Development of asymmetrical cortical responses to radial expansion/contraction(Summary of Awarded Presentation at the 25th Annual Meeting)

(1)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

The

jopanese

.lournal

of Psl,c'honomic/Sc'ience

2D07,

Vol.

25,

No. 2,275-276

Summary

ofAwarded

PresentationIP22

Development

of

asymmetrical

cortical

responses

to

radial

expansion/contraction

*Nobu

SHiRAia･b,

Deirdre

BiRTLEsC･d,

John

WATTAM-BELLC,

Masami

K. YAMAGucHIa･e,

So

KANAzAwAf,

Janette

ATKiNsoN`

and

Oliver

BRADDicKd

Chuo

Uitiversit)'a,

Japan

SocieCl'

for

the

P?'omotion

_of

Scienceb,

Lrhiversity

CoUage

LondonC,

L)niversity

of

Oxfbrdd,

laPan

Science

and

Technotog:y,

Agenaye,

Shukutohu

Universityf

We

report

the

development

of cortical responses

(stcady-state

visual evoked

_potentials:

VEP$)

to

radial

expansionlcontraction,

Forty-four

3-4-month-olds

and

9 aclults

viewed

moving

dots

which cyclically

(2.085

Hz)

alternated

between

radial

expansion

(or

contraction) and random

directional

motion,

The

first

harmonic

(Fl)

response

in

the

VEPs

must arise

from

global-motion-sensitive mechanisms.

The

results

indicated

that

the

Fl

ampljtudes

for

contraction were

sig-nificantly

larger

than

those

for

expansion

for

the

4-month-olds

and

the

adults

but

not

for

the

3-month-olds.

Thesc

results suggest

that

the

human

cortical motion mechanisms

hai,e

an asymmet-rical sensitivity

for

radial expansion/contraction which

devclops

at around

3 to

4

months of age,

Key

words:

Infant

vision,

cortical

processing,

radial

cxpansion/contraction, visual

evoked

tials

Radial

expansion

or contraction is a motion

pat-tern

typically

produced

by

an observcr's o",n or an

objecVs

motion-in-depth.

Such

radial motions are

highly

significant

for

animals

te

control

various

adaptive actions, such as

locomotton,

reaching, or

avoidance

of a collision with obstacles,

In

the

pre-sent study, we examined

the

early

development

of radial motion cortical sensitivity

in

human

iniants,

Method

Partieipants

Twenty-two

3-month-o]ds

(mean

age=93.5

days,

SD=9.0)

and

22 4-rnonth-olds

(mean

age=125.3days,

SD=8,9)

participated.

They

were

healthy

fu]1-term

infants

and

born

within

14 days

from

due

date.

The

infants

showed

no

strabi$mus

or

significant

refractive

error.

Nine

adults

(mean

age=

23.6 _years,

SD

=3.3)

also

participated

and

were

tested

*Department

_of

_Psychology,

_Chuo

_University,

742-1

Hachiohji-shi,

Tokyo

192-0393

This

research

was

supported

by

Medical

Research

Council

{UK)

programme

gTant

G7908507

to

Profs.

Janette

Atkinson

and

Oliver

Braddick,

and

Dr.

John

Wattam-Bel],

and

Grant-in-Aid

for

Scientific

Research

from

the

Japan

Society

for

the

Promotion

of

Science

to

Nobu

Shirai

_(l7-741},

Copyright

2007

in

the

same waN, as

the

infant$,

"

Stimuli

We

uscd

dynamic

dot

patterns

which

al-ternated

between

radial expansion

(or

contraction)

and

random

directional

motion

(Figure

la),

Within

each stimulus sequence,

the

dots'

trajcctories

alter-nated

between

a radial and random

direction

every

240

ms,

Hence

the

overall aLternation

frequency

ol

the

stirnulus

was

2.085 }-Iz.

Each

stimulus was

eom-posed

of

2OOO

moving

white

dots

<dot

diameter=O.37

deg

for

infants,

O.26 deg

for

adults}

distributed

on a

black

_presentation

field

(for

infants,

width=48.7

deg,

hcight=36,5

deg;

for

adults width=34

deg,

height

=-25.5

deg),

All

of

the

dots

moved

at

a

constant

veloc-ity

of

6.8deg/s,

Each

doVs

lifetirne

was

set

at

12 frames

(120ms),

with

]ifetimes

initialized

at

each

motion

_pattern

alternation.

There

were

two

stimulus conditions

in

the

_present

study: expansion-random motion

alternation

and

contraction-random

motion

alternation.

Apparatusandprocedures

The

apparatus and

procedures

of

the

_present

study were

almost

the

same

as

thosc

of

Braddick

et

aL

(2005),

The

stimuli

were

presented

on a

17-inch

CRT

monitor

{refresh

ratc=100Hz, resolution=800 ×

600pixels).

The

viewing

distance

was approximately

40

cm

for

the

The

Japanese

Psychonomic

Society.

All

rights reserved.

(2)

The Japanese Psychonomic Society

NII-Electronic Library Service

TheJapanesePsychonomic Society

276 .lgE:s:.a..6s::･e-tit8

The

Japanese

Journa]

o

(a)

Petternrevers]lrare=1.0BSHz [1[yde=480ms) -K

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Figure

1. (a)

A

schematic

illustration

of

{c)

those

of

Fl

amplitudes.

infants

and

57 crn

for

the

adults.

The

VEPs

were

recorded

with

three

_gold

cup electrodes: one on

the

vertex, one

1

cm above

the

inion,

and

a

ground

elec-trode

_positioned

high

on

the

forehead

(for

more

de-tail

see

Braddick

et

aL,

2005).

Once

the

pattern

appeared

on

the

monitor,

the

infant's

attention was attracted

to

the

screen

by

a small noisy

toy

that

courd

be

shaken

in

front

of

the

screen

_throughout

_the

recording,

The

experimenter

controlled

the

averag-mg

process

with

a

hand

held

switch.

Whenever

the

infant's

attention

shiited

from

the

direction

of

_the

screen,

the

experimenter

halted

the

sampling

until attention was redirccted

_toward

_the

stimulus,

Sam-pling

continued

until

200 $weeps

had

been

recorded.

The･

amplitude

and

_phase

of

the

averaged

signal

compenent at

the

_pattern

alternation

frequency

(Fl

=2.085

Hz,

the

fundamental

harmonic

_of

the

_sweep

frequency)

was

measured.

The

presence

of a

stati$ti-cally significant

VEP

signal

at

this

frequency

was assessed

by

the

circular-variance

test

(Moore,

1980;

Wattam-BelL

1985),

Each

infant

participated

in

two

VEP

recording runsi

one

session

with

expansion-randorn

stimuli and one with contraction-random motion stimuli.

Each

adult

_participated

in

six

VEP

recording runs:

three

with

expansion-random

stimuli

and

three

with

contraction-random

motion

stimu]i.

Hence

data

for

each

motion

condition

from

each

adult

participant

was averaged

irom

three

record-[ti8{-gf':18.ytstss

f

Psychonomic

Science

Vol,

25,

No.

2 (b)

(c)

lwlvnNOVAtAGEut,MeT/ON) /etemdinnbct-'eenAG["ndMOT/ON pf:.os

Z'2

eo

_;t

4o

wh...

e

p.Epgi

3rnenths 4months Adult AduJr

CN=21) CN=12] (N=g] {N!]2] CN

±

1?] {N=g)

Agegfoups

Agegroupa

the

stimulL

(b)

Results

of analysis of

Fl

significance,

and

ings

₍₆₀₀

sweeps

in

_total).

Results

and

Discussion

Figure

lb

shows

the

percentage

of

_participants

who showed

a

significant

_(circular

variance

test,

at

leastP<O.05)

Fl

response

in

each motion

condition.

The

4-month-olds

and

the

adults showed

large

differ-ences

between

the

expansion

and

contraction

condi-tions.

These

results

suggest

that

the

hurnan

visual

sy$tem

has

a

bias

towards

contraction under

_the

experimental

condition

of

the

_present

study.

To

examine

_this

contraction

bias,

we

compared

the

mean

Fl

amplitudes

for

the

expansion and

contrac-tion

conditions

{Figure

lc).

While

both

the

4-month-olds

and

the

adults showed significant

differences

between

the

Fl

amplitudes

for

expansion

and

for

contraction,

_the

3-month-olds

did

not show sig-nificant

difference

between

expansion and

contrac-tion,

_These

results

suggest

that

the

cortical

motion mechanisms

have

an asymmetrical

_processing

_to

ra-dial

expansion/contraction,

and

that

this

cortical

processing

develops

between

3

and

4

months

of

ages,

Reference

Braddick,

O. Birtles,

D. Wattam-Bel],

J. &

Atkinson,

J. 2005

Motion-

and

orientation-specific

cortical

responses