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From YouTube: Michael Berry - Interview with a Neuroscientist
Description
Matt talks to retina specialist Dr. Michael Berry, of the Princeton Neuroscience Institute. They discuss the optic nerve and the path its signal takes, how ideas are represented in neurons, and the complexity of light itself.
A
B
I
mean
I,
guess
it
probably
started
with
the
philosophy
of
mind
class
I
took
bath
in
college,
and
you
know
it's
basically
like
my
favorite
class
in
college,
and
you
know
they're
just
these.
These
very
profound
questions
about
you
know
mental
phenomena
which
which
seem
potentially
disembody,
not
physical,
and
yet
it
just
seems
like
they
obviously
have
to
arise
and
in
the
brain,
and
so
the
the
fact
that
there's
this
connection
between
the
mind
in
the
body
I
just
I
just
found
fascinating.
B
B
A
Let
me
introduce
you
to
our
audience
thanks
for
watching
interview
with
the
neuroscientist
I'm
Matt
Taylor
from
dementia,
and
we
have
in
our
offices
here,
dr.
Michael,
berry
from
Princeton
he's
a
researcher
and
a
professor
at
the
Princeton
Neuroscience
Institute,
so
happy
to
have
you
here
today
thanks
for
joining
me
and
for
your
time
and
we're
going
to
do
interview
with
a
neuroscientist
and
I.
Don't
know
you,
you
don't
know
what
I'm
about
to
do,
but
this.
A
The
neurosciences
I
have
four
topics
in
this
and
their
neuroscience
topics
and
we're
gonna
go
through
these
and
you
get
to
pick
which
you
know
what
to
talk
about.
So
we'll
just
kind
of
go
through
the
different
topics
and
I'll
show
them
off
to
you.
Look
at
the
first
one
see
the
blank
like
City
of
Light
deal
for
the
birth
of
ideas,
so
this
is
going
to
be
the
deep
one.
There's
a
thought
experiment
and
this
one
nice
and.
A
A
A
A
I
mean
this
is
a
huge
there's,
a
lot
of
information
coming
into
this
turn,
I
mean
if
you
cut
the
optic
nerve
and
I
mean
and
then
freeze
time.
We
are
gonna,
see
like
lots
of
nerve
activations
coming
out
electrical
pulses.
So
my
what
I'm
really
curious
about
is:
where
does
the
optic
nerve
go
like
what
parts
of
the
brain
does
it
get
routed
through?
A
B
The
optic
nerve
goes
to
two
primary
places
in
the
brain.
It
connects
to
the
the
thalamus
okay,
so
the
thalamus
is
the
sensory
gateway
to
the
brain,
so
in
particular
the
visual
part
of
the
thalamus
and
then
where's
the
thalamus
on
there
there'll
be
these
footballs
these
footballs.
Okay,
this
is
an
old
brain
so
and
from
the
thalamus.
Then
it
goes
straight
up
into
the
primary
visual
cortex,
which
would
be
you
know,
kind
of
the
back
of
the
brain.
B
A
B
B
The
context
or
something
we
don't
know,
we
don't
know
that.
Well
so
the
feedback,
it
seems
like
it's
numerically
ten
times
stronger
than
the
feed-forward
right.
And
yet,
if
you
look
at
what
patterns
of
light
caused
that
Fleming
cell
to
fire,
it
seems
have
a
receptive
field.
That's
essentially
identical
to
the
input
optic
nerve
fiber.
So
it
seems
like
all
that
feedback
did
nothing.
B
So
why
is
it
there?
How
could
that
be
yeah
and
there
there
is
some
evidence
that
what
that
feedback
does?
Is
it
modulates?
The
gain
of
the
neuron
a
little
bit
makes
the
activity
a
little
bit
stronger.
Maybe
if
you're
expecting
that
that
visual
pattern
right,
but
it
seems
it
seems,
like
a
surprisingly
weak
effect-
isn't
all
all
the
circuitry.
B
A
B
A
B
Retina,
that's
that's
a
little
different,
so
the
retina
gets
relatively
little
feedback.
Okay,
okay,
it's
maybe
five
percent
of
all
the
fibers.
Do
we
know
why
that
even
exists?
Yeah.
We
have
some
idea,
one
of
the
feedbacks
okay,
so
the
the
optic
nerve
branches
to
two
main
brain
areas.
I
said
the
thalamus.
The
other
is
a
called
the
superior
colliculus
okay,
but
it
also
branches
to
several,
maybe
ten
other
minor
brain
centers.
One
of
the
minor
brain
centers
is
called
the
pre
techno
nucleus.
Okay,
what
that
does?
Is
it
controls
your
pupillary
light
reflex?
B
B
So
if
you
shine
a
really
bright
light,
your
pupil
contracts,
okay
and
then
that
reduces
the
light
intensity
on
your
on
your
retina,
so
it
kind
of
helps
stabilize
the
amount
of
light
falling
on
your
retina
right
when
it
gets
dark.
It
opens
again
right
so
the
this
little
pre
tectal
nucleus
makes
the
decisions
to
dilate
or
contract
your
your
pupil,
and
so
so
that
you
know
that's
encoded
in
motor
neurons
that
go
to
you
I'm
my
muscles.
That's.
A
B
There
there
are
other
influences
on
your
pupil
diaper,
it's
kind
of
a
sexual
attraction,
arousal
arousal
a
whole
whole
other
set
of
circuits
that
are
not
purely
related
to
light,
but
so
one
of
the
things
that
protect
all
nucleus
does
is
it
also
feeds
back
to
the
retina
okay,
and
that
feedback
is
kind
of
a
modulatory
feedback.
So
the
idea
is
the
retina
needs
to
adapt
to
the
overall
light
level
right?
Okay,
because
if
you
have
thousand
photons
a
second,
you
need
to
have
one
type
of
response.
You
have
two
photons
a
second.
B
You
have
different
stronger
gain.
Let's
say
it's
very
okay,
so
the
pre
tectal
nucleus
is
about
to
change
the
light
intensity
when
your
retina
mm-hmm.
So
you
know
it's
going
to
change
so
the
pre
tectal
nucleus
has
a
feedback
that
helps
the
retina
kind
of
pre,
adapt
ahead
of
time.
To
give
a
knowledge
that
it's
about
to
change
the
light
level,
I
guess.
B
Kind
of
built-in
system-
so
that's
that's
one
example
of
a
feedback
to
the
retina,
the
other
one
that
is
kind
of
crazy
is
from
the
olfactory
bulb
really
so
this
has
been
seen
in
goldfish,
I'm,
not
sure
if
it's
true
in
human,
but
the
idea
is
in
goldfish.
If
you
smell
amino
acids
in
the
water,
okay
could
be
food
mm-hmm.
B
So
the
feedback
to
your
retina
causes
the
retinal
neurons
to
have
more
sensitivity
for
color
and
spatial
detail
less
for
for
temple,
information
interesting
and
if
the
food
goes
away,
then
maybe
you
want
to
be
prepared
for
predators
and
it
goes
back
to
Temple
sensitivity
that
makes
sense.
I
can
see
that
happening
and
other
species.
You
know,
there's
there's
there
a
couple.
These
modulations
of
the
retina,
but
they're
relatively
minor,
bring
in
the
skeletons
so
the.
A
A
B
A
But
we
don't
have,
but
it's
not
just
a
camera,
I
mean
when
you
go
to
grade
school.
They
teach
you
your
retinas
like
a
camera,
but
no
so
so
so
much
more
than
just
a
camera.
So
I
guess
we're.
How
does
the
retina
even
make
sense
of
all
those
photons?
What
are
the
basic
mechanisms
it
uses
to
encode
information
in
those
yeah.
B
A
A
B
By
a
factor
of
a
thousand-
and
you
hardly
notice
so
the
retina
has
to
adapt
tremendously
okay,
you
know
when
it's
really
dark
your
your
retina
needs
to
be
able
to
detect
individual
photons
mm-hmm,
which
is
which
is
kind
of
incredible.
Okay,
it's
really
good
at
it,
and
so
there's
a
it's
actually
very
well
known
how
biochemicals
and
photoreceptor
cells
do
that.
You
know
the
idea
is
the
photon
strikes
one
molecule
and
changes
its
shape?
B
Okay,
then,
that
molecule
moves
around
and
it
triggers
reactions
in
a
thousand
secondary
molecules
and
those
each
trigger
reactions
and
hundreds
of
within
retina
cells
within
each
receptor
cell.
So
the
one
photon
ends
up
changing.
You
know
the
activation
of
thousands
of
molecules
by
by
this
amplification
procedure.
So
so
you
know
that
that's
how
you
can
detect
individual
photons,
but
then
the
same
cell.
You
know
if
it's
getting.
B
A
A
B
B
Know
if
you
take
your
actual
video
camera
and
you
like
look
at
the
sky,
it's
all
washed
out,
yeah
right
right.
If
you
do
that
with
your
eye,
it
looks
fine
yeah
and
that's
because
your
your
video
camera
now
has
an
overall
game
control
for
the
entire
screen
right.
Okay,
but
your
your
retina
has
a
game
control
for
each
pixel
yeah
each
cell
everywhere,
you
have
has
its
own
game
control
that
changes
by
actually
much
more
than
the
video
camera
can
change
for
a
game.
So
you
know
the
retina
is
really
amazing.
A
B
A
B
B
B
It's
it's
much
lower
density,
so
you
get
kind
of
the
gist
of
the
image
in
the
periphery,
and
you
see
the
fine
details
in
the
center
and
then
you
move
your
eyes
to
new
locations
to
get
the
information
that
you
need
about
those
locations
and
then
your
brain
kind
of
stores
that
all
together
in
kind
of
details,
so
you
see
the
whole
world
at
high
resolution
right.
Even
the
moment-to-moment
you're
only
getting
high
resolution
from
a
tiny
little
piece
of
lab.
That's
interesting,
which
is
you
know,
but
our
brain
kind
of
pieces
everything
together
smoothly.
A
B
B
A
B
A
This
is
sort
of
a
very
topic.
That's
already
covered,
okay,
the
birth
of
ideas,
so
they
came
today.
So
this
is
a
let's
do
a
thought,
experiment
and-
and
so
let's
pretend
me
in
a
box,
a
black
box
with
a
hole
in
it.
You
can't
look
at
it,
but
you
just
look
at
it.
You
just
reach
in
and
you
feel
something
and
if
you
and
I'd
like
to
you
to
kind
of
maybe
go
over,
what's
happening
in
your
senses
and
in
your
brain.
As
this
happens,
you.
A
B
I
mean
it's
really
important
that
you
can
move
your
hand
around
absolutely
yeah.
You
know
so
so
so
kind
of
exercises
sometimes
do
with
my
students.
Is
you
don't
have
a
student
like
come
up
in
front
of
the
class
close
their
eyes?
You
can
hold
up
their
hand,
I'll,
put
an
object
on
their
fingers
right
like
a
peanut
or
something
I
have.
A
B
Asked
what
did
what?
What
is
it
no
idea
and
then
with
their
eyes
so
close?
They
say
you
know,
feel
it
right
right.
You
know.
So
your
sense
of
touch
is
is
a
very,
very
active
sense.
Yeah
and
you
know
roughly
the
way
we
think
things
go,
and
this
is,
you
know
closely
related
to
kind
of
work.
That
Numenta
does
is
that
you
know
your
brain
kind
of
every
moment.
It's
it's
making
a
prediction
of
what
you're
you're
going
to
feel
on
the
tips
of
your
fingers.
You
know
it
as
you
move
your
finger.
B
You
know
over
the
object,
so
you
you
take
in
the
sensory
data
in
the
first
moment
kind
of
activates,
some
representation
of
possible
objects
like
maybe,
if
ever
very
finger
a
whole
set
of
fur,
then
maybe
think
of
a
teddy
bear
sure,
and
so
that
feeds
back
a
prediction.
As
you
move
a
little
bit
more,
what
should
you
feel
if
it
were
a
teddy
bear?
Okay,
let's
say
it
isn't
exactly
like
that
right!
You
know,
then
it's
new
information,
you
update
the
pretty
ribbon
or
it
moves.
A
B
It's
like
this,
you
know,
like
one
other
thing
about
the
visual
system.
That
I
think
is
is
really
pretty
fascinating.
I
mean
you
know,
vision
works
so
well.
For
us,
we
just
look
at
a
face.
I
mean.
Oh,
we
know
who
that
person
is,
it
seems
effortless.
We
have
no
idea
of
like
what
the
neurons
are
doing,
but
there's
so
much
computation
going
on
underneath
the
hood
and
one
example
of
that
that
I,
like
is
the
fact
that
you
know
your
eyes
are
always
moving
mm-hmm.
Okay.
So
if
you
have,
if
you
consider.
B
B
Spatial
shifts
correct
for
your
your
eye,
movements,
you're,
always
bringing
the
same
information
together
in
the
right
place,
and
we
just
have
have
no
sense
that
are
even
moving
our
eyes
or
our
heads
or
again,
even
though
we
always
are
so.
We
kind
of
create
this,
this
kind
of
invariance
in
the
world,
even
though
it's
it's
not
very
closely
related
to
the
primary
sensory
cells
and
what
they're
doing
but
I
guess
it's
it's
our
model
of
the
world
that
we've
been
creating
for
years
and
years
and
years.
It
makes
sense.
A
To
us,
that's
why,
when
you're
babies,
none
of
our
actions
make
any
sense
at
all.
It
seems
like
they're,
just
random
you're,
just
bumping
into
things
looking
around,
but
over
time
you
learn
and
you
learn
and
you
learn
and
those
associations
start
coming
up
until
you
have
control
over
your
actions
and
you're
interacting
with
things
with
purpose.
Yeah
very
fascinating,
well,
dr.
berry
think
you've
been
taking
the
time
that
displeasure
with
me.
I
really
appreciate
it,
and
thanks
to
go
up
for
watching
interview.