オブジェクト表象に関わる脳活動は遮蔽時間に伴って変化するか(第23回大会 優秀発表賞抄録)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

The

foPanese

fournat

of

Ps.vchonotnic

Science

20e5,

VoL

24,

No,

1,109-1IO

Summary

ofAwarded

PresentationIP03

Effects

of

object

occlusion

on

brain

activity

for

representation

of

a

dynamic

scene

Toshihide

IMARuoKA*,

Jun

SAIKI**,

and

Satoru

MIyAucHI***

Kdnaaawa

institute

of

Technotagy*,

JST

RI?ESTO;

K.voto

Ubeiversdy**,

AJdetional

inslilute

of

Communications

and

Technologyr***

In

a

_previous

study we

have

shown,

by

using

functional

MRI

during

a

multiple

object

permanence

tracking

(MOPT)

task,

that

the

representation of

dynamic

objects

needs

the

coopera-tion

of widespread neural systems

(Imaruoka,

Saiki,

Miyauchi;

_2005).

_In

_the

_present

study we modified

the

MOPT

ta$k,

and

measured

the

brain

activity

during

the

task

with

fMRI,

so

that

we

could explore

_thc

_precise

correspondencc

of

a number of cognitive

_processes

and

neural

systems

related

to

the

representation

of

dynamic

objects,

The

cognitive

_processes

included

ebject

tracking,

the

maintenance

of visual

information,

the

integration

of

visual spatial

inforrnation,

and other

information

about an object.

The

neural

systems

included

the

anterior, superior,

and

inferior

frontal

areas,

and

the

parietal

area,

The

resuits suggested a close re}ationship

bctween:

(a>

_the

right

superior

frontal

_gyrus

and

the

maintenance oi a

coherency

of

_the

dynamic

objects; and

(b)

the

parietal

regions and

the

tracking

of

the

visual

objects.

Key

words:

object

representatien,

coherency,

functiona]

MRI

We

have

previously

shown

that

the

representation

of

visual

objects

in

a

dynamic

scene requires

a

morc widespread neural system

than

that

for

a static scene.

This

neural system

extended

from

the

anterior

frontal

to

the

posterior

parietaL

brain

corticcs

(Ima-ruoka,

Saiki,

Miyauchi;

2005).

However,

_the

_precise

correspondence

between

the

brain

regions and

thc

various

cognitive

components, such as

the

tracking

ef

visual

ebjects,

the

maintenance of visual

informa-tion,

and

the

integration

of spatial

and

visual

infor-mation,

is

not

well

known,

The

aim

of

the

present

study

was

to

clarify

the

correspondence

between

a cognitive

process

and

the

neura] responscs

by

vary-ing

both

the

length

ef

_thc

occludcd

_period

of

the

dynamic

visual

objects

and

the

task

requirements.

Our

hypothesis

was

that

rnanipulation of

the

oc-cluded

duration

would

differentially

affect

the

*

College

of

Informatics

and

Human

tion,

Kanazawa

Institute

of

Technology,

gaoka

7-1,

Nonoichi-machi,

Ishikawa

921-8501,

Japan

**

_PRESTO,

_Japan

_Science

_and

_Technology

cy,

Kawaguchi,

Japan.

Graduate

School

of

matics,

Kyoto

University,

Kyoto,

Japan

***

_Brain

_Information

_Group,

_Kansai

_Advanced

search

Centcr,

National

Institute

ef

tions

and

Technology,

Kobe,

Japan

Cupyright

2005

ral

system

related

to

the

tracking

of

thc

object and

the

maintenance

of

visual

information.

That

is,

pro-longation

of

the

occluded

_period

would

_produce

an additional cost only

for

_the

maintenance

system and

shortening

the

occluded

_perjod

would

_produce

an

additional cost only

for

the

tracking

system.

Further-inorc we varied

the

task

requirements as

follows.

The

subjects were rcquired

to

maintain only color

information

in

one of

the

condjtions

(intrusjon

condi-tion)

and

te

maintain coherence

of

color

and spatial

information

in

the

other

condition

_(switch

condition}.

The

two

experimental

factors

would enablc

us

to

classify a number of

brain

regions

related

to

thc

representation of

the

dynamic

visual

objects.

Methods

The

participants

were

6

_paid

subjects who

_gave

their

informed

consenL

We

used

a

rnodified

version

of

the

MOPT

task

(SaikL

2003)

in

which

the

subjects were required

to

detect

a color change of

the

disks

while viewing

4

moving

disks

behind

4

stationary

gray

occluders,

The

stirr]uli

differed

trom

those

used

in

the

previous

study

in

the

following

two

experi-mental

factors.

Thc

first

difference

was

the

manncr

in

which

the

color changed,

In

the

switch

cendition

the

colors of

2

of

thc

4

disks

wcre

switched,

and

then

The Japanese Psychonomic Society

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The JapanesePsychonomic Society

110

The

Japanese

Journal

of

Psychonomic

Science

Vol.

24,

No,

l

Table

1

Brain

regions showing a significant color change effect or

interaction.

Main

gffect

Color

change

L/R

SFG,

SMA,

LIFG

Switch/Duration'

Intrusion/Duration*

IntrusionfDuration**

InteracEl'on

..

R

SFG

L

plP

RfL

alP,

R

plP

meee

o.6o'g

O.40pg

o.2og

o.oos

one

four

eight

Duration(sec)

Abbreviations.

L,

left;

R,

right;

SFG

superior

fronta]

_gyrus;

SMA,

supplementary motor area:

IFG,

infcrior

frontal

gyrus;

IP,

intraparietal

area;

*

_Longer

_duration

_induced

_highcr

activity. **

_Shorter

_duratLon

_induced

_higher

_activity.

switched

back,

within

the

stimu]us

display.

In

thc

intrusien

condition

however,

the

color

of

1

of

the

4

disks

was

changed

to

a

color

that

was selected

from

a

pool

of colors

other

than

the

4

original colors.

The

subjects were required

to

maintain

coherence

of

thc

color

and

spatial

information

of

the

disks

in

the

switch

condition,

but

to

rnaintain

onLy

color

informa-tion

in

the

intrusion

condition.

The

second

experi-rnental

difference

was

the

duration

of

the

occluded

period

(1

second,

4

seconds, or

8

seconds>

in

the

MOPT

time

series.

We

measured

the

brain

activitv

during

the

task

usrng a

1.5T

functional

MRI

scanner.

We

only

assessed

the

effect

of

2

factors

on

the

brain

regions

that

were

activated

by

the

MOPT

task

in

our

previous

study

(Imaruoka,

Saiki,

&

Miyauchi,

2005),

The

effects were measured with

an

estimate

of

the

parameter

values

obtained

in

the

individual

analysis

of

the

functional

imaging

data.

Results

and

Discussion

Of

the

10

interesting

regions

8

regions

had

a

sig-nificant

main effect

of

Coler

Change

or a significant

interaction

of

two

factors

(Table

1;

Figure

1).

As

shown

in

Table

1

and

Figure

1,

the

effect

of

duration

length

was

not

identical

across

the

intcresting

re-gions,

The

maintenance cost

in

the

switch condition

,OO,80.60.40.20,ooone

Du

Figure

1.

Parameter

estimate

value

obtained

from

interested

regions.

Upper

fig.,

right superior

frontal

gyrus;

Lower

fig.,

right

_pesterior

parietal

sulcus.

was

found

only

in

the

right superior

frontal

_gyrus

(Figure

1)

suggesting a close relationship

between

that

region and maintenance

of

bound

representa-tion

of

color

and

spatial

information,

In

contrast,

the

tracking

cost was

found

in

most

_parietal

regions

(Table

1;

Figure

1)

suggesting

a elose

relationship

bctween

spatial

processing

and

the

parietal

regions,

References

Imaruoka,

T.

Saiki,

J.

&

Miyauchi,

S.

2005.

ing

coherence

of

dynamic

objects

requires

nation

of

neural

systems

extended

from

anterior

frontal

to

posterior

parietal

brain

cortjces.

Neuro-image,

26,

277-284.

Saiki,

J.

2003,

Feature

binding

in

object-file

tatiuns

of

multip]e

moving

items.

fou･r7ial

of

Vision,