes into running and keeping alive and
functioning one of these synapses it has the complexity of a small City we have things like
roads we have garbage collection we have power plants we have recycling plants even this is very
green here and that is only one synapse among all of the synapses that go into running your brain
and your nervous system but of course that's not all because every neuron and you might even see
pictures of neurons like a couple of drawings of the ones over there neurons are also cool because
they actually have non-trivial geometry they're not blobs like generic eukaryotic cells and you
might have learned about when you first learned about cells in grade school they're very much not
spherical and in fact they're so not spherical that they have these beautiful dendritic and
arsonic arborizations that very much look like the way that trees reach into the sky and their
root systems reach into the ground those are just individual neurons neurons talk to each other
and form networks of neurons that get larger and larger and larger and and so a lot of things
that we talk about in systems Neuroscience are how all of those networks are coordinated how do they
work together and give rise to what we think of as thoughts and memory and our sense of identity and
of course your nervous system at some point has to run the rest of your body so you're not just the
brain in the jar Thinking by yourself you also have to run a body and so your central nervous
system your brain and your spine innervates the rest of your body which is on the order of a meter
and so that includes summarizing Sensations from all over your body as well as controlling the
muscles and other inter and terrorists your internal organs and running all of those different
structures by the nervous impulses of your nervous system so I'm going to tell you one of my
favorite cocktail party Neuroscience facts the next time you find yourself as a fancy cocktail
party you can share this with your friends the brain is really cool and these neurons have really
interesting shapes and they're really long and thin sometimes what takes the cake is that you
have a neuron that is super thin and very very long and it's so long that it's practically as
tall as you are in particular it is a sensory neuron called the dorsal root ganglion cell and
there's one that's in the very last segment of your spinal column kind of where your tailbone
is in the very back of your spine one end of this neuron innervates the tip of your toe so
it carries sensory information from your Tippy Toe big toe the other end of the cell goes all
the way up to your brain stem to the very back of where your head meets your neck in other words
if you think about this neuron it goes all the way from your toe to your head and it's practically
as tall as you are I think that's super cool what makes it cooler is that this cell is not
something that's very much unique to humans in fact presumably all vertebrates have it so if
you're a giraffe there is a same cell the door through a ganglion cell that goes from its
toe all the way up to the base of its neck try to imagine this for a whale try
to imagine this for extinct dinosaurs now the field of paleoneuroscience is fascinating
um and you can and you can kind of imagine that how difficult it would be to study but if the
nervous system of these extinct dinosaurs are the same that it is for all EX for um all
vertebrates that exist in in the in our life right now then presumably that this dinosaur
had one of these neurons as well and so that probably takes the record for the longest cell
that has likely existed in the history of life so I'm now told you about how the brain has
multi-straw structures in space and how that's super cool and interesting you can you can spend
a lifetime working at any single one of the size scales right but there's cool stuff at every one
of them but there's more because not only does the brain have multi-scale structures in space it
also has multi-scale Dynamics in time now as a computational neuroscientist I love dynamical
systems I love writing models that changing time and this is one of the things that I was
actually drew me to Neuroscience into the study of neurobiology in the first place the fact that
we can write down these really beautiful equations that not only describe Dynamics at any single time
scale but actually allow us the ability to tie them together to describe multi-scale Dynamics in
time once again just like on the previous plot we have a logarithmic plot this time it's in time
so every tick mark is actually 10 times longer on the very far end we have a millisecond which
is usually the time scale on which the smallest times going which three systems Neuroscience talk
about because it is about the length of an action potential the action potential is going to be
the top think of a whole series of videos for the first section of these uh this this video course
and you'll learn all about it the basic point is that the action potential is the fundamental
unit of communication for the electrically active neuron and the actual potential is characteristic
shape occupies approximately one millisecond now of course as we go longer and longer and longer
there's cool things happening at every scale of description in time we have things like
neuromodulation and synaptic plasticity the fact that the synapses how neurons talk to
each other are able to change rapidly as well as slowly throughout your day throughout your
week okay and in order to produce speech in order to move my arms and produce Sensational
movement requires coordination of dynamics of neurons on the order of tens of milliseconds
to seconds we then have things that occupy a little bit longer in time like short-term memory
and long-term memory your brain and your nervous system just like many other parts of your body
are prone to having cyclic variations that are Acadian Rhythm seasonal rhythms hormonal rhythms
in thinking about neurogenesis the fact that in over your lifetime you actually do produce some
numbers of neurons that get incorporated into your nervous systems you're not stuck with just
the ones that you were born with and of course we can talk about long-term learning and memory both
procedural memory as well as memory of things that you know such as the fundamentals of neurobiology
that you're going to be learning about a human lives or on the order of decades right and so
I feel like I'm kind of the same person I was when I was when I was 10 years old there's
some continuity there but in reality I don't share a lot of cells and proteins in common with
that person and so how it is that we have these long-term memories and learn things over time
that is something that we can think about in the context of Neuroscience and neurobiology as well
so those are some of uh the reasons that I really like neuroscience and if you wanted to come on
this adventure with me I'm going to tell you about the topics that we're going to talk about all
right I'm going to start slow and talk about the fundamentals of neurophysiology of a single Neuron
a single cell of the brain and nervous system brains occupy a really cool space because it
fundamentally communicates with each other by using electricity so we're going to be talking
about in a series of First videos electrical properties of a neuron how it is we generate
an action potential how the action potential propagates and how they act a potential
translates to communication among different neurons through different types of synopsis and so
this part is going to be approximately 10 videos the second part we're going to go a little bit
longer in time and also larger in size scales kind of moving up and to the right in those axes
that we had before thinking about the organization of the nervous system both the central as well
as peripheral neurosystem we're going to talk about all of the different sensory systems vision
olfaction for example it's as well as some unusual ones like your sense of time and of course nothing
really happens without movement so we're going to talk about the Neuroscience of movement as well
as motor control how does your motor neurons activate and um and excite and animate your body
in the third part of our itinerary is going to be a bunch of additional topics and to be frank
these are just topics that I really like and I can't help myself so I'm going to tell you about
them there are topics that usually reach a little bit farther beyond the scope of a traditional
introduction to Neuroscience Course and there are things like Neuroscience of behavior not
only human behavior but behavior of diverse animal including vertebrate and invertebrate
insect species we're going to be talking about topics like mental health and addiction and how
these impact our sense of self and how that ties together with society and community and um and
other and and the legal system and then we're also going to be going towards connections between
neuroscience and Technology by looking at things like neuroscience and artificial intelligence the
history of how these fields have evolved together into doing things like um the different different
artificial neural networks that are like that are able to generate speech and generate images that
all of you have seen all over the Internet and we're also going to be talking about topics for
example like bring computer interfacing how it is that we can build machines that interact with
our brains both for rehabilitation augmentation as well as other applications and each of these
parts is going to be approximately 10-ish videos and the whole thing is supposed to be a quarter
long course at the University of Washington and so it's going to be approximately 30 hours worth of
videos broken up into small sections so my goals for you in this course are the following first
it is University level course on introduction neuroscience and so I hope that you will learn the
fundamental biological principles of Neuroscience I hope to give you enough intellectual scaffolding
so that you can hang knowledge that you learn later on onto the fundamentals of how neurons
work how neural systems work and so all of the additional topics will be added on top of that
fundamental layer of principles of Neuroscience next I want you to appreciate Neuroscience as a
living breathing field rather than having telling you how things are and this is just the way things
work you know I'm memorizing a bunch of terms and different Pathways Frankly Speaking I can't
memorize them either so I don't really want you to what I would rather you come away from the course
with is an appreciation of when we discovered something in Neuroscience what was the state
of the field at the time what were the leading ideas on hypotheses of how that particular thing
worked what were the Technologies and so what was the process of discovery of finding that thing out
as well as who were the very human scientists with our very human floss who discovered those things
a corollary of that is that one of my favorite things to do as a neuroscientist is thinking about
future Technologies this is actually what I do in my research life I think about not only what
can we do right now but what is inevitably going to be possible in the next 5 10 30 years and to
appreciate that Neuroscience is going to grow by Leaps and Bounds over that time framing waste
that perhaps none of us can really appreciate and anticipate but we can kind of think about it
and think about okay so if we can record not only from one single neuron at a time but hundreds
of thousands of them what will we do with all of that data right what can we do if we don't
only are able to monitor animal behavior in a single animal in a single lab in a small box but
we can actually see what it does out in the wild world and so appreciating neuroscience and the
process of discovery as well as the people who are players is one of the things that is my goal
for you and hopefully that's something you'll see throughout the course in all of the topics we'll
cover third thing that I have a goal for you is to be able to connect Neuroscience with health
and Society is an organ just like every other organ in your body and so just like every other
organ in your body if this is a course on the liver or the kidney we would most certainly talk
about pathologies and diseases of the liver and the kidneys so just like that we're also going
to be talking about neurological disease but those other diseases the brain is in a way that is
not true of deliver tied to my sense of self and identity and so when there are things that change
with my brain that very much changes my connection not only with myself but with the way that I
interact with people around me with my community and my relationship with my community and with my
with my local environment and so thinking about the implications of that is one of my goals in
throughout the course and I hope to especially highlight this in the context of mental illness
and drug addiction because throughout the last couple of decades our growing appreciation for
the fundamental biological basis of mental of mental illness as well as drug addiction has very
much changed the discourse of how people relate to themselves as well as relate to their loved ones
and other people around them it is social as well as legal sense at the same time I recognize that
hopefully I will inspire some of you to become career research scientists in Neuroscience but I
recognize that that's probably not the case for the majority of you who might find yourself
watching these videos and so if this is the last course on Neuroscience that you take in your
life well you're about to be bombarded with for the rest of your life is a bunch of news coming
out claiming to be the latest and the greatest advances in Neuroscience especially neuroscience
and health you're going to see articles claiming things now some of these are going to be
genuine advances really exciting things that are inevitably going to come out in the next several
decades but some of them are going to be BS so I want you to learn enough about the fundamental
biological principles of Neuroscience so that you can call BS when you see it for the rest of your
life Okay so our first lesson starts right now um you all know that you can see with your
eyes right okay so but your eyes you kind of sometimes people think of it as a camera so
you can kind of you know take a picture with your camera you can take a picture of your
eyes it kind of is the same thing right well you might know that it is in fact not so what
you see with your eyes is not at all what it is in reality in other words what you think you
see is oftentimes not at all what is in the physical reality because you don't actually
see with your eyes you see with your brain it is nowhere easier to demonstrate this than with
visual Illusions and so I when I'm not teaching this course I'm actually constantly on the lookout
for really cool visual Illusions I save them it's like I gotta show my students about this later so
I'm going to show you a couple of my favorite ones right now demonstrating this this observation
that we don't see with our eyes our eyes are not cameras and we see with our brains instead
okay so the first one is a really simple one there's two yellow dots on the screen I'm going
to ask you the question which one appears larger hopefully what you can tell for yourself is that
the one on the right that's surrounded by the relatively smaller purple circles appears larger
it will not surprise you because I've already told you this is a visual illusion that those
two circles are in fact exactly the same size because they're surrounded by larger circles
they're surrounded by smaller circles there's a relative perception that one of them is larger
than the other one even though it is not at all what is happening in reality your brain is lying
to you but it's lying to you for a good reason the second one this one is a kind of a recent one
that I saw in social media and it kind of totally broke my brain at the time I sent it to all my
friends and broke their brains and they're kind of mad at me one of them was actually mad at me
because it made them kind of nauseous okay so in this grid of dots what you're seeing is that
there's two different sides of this picture you'll see a bunch of intersecting gray lines and
there's black dots on the left side as well as the right side of this image what you'll see is that
there's a bunch of black dots that you can see on the right side of the image and they stay there
right I'm telling you I'm just going to tell you have to believe me now the left side has exactly
the same number of black dots as the right side but when you look at them and you look away
they disappear it is almost impossible for me hopefully this works on your screen even
if it's a small phone screen you can see that the black dots disappear when I look at
it so I'm looking right now I'm looking at up here I can see a couple of black dots
the ones down here have gone away once I look down I can kind of see the ones down
here I can't see the ones up there anymore these dots disappear on you but they don't
disappear on the right hand side if you don't believe me I'm going to zoom in on the right hand
side here's the gray grid with the black dots and over here is the same gray grid with the black
dots as you'll see the only difference here is that the black dots on the left side of the screen
are at the intersections of those great grids under the right-handed side of the screen they
are not and so that's kind of a clue of why it is that one side of the dots disappear you can't
even see them if you look away a little bit on the right hand side they stay put and you can kind
of see how many there are in this grid now visual Illusions are cool for two reasons one is that
humans are extraordinarily visual creatures and so demonstrating that you see with your brain and not
with your eyes is really easy to do and kind of fun and Charming to do when you do it with visual
Illusions but of course these Illusions are not um uh it's nothing intrinsically visual about the
fact that you can hack your brain by tricking it to think that something is there that it's not
and so if we were in a haptic Universe I can show you the following illusion but right now you
just have to take my word for it there's these illusions that exist in other sensory modalities
besides visual ones so here's uh one example of what's called a somatosensory or tactile illusion
so it works the following way if you um take your arm okay you take your forearm region and what you
can do is take something like a real little robot arm or something and then tap in Rapid succession
one spot tap tap tap tap tap and then I'm going to do the same thing by tapping at a second spot
tap tap tap tap tap tap okay that's it I'm going to tap one place location a and a different
place location B now the purse intercept the perception of what's Happening Here is not a
series of tops at a and a series tops at B the percept is going to be a series of taps that walk
from location a to location B in Rapid succession as if there were a small rabbit that is running
on your arm that is why this is called a cutaneous rabbit illusion now the salute salute pretty
robust but it does vary depending on exactly what locations you tap for example this works
on a patch of skin like euphora but it does not work on your fingertips because you actually
have a ton of touch receptors on your on your fingertips you can actually resolve that there's
two locations that are being tapped okay probably works on your calf on your leg too and you have to
be able to tap at the right frequency and with the right latency between location a and location
B otherwise to cutaneous rapid illusion breaks for them I can talk about this forever and I'd
be tempted to but we're not going to right now because this is just lesson a and I hope I
convince you with a couple of examples that we don't in fact see with our eyes we see with
our brains and our brains are built in such a way to represent information from the external world
not to just represent them I am not a camera I'm not interested in the reality what I'm actually
seeing right now I'm interested in looking at the aspects of the visual scene and the sensory
tactile physically seeing the auditory scene all of these different scenes in such a way that's
relevant for me as as a person and as a living thing to survive in the world okay that's why
we see with our brains and not with our eyes so to go on this adventure with me like I said
this is a university level course and so I will assume some basic familiarity with a couple
of topics now if these are things that you are totally familiar with that's awesome if you're not
familiar with every single one these topics it's actually totally okay you can come with me anyway
and if it inspires you to go back and review some of these topics that's something that you can
very much do in the middle of the series of videos and so because you Neuroscience is such an
interdisciplinary field we're going to be drawing a little bit of Concepts from a lot of different
fields and so here's a list of the things that I will assume that you have heard of and have some
familiarity with okay in the realm of biology I will assume that you know about the parts of an
animal cell that you eukaryotic cell that it has a nucleus where the genome the DNA lives that is
surrounded by a lipid membrane that is hydrophobic and separates the internal environment of the
cell from the external environment of the cell I will assume that you have heard about the fact
that there are proteins in in these cells that are expressed from The genome and that these proteins
are molecular machines that do all the work the really cool work that we do in all of these animal
cells because after all in order to understand the neuron we have to understand neurons as a cell
as a cell of your body just like every other cell because I already talked about how neurons are
electrical cells we're going to be drawing on a little bit of basic terminology and Concepts
from electricity and magnetism from physics so relatively basic things like what is a current
what is a conductance what is Ohm's Law things of that nature the mathematical prereqs are not
too rigorous I don't expect you to actually know calculus or differential equations but I am
going to use some notations from calculus and differential equations so for example if you see
something like the following DX DT equals f of x you should probably have heard of this concept
at some point where dxt means the derivative of x with respect to T and oftentimes I'm going
to be using t as a proxy for time so this is a Time derivative of x okay I don't expect you
to be able to solve these equations but I will be using this as a representation of ideas to
connect them with electricity and magnetism as well as to proteins as molecular machines and of
course the basic communication of neurons involves not only electricity but also organic molecules
and so I'll be assuming some basic knowledge of chemistry and organic molecules so for example
there's ions like sodium and potassium are ions they are electrically charged and aqueously
soluble and a lot of organic molecules that are that are going to be important players and
many of the things that neurons are going to do Okay so here's the itinerary if you choose
to go on this adventure with me I hope to see you for the next series of videos I'm really
excited to get started I hope to see you and uh because I'm a professor and I'm a pedantic
neuroscientist I will have to say that I hope to see you is something that people say on
YouTube but I fully recognize that you might see me but I'm not actually going to see you but
I am excited to make the next series of videos and I hope that you find them as interesting as
I have found the exercise of teaching them thanks