Kind: captions
Language: en
I think someday when we read the book of
uh of life when we read the book of uh
uh how a human body works uh and let's
say there'll be a chapter to the heart
and a chapter to the skin and a chapter
to your bones I think the chapter about
the brain will not only be the biggest
chapter uh uh uh in that book but it
will have cross references to every
other chapter in that particular book so
I think another way to say it is the
brain is as huge a mystery as humans
are in the sense that our brains are
involved in so many different parts of
our bodies Beyond just the idea of how
we think and how we make memories and
how we make decisions but literally the
kind of intimate relationship between
the rest of our body things from like
our kidneys to our spleen to our
intestines are all fundamentally related
to the nervous system so to really
understand the brain you would have had
to understand as much about the rest of
the parts of the body as well which is I
think part of what makes the brain so
mysterious so I think what what's
remarkable about brains is first all of
the things that they can do but how
similar some brains look to other brains
that can't do the same things so one of
the things we work on is what are the
differences between a mouse brain and a
human brain is there something obvious
in the brain that could lead us to say
this uh brain obviously produces the
monolisa and this brain just is
interested in cheese all day uh uh and
when you look microscopically at these
at a human neuron or a mouse neuron you
can't tell the difference at all uh uh
and I think that's what's amazing about
this idea that the brain is just
hamburger not only is it hamburger very
similar hamburgers are found in animals
uh uh that can't achieve the things that
human brains can achieve so something
just not about the meat itself but in
the specific organization of the
hamburger that I think gives human
brains this remarkable capacities so one
of the ways I I like to think about
brains and one of the ways I like to
talk about brains is that I think
neurons which are the cells that uh uh
uh uh live in a brain they're very
similar to the single- celled organisms
that live in a pond uh uh so they're all
these little single cell parium uh uh uh
eoli and I don't think any particular
neuron is any smarter than a parium or
an eoli or any of these other single-
cell organisms it's just that they live
in the weirdest pond in the world uh uh
probably in the universe for two reason
reasons one they are so packed with
other cells uh uh uh other eoli and
other parium that's the first and then
the second all of those cells are
apparently are trying to achieve the
same goal because if they all don't
succeed then the animal dies and then
Evolution uh uh uh uh uh uh gets rid of
it so I think to actually live in a
brain is not any more mysterious than it
is to live as a single- cell organism
inside uh uh a pond at the level of an
individual neuron but then something
magical happens in the collective action
uh uh of it so imagine what it's like to
be a single cell in a brain uh a single
neuron in a brain you're completely in
the dark uh you don't sense touch you
don't sense sound you live in a pool of
liquid uh that's about 98 uh uh uh
probably a little less than body
temperature say 98 or
97° and the only thing you're aware of
are the connections you have with other
neurons and the connections you receive
from other neurons and when you receive
this information from another neuron you
don't know whether it's visual
information or auditory information when
you send out this information you don't
know whether you've made a decision or
you've decided to wait uh uh uh whether
the human has uh uh decided to wait so
it's very much like each of these are
sort of independent units and they live
in the dark uh without any knowledge of
the world around them but evolution and
perhaps development have designed that
network uh uh to to give meaning to us
the basic principle that we think about
uh neurons uh is that we want to we want
to excite them uh uh and by that I mean
a neuron is almost an electrical
signaling unit most of the time it sits
quietly uh uh and then every every now
and then it fires a single electrical
signal which we call uh uh an action
potential and if we ask what is it that
can make one neuron fire an electrical
Spike and not another neuron fire
electrical Spike it's because it's
receiving information via its
connections from other neurons and so
when those other neurons decide to fire
Spike guard action potential they make
our neuron fire a spike or an action
potential and that propagates the
information that starts with our eyes so
there are cells in our eyes that fire an
action potential when they see a spot of
light versus not uh a spot of light you
could collect many neurons that see
different spots of Lights in different
parts of our visual world and wire them
together so that we take those spots of
lights and make a bar of light then you
could take all the neurons that respond
to bars of lights wire them together so
now that we respond to a rectangle of uh
uh light and if you take enough neurons
that respond to you know different
shapes of lights then you'll get neurons
that respond to faces which is just a
collection of those shapes put together
and the idea about brains is that from
the very external sensory systems all
the way out to our uh uh uh prefrontal
cortex that makes decisions there are a
series of abstractions where the neurons
at some lower layer that are looking at
spots of light group together via their
connections to make lines and they group
together to make shapes which then group
together to make
faces I think almost at the very first
moment we are transforming reality into
uh uh a as something we can use so if we
think about how many sensors we have on
our body so as I was saying in your
retina there are these neurons that
respond to light in each eye there's
probably millions of those uh uh uh
neurons and we have millions of neurons
that respond to touch and temperature
that uh uh uh uh across our skin we have
probably another million that listen to
sound on in in each year if we paid
attention to each little bit of
information from each one of those
sensors we would become so overwhelmed
that we wouldn't be able to make
decisions uh uh uh uh or actions which
is what we need to survive so at the
very first layer in including deciding
am I going to listen to something versus
look at something uh uh are are
decisions that brains make that already
start throwing away the vast amount of
information that our sensors have
collected about the world if your eyes
are open you're receiving photons from
throughout the visual field even if
you're not paying try trying to listen
you're receiving sounds uh uh uh uh and
even if you're not you know actively
touching things things my clothes are
actively touching my body at any
particular moment in time and the one of
the very first things any brain has to
do is to decide which of those millions
of streams of information is the piece
of information that the brain is going
to use to make predictions and coding so
often even though I'm uh uh for example
often even though as I move around my
clothes touch my body in a hundred
different ways maybe a thousand
different ways one of the first things
that my brain has to do is not pay
attention to the clothes on my body uh
and just like it does not pay attention
to the clothes on my body to have that
interfere with any decision that it's
going to make it also will not pay
attention to 99% of the visual stimuli
or if I'm paying attention to something
with my eyes I'm less likely to feel the
taste in my mouth or to hear sounds from
out in the street and so I think the
fundamental part of a brain is to
actually decide about which of those
millions of streams of information is
the most relevant to that body at that
particular moment in time and most
relevant for our survival right and I
think the reason brains have to do that
is that to survive we have to make
predictions and we have to make
decisions fast if we had to comb through
if the brain had to individually comb
through those millions of pieces of
information and decide which of them was
important before it made a prediction or
before it made a decision we wouldn't
have survived uh and so even before
predictions are made and decisions are
made the brain has to Cull and
immediately decide which of those pieces
of information which very small fraction
of all of those pieces of information
actually gets to be processed by the
brain I would say the reason we have
brains the reason brains have have
evolved is to deal with the overwhelming
information of reality and try to figure
out a way to filter it as soon as
possible to make a pred addiction to
make a decision I think a one way to
think about why brains throw away so
much information is that in in there are
moments in our lives perhaps there used
to be more of these moments in earlier
days there are moments in our lives
where making a decision is life or death
uh uh uh there's a tiger coming there's
a food source uh uh uh uh uh coming and
in those moments you don't have time to
analyze the billions of pieces of
information that are coming in you have
to decide one way or the other I think
those are the moments that have driven
Evolution to make us mostly sparse
Samplers of the world or sparse Samplers
of all of the sensory information that
we receive and it's a fundamental part
of our survival it's not an artifact
perhaps of humans or or Etc it probably
exists in the very earliest nervous
systems which is the the very earliest
nervous systems probably have to solve
the information this problem of there's
so much potential information to receive
about the world which is actionable and
which is
not I think one way uh to think about a
brain is is what is a brain uh why could
I not have all of the photo uh the
retinol photo receptors that sense light
in my eyes just directly connected to my
muscles uh so that every stimulus winds
up in a motor action and in fact I think
the definition of a brain is something
that sits between our sensors and our
motor actuators and actually decides
which information to throw away and in
fact that might be the purpose for why
we've evolved brains in the first place
yeah so and one way to sort of think
about how brains filter information is
that at the very earliest stages in our
eyes uh uh uh for example we have all of
these particular sensors that detect
light but those sensors don't
immediately uh uh send that particular
information into our brains and into our
cortexes in the retina itself they
interact with each other and they
compete with each other so the sensor
that sees light here and uh might
compete with the sensor that sees light
you know to at a different part of our
visual field and and wind up competing
with each other or voting for each other
with which one piece of that information
winds up being sent to our our nervous
system in fact another way to say it is
that in our eyes itself there's a part
of our eye that is very has a very high
density of these sensors called phobia
uh and information that lands on those
particular sensors has a higher uh
competitive ability than information
that votes on the periphery of uh of our
eyes and so information from the inside
of our phobia is much more likely to be
sent into to our uh uh uh cortex than
the equivalent information that comes
from the periphery that's right so so in
fact in all of our sense organs uh there
is probably competition at the very
earliest stages of detecting some
sensory stimuli uh that's fundamentally
related to our abil to our ability to
make uh uh uh uh decisions so for
example in our auditory system we
probably want to pay attention more to
loud sounds that are closer to us than
sounds that sound distant and so even at
the level of our ears processing this
auditory information we will the sounds
that come from closer to us or appear to
come from closer to us have a
competitive AB of an increased
competitive advantage to get that
information into our brains versus
sounds that come from far away and one
one way to think about this is that we
can we can try to imagine how much
information uh uh is thrown away at any
particular uh uh stage of the nervous
system so at our eyes at our sensory
systems we're probably receiving
millions of pieces of information per
second right and and in each stage uh
that information becomes abstracted and
sampled out until you finally get to
perhaps uh uh how many pieces of
information a brain can keep at One
Moment In Time this is called short-term
uh uh memory and it turns out that after
lots of psychological and cognitive
studies in humans humans can keep track
of something like seven pieces of
information maybe seven plus or minus
two pieces of information at any one
particular moment in time and those
seven piece that seven facts for example
I think this is one of the reasons our
telephone numbers are seven to nine
digits uh uh because we did a lot of
work and how many numbers could you keep
track of and now actually psychologists
think that the number might even be less
it might be five it might be three
pieces of information so we go from
millions and millions of pieces of
information at at our eyes and that
information becomes so sparse and so
abstracted that it's finally associated
with three things to five things at any
one particular moment at the highest
levels of our
processing I think a great question a
great retort is that if I'm just keeping
track of 1% of the information in the
world how can I uh drive a car uh uh uh
and it turns out that first 1% of of the
information that comes in from the world
is actually an enormous amount of
information in fact it takes a brain
probably of this size to deal with 1% of
the uh information and it's also because
specifically when I'm driving I'm not
only using that 1% of that information
but I'm using the memory of what the
where the cars were 5 seconds ago the
memory of where the pedestrians were 10
seconds ago and I'm actually predicting
at the same time I'm taking sensory
information where will those pedestrians
be 5 seconds from now where will the
cars be 10 seconds from now and in fact
to do both those predictions and those
decisions it would be impossible to
collect the information and in fact
driving a car I think is a remark ably
good analogy for why we can only
sparsely sample the world because if we
had to actually pay attention to
everything on the road at the at one
particular time and and we know how long
it takes approximately the brain to
process information it would take
minutes maybe even longer before I
decide to push the accelerator down or
to push the brake or to turn the wheel
right or to turn the wheel
left I think the idea that brains are
are storytelling machines narrative
machines is something that really just
recently starting to uh uh emerge in
Neuroscience but when you think about it
uh it's not surprising because literally
everything else brains do is about
telling stories uh uh not just the
people who write stories and make movies
and make music and make art but our
legal systems are about telling stories
our political systems are about telling
stories our Educational Systems are
about telling stories so if we looked at
all the ways that we've used brains uh
uh n some vast majority of the
applications of brains philosophy uh uh
uh uh even our understandings of the
universe are really narratives where we
we often use analogies and story devices
so the fact that you know brains
themselves use the narrative to guide
the world it becomes less surprising
when we think about how many other ways
we use our brains which is almost always
to tell stories and you may say well
what does uh uh what does fudging with
reality have to do with making decisions
and I think it it's because you have to
make predictions fast uh and actually
when you think about all the other ways
where we make predictions what a
prediction is is it's taking as much of
the information in the world as possible
compressing it uh uh excluding the
things that are irrelevant to a
prediction so that you can make a
decision fast a prediction is really a
kind of a shortcut tool where you take a
whole bunch of information cut out the
parts that are irrelevant you hope uh so
that you can make a fast prediction so
you can make a fast decision the vast
majority of the brain's job is to say
what is going to happen in the next few
seconds and in fact in in really uh uh
species with larger brains that we
associate with intelligence all that
happens is that that ability to predict
forward in time just extends and extends
and extends so so maybe what a mouse
does uh uh what a mouse brain does is
actually predict what's going to happen
in the next 5 seconds or the next 10
seconds but maybe there are some animals
that make tools that like birds or or or
or or primates non-human primates that
can then make that prediction out to uh
minutes or days or weeks and what's
amazing about human brains is that we
try to make predictions out to years and
decades uh uh and it might be that that
our ability to make predictions over
much longer time scales is fundamentally
related to our ability to make
narratives which is fundamentally
related to our ability to sort of parse
out this huge information World well
sometimes when I think about brains I
get scared and it's not uh uh and I get
scared for a bunch of reasons I think
two of them uh uh that I would list is
that I'd like to believe that I am in
charge of my life that I am the agent of
my life that I actually uh uh can
control uh uh uh uh uh my emotions my
abilities my desires Etc and the more I
learn about brains the more I realize
that I probably the idea of a Bobby
casturi inside my skull being in control
of all of these things is probably not
true uh and I think it's that lack of
control uh uh uh uh uh about my own uh
uh uh abilities or my ability to control
my body I think is is is one of the uh
scariest things I think the second thing
I think that sometimes scares me uh uh
is that what what's left of me uh is
there actually a concept of me left
after I'm done learning everything
inside how every part of a a brain works
and in fact it's probably not you you
perhaps it's probably true that if you
could
collect make neurons in a dish uh uh uh
or uh and connect them together in a way
uh uh just based purely on uh uh physics
and chemistry and Etc that that dish
Bobby casturi uh uh would have me would
be me my personality Etc and and the
idea that I'm not unique and that I'm
not in control of the two things that
sometimes wor worries me when I learn
too much about
Neuroscience I'm not sure if we're close
to solving the problem of Consciousness
I think part of the issue is that we
really need a much stricter definition
of it uh uh we need to know when we say
Consciousness are we talking about being
conscious of our internal states are we
talking about about being conscious of
ourselves introspection versus being
conscious of the world uh uh uh outside
being conscious of different people or
different decisions versus uh uh uh
internal Consciousness and it's might be
possible that those are two different
kinds of of Consciousness with
mechanisms that are fundamentally uh uh
uh different second I think if you know
if you watch the world around us uh
there are algorithms now that are
performing uh that are able to do things
that we thought algorithms wouldn't be
able to do beat us in chess beat us in
poker which always bothers me because
that involves deception uh uh beat us
and go are those algorithms feeling a
sense of Consciousness when they achieve
those uh uh uh uh decisions is
consciousness a thing that's actually
made of biological matter uh uh or can
Consciousness be created in silico if
you will and I think once we get to a
better definition of what Consciousness
means and I a second thing is we
probably once we have that better
definition we need to know whether
Consciousness is something that's
Universal across all animals that have
brains uh uh or is it something that's
only emerged in humans or non-human
primates or uh uh Etc and I think once
we get to better definitions and answers
for that then we'll be able to come up
with experiments that actually tease or
tease out the actual mechanisms of
consciousness
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