So hello everyone.

My name is Andy Chung and
today doing a presentation about

the neural correlates of real
visual spatial attention.

So at any given moment our
visual system has come

from barred by stimuli
from all over the place.

It's like a fire hose of information.

So for example if I look at the Red Circle
here and I want to go to Starbucks.

I would have to select somehow
select the Starbucks and

suppress the Cinnabon or
the marble ice cream.

So how is our brain doing well
one way we can study this

despite looking at near
versus far stimuli.

So neurons in our visual system
are crossed each have their own receptive

field which is a portion of
the visual field and when two stimuli

are far away from enough from each other
they fall in separate receptive fields.

So there is no competition for
representation.

However when the two to stimuli
are right next to each other right here.

Like right here the stimuli from
the receptive field of a single neuron and

those two stimuli must compete
representation in the neuron.

So the study and the R.P.

we can look at the E.G. and present
a stimulus over and over and over again.

And then taking these chunks of data and
averaging over each other

we can we can eventually
the noise should average to

zero with enough trust with enough trials
and what comes out is the signal and

the signal looks like a looks like this
is in a way form that has positive and

negative deflections that
the negative is pointing up and

by convention and voltage versus time.

So the P.C.

is defined as the difference between
the contra lateral and real hemispheres.

So if you were to take an electrode and
look at both sides.

You would get a result
that looks like this and

if you of course subtract the red
line from the blue line you again.

Then look at sometime between between
two hundred three hundred milliseconds

eventually get to P.C.
which is right there.

And again negative is pointing up and
this is a vote versus time.

Also the P.C. is generally found in
the posterior section of the skull.

So Previous studies have shown
that the amplitude of the N.T.

P.C. correlates with the degree
of target selection.

So when you have a reduction and
then two P.C. I mean is that there's more

difficulty selecting a target and
you have degraded target selection but

this is true for all the visual
fields previous studies have

also when calculating the end to P.C.
have collapsed the upper and

lower visual fields over each
other when averaging out forms and

that brings us to our current
problem to P.C. behave

differently when attending to stimuli
in the upper and lower visual field.

So here is an example of
our experiment set up.

We have thirteen participants
each of them are Georgia Tech

undergrads and they are equipped with
a thirty two scout electrode cap.

And we also have facial electrodes
attached to their face to movement any any

trial that has significant amounts are
taken out because they affect your P.C.

So the participants look at a computer
screen over here which shows the task and

another separate computer monitors and
records so.

As an example of the layout of the scout
over their head and what we're interested

in what we're interested in are the ones
that are circling right here the P.Z.

are three and P's your floor which
are as opposed to electrodes

so here are two examples of what the
participant and I see a near condition and

the far condition and the near condition
the target which is the upside down.

T. here and the distractor are right next
to each other and in the far condition

the target and the distractor
are separated by two filler stimuli and

these these are divided
into four quadrants and

randomized and distributed evenly
evenly among the four quadrants and

some of the dependent measures were
looking for our accuracy response time and

T.P.C. waveform so
here are some of the behavioral

results we did not find any significant
difference and any of the conditions

on the lower left hand graph
here it is error rates on the Y.

axis and the four conditions on the X. and

on the lower right hand we have reaction
time and all the conditions on the right.

And we expected to see for

the near condition that there
will be greater error rate and

a greater response time than the far
condition because in the near condition

should be more difficult to determine
distinguish between the target and

the destructor So
here are some results for our data.

So this is again may get is pointing
up and that's the voltage and the X.

axis is the time and

it might be easier to see the results
from the bar graphs here on the bottom.

So the lower left bar graph has and
T.P.C. amplitude on the Y.

axis and the four conditions on the rights
and on the right hand graph shows the.

The amplitude on the Y.
axis and the conditions on the right.

So for the lower visual field the near
condition showed a great her P.C.

in the FAR FAR FAR condition.

However and
up her visual field the the N.T. P.C.

was almost nonexistent here and
greater and the far condition.

Furthermore we also noticed that there
was a pause of deflection after the entry

P C sometime after the N.T. P.C. and

the P.T.C.
was also there was greater positivity and

up are going dish and then in a lower
condition as you can see over here.

So in conclusion.

You cannot average over lower and
upper visual fields because the P.C.

behaves differently depending on
whether which visual field it is in and

there is also more to the N.P.C.

there simply correlating
it with target selection.

So some of the possible reasons
that this may be happening is that

depending on whether the stimulus
has an upper or lower visual field.

It may be activating different
parts of the brain and

another paper has noted that our lower
visual field has a higher resolution

of discrimination by
the upper visual field.

So some of the some of the future or
one of the reasons why we

probably did not have a significant
difference in our behavioral data

is because the target locations were
limited to the red circles here.

So eventually the participant may be
able to predict where the target and

decoys may be so future structure
studies we should randomized the target

location locations of the target and
of the equally thing that we.

Need to know is whether the competition
is needed to target the Detroit or both.

And you can study this by placing
the target on a centerline because

stimuli on the center line do not
elicit an end to P.C. response.

So I would like to thank Dr Paul
her boss my faculty mentor and.

My graduate mentor for
those experiment and

thank you thank you.

Plenty.

Now it's time for
me to present me with your

five minutes per question so
we can probably get so

if you really thanks.

When you randomize your
gift you know what we would

be very we're not sure because

this kind of this kind of result kind
of changes the way people see N.T. P.C.

because people always thought that it's
the same no matter where it where it's at.

But now like there's a there's a there's
a relationship between your P.C..

And how much you are discriminating.

And depending on the upper and
lower visual field so

basically a lot more research
needs to be done and

especially like an upper and
lower like what's going on.

I think one of the papers
described like the P.T.C.

may actually be part of the part of this
entire away form like P.T.C. might be

suppression of the distractor stimuli so

yeah you should maybe perhaps we
should divide this into two one name.

The negative paper described
as some of the negative and

the positive positive distractions.

So one way

that you can thank all of your it's
like to go back and explain why this is

why this is important and T.P.C. is
happens to be a really really easy thing.

A study that we've kind of thinking
with difference between contra lotto and

so lateral way for us when you're when
you see I mean you tend to a stimuli

sort of measure of measure for them

as a measure of how much how well you are
paying attention tending to something and

suppressing a distractor I

mean really you know

it's like if the.

If the stimulus on the right side
you would subtract left hand side

from the right hand side and
that's basically what I should be and

then you get into P.C.
and supposedly the more discrimination.

The more the bigger the anti P.C.
but it's all different now since upper

lower visual fields are different and
how many I

think a thousand fifty
fourth place thousand and

fifty two per hour per
hour per participant but

we don't want those three and yet.

So basically these these two these two
conditions across the four quadrants

like you think.

Well we're here we're

just going to get Yeah that

paper described I'm not really sure why
they thought it was more discriminatory.

But I thought that maybe maybe we
don't really any things don't really

come out as attack us from above
the curricular attack us from below so

maybe from the evolutionary standpoint
we might need to see things

on the ground more and more perceptive
Laden something from above.

You know I think it's here.

The other way and it's a little bit early

on in the media right away but

if something comes over you
know if you raise the right and

you're right it's really good.

Yeah I think that's right.

Thank you yeah yeah and that's just
something I just thought of I don't know

the paper didn't say that but that's my
explanation of possibly why it's happening

to me great.

You know like there are

acutely Thank you.

On the on your left hand I think yeah.

So generally in the back of the head.

You can see this and T.P.C.

play for him when you subtract
a country like the president.

I don't think he actually got monkeys.

I think he's had this response to so
they tested us and

now he's going to have some response.

I'm not sure if it's called into P.C.
but I'm going to go with it.

Here it is going to be OK But

anyway what about if it was
a auditory stimulus really you know

this is not sure about the tourist or
maybe somewhere in the auditory cortex.

You know like somewhere in
the sides of the temple of

I'm not sure about I don't know
much about this commentary and

you

know this didn't take as long as
I thought it would be OK We're

going to continue with the end.

So I mean to me that matter
that's exactly right.

You're getting to know the future work.

Yeah there's lots of things for
the gusto and

some of the technical well presented
which is really the way that

how you go about maturity how the target.

I guess you can put on the center line
because it's depending on because

this peculiar sore spot because it's
Armada left or right which is which is

why you can see the contre lot on that's a
lot of so I guess that's on a summer line.

I'm not sure why why there is no and
neither is ninety three she response

because the letter was.

I think it's in the brain and
I think they show it.

I don't think it's a good many years.

Yet you want to see how they response.

Yeah.

I have a question for tonight.

And then you can see the end
user who says yes you

did you describe how you got to know yeah.

Previous results.

Research has shown that if you look
at that look at these two way forms

likely to see this and to P.C. happening
and I think you first saw it in one piece

and just want to see if it was in humans
and I saw in humans as well so they say

they use that as a lot
further with that and yet

most previous studies thought of it as the
same in all of the whole of fields of or

all fields of visual field so
now we know that you kind of have to

be careful about what quadrant of
the of the of the visual field

you're looking at when you look at
into P.C. and then your P.C. for

problem are part of the is divided into
a positivity and negativity component.

You know pulling on your plate.

It's not a problem.

I think it's that although my ear.

What's the connection in this case.

It was the way it is in
the nature of it and

it's yes I mean just think about it.

You know that you know we pretty
much go on just the N.P.C.

when we look at attention so
behavioral as well but

past history to make
sure they are on task so

mainly mainly is that your
pee data that we look at just

like you know I

was I was really just friends
thinking that I'm not going

to get what you know I
was just wondering how

did you meet its stance
you did it then Michel

it's an issue of like
how correlates like you.

So I generally like in the past like
people thought that a bigger and

T.P.C. meant that you're discriminating
things much better than a Smart.

So like fifty you would
expect a smaller into P.C.

in this condition than in this condition.

So I guess in the lower end and
in this craft it was true for

the upper visual field but
not true for a lower visual field.

So there's something else going on

between just just just
a magnitude twenty P.C.

and I

think yeah like you know
something that's coming at you and

the great big empty P.C. Yeah so that
means you're discriminating really well so

you have the L'Oreal we
said we expected like.

Greater error rates and response times for
the near conditions ten the far conditions

that was were these studies
have naive stuff like me and

then air traffic control right and
see because really it doesn't matter.

Well because you've got you know obviously
the ability to discriminate between a lot

of material that's green I
would be I think when you

go in there with people who have
actually been trained to do that

I would say here he's free

to have entropy Seaway formula for
small differences and stimuli.

But I bet you would think that he used to
think you know very crowded field distinct

Yeah yeah hopefully like that in
the future one bad thing about your

peace studies is that you really don't
know where things are going on the brain.

So like I said possible
things that they're active in

different areas of the brain.

So maybe something like an M.R.I.

study would be able to so that we can
maybe look at different electrodes rather

when it's in the lower part of the upper
field and maybe to see the more those two

like you know right now we're just looking
at those two electrodes you default.

We get data from all of them but so

far we're not using the most we
could we could but right now.

I guess we still have to
know which ones you know so

that if we were just very rational.

I guess we will.