P-2A-9 カエル網膜ディミング検出器における周期的発火の生起と刺激依存性(2001年度 日本基礎心理学会第20回大会優秀発表賞)

The Japanese Psychonomic Society

NII-Electronic Library Service

TheJapanesePsychonomic Society

7ke/

.fuI)anesekJumat

_of

ltsJ,t.'honvtnic.'

Stienc'e

L,DOZ,

VoL

ZI,

No.

1,

47-48

Prizewinner's

SummaryP-2A-9

Synchronous

oscillations

in

frog

retinal

Hiroshi

IsHiKANE,

Mie

GANGi

and

Masao

Uhaiversity

of

7't)kyo'

ganglion

cells

TACIIIBANA

To

investigate

how

visual

information

is

coded

by

cell

_populations,

we simultaneously

record-ed

right-evoked

spike

discharges

from

multiple

OFF-sustained

type

_ganglion

ce]ls

(the

dimming

detectors)

of

the

frog

retina using a

_planar

multi-electrode array.

Auto-

and cross-correlation analyses were

performed

to

evaluate

temporal

properties

of

the

spike

trains.

With

full-field,

sinusoidally modulated

diffuse

illumination,

cross-correlation analysis reveared

the

_presence

of

long-range

synchronous oscillations.

The

strength of

the

synchroneus oscillations

depended

on

the

spatial

_properties

of

the

light

stimulus,

which

extended

far

beyond

the

"classical"

receptive

field

that

is

defined

by

the

spike

discharge

rate.

These

resu]ts suggest

that

synchronous oscMations may

encode

_global

features

of

visual

stimuli

and

_play

a

key

role

in

_perceptual

integration.

Key

words:

frog,

retina,

_ganglion

ceil, synchronous oscillatien, stimulus

dependence,

temporal

coding,

_population

coding

Introduction

The

Gestalt

psychologists

assumed

that

the

visual

system would automatically

link

the

related

_parts

together

to

form

the

objects

in

a visual scene.

Recent

studies

have

revealed

that

visual cortical neurons

show

synchronous

oscil]atory

activities

that

depend

on

coherent

features

in

the

visual

field

(fo.r

a

review,

see

Singer

&

Gray,

1995).

These

results

support

the

hypethesis

that

synchronous oscillations may serve

to

bind

the

distributed

neuronal activities

into

a unique

representation.

Frog

retinal

_gang]ion

cells also show

long-range

synchronous oscillations

(Ishikane

et al.,

1999)

.

In

the

_present

stucly, we examined

the

stimulus

dependence

of synchronous oscil]ations so

that

we

could

understand

infermation

coding

by

cell

popula-tions.

Methods

Spike

discharges

were recorded

from

multiple

OFF-sustained

type

_ganglion

cells

(the

dimming

"

_Department

_of

_Psychology,

_Graduate

_School

_of

Humanities

and

Sociology,

University

of

Tokyo,

7'3-1

Hongo,

Bunkyo-ku,

Tokyo,

113-O033

detectors)

of

the

isolated

frog

retina with a

planar

multi-electrode array.

We

sometimes obsenred

sev-eral

spikes

with

different

amplitudes

and

waveforms

'

'

from

a single channel,

To

isolate

spikes originating

'from

a

_given

neuron,

the

template-matching

tech-nique was used.

The

stimulus

images

were

_generated

on

a

CRT

djsplay

which

was

driven

by

a

PC

and

projected

onto

the

retina

through

optics.

Auto-

and

cruss-correlograms

were

computed

from

the

spike

discharges

'to

evaluate

temperal]y

correlated

activ-ities.

In

this

study,

the

intensity

of

light

stimuli was

sinusoida]ly

(O.25Hz)

_Inodulated

under all

condi-tiOllS.

Results

Oscillatory

actiyities

are

generated

by

spot

illumi-nation

which

is

larger

than

the

receptive

field

of

the

dimming

detectors

To

examine

the

effects of spot size on

the

oscillatory activities,

the

center of

the

spot

illumination

was adjusted

to

the

center of

the

elassi-cal receptive

field

of

the

cell.

The

spot

intensity

was

sinusoidalry

modulated

while

the

background

inten-sity was maintained at

the

mean

level

of

the

modula-tion.

As

the

spot,size was

increased

up

to

the

recep-tive

field

of

the

cell,

the

number

of

spike

discharges

The Japanese Psychonomic Society

NII-Electronic Library Service

TheJapanesePsychonomic Society

48

.

The

Japanese

Journal

of

Psych

'

'

'

increased

almost

]inearly.

But

the

auto-correlogram

'

did

not

reveal

the

_presence

of

oscillatory

activities.

However,

spot

illumination

larger

than

the

receptive

field

could eveke

the

oscillatory activities

(N30

Hz).

A

further

increase

in

spot size strengthened

the

'

latory

activities

but

the

number

of

spike

discharges

'

'

did

not

increase.

The

generation

of synchronous oseillations

depends

on

the

stimulus

pattern

With

a

full-field

modulated

illumination,

cross-correlation analysis revealed

the

_presence

of synchronous oscMations

in

the

dimming

detectors,

The

synchronous

oscillations

were not

_phase-locked

to

the

stimulus onset

indicat-ing

that

these

activities

could

originate

from

neural

interactions,

SynchTonous

oscMations were

detected

even

in

cell

_pairs

more

than

2mm

apart,

However

synchronous oscillations were net

detected

when

two

distant

cells with non-overlapping receptive

fields

were

stimulated

with

respective

spots,

the

intensities

of which were sinusoidally modulated

in

phase.

XVhen

the

continuity

of

the

sinusoidally

modulatecl

full-field

illumination

was collapsed,

by

inserting

a slitwith

the

mean modulation

intensity

between

two

dimrning

detectors,

the

synchronous activities were weakened

but

not

abolished.

Discussion

In

this

study, we examined

how

synchronous

escil-lations

in

the

frog

retina were affected

by

stimulus

pattern.

Synchronous

oscillations

were

evoked

only

when

the

spot

size

was

larger

_than

_the

classical

receptive

field

of

the

dirruning

detectors;

This

result

suggests

that

synchronous oscillations among

the

climming

detectors

may serve

to

discriminate

the

size

of

visual objects

that

are

larger

than

each

classical

receptive

field.

The

decrease

of synchronous

oscilla-tions

by

spatial

discontinuity

supports

the

hypothesis

that

s}mchronous oscillations would encode

global

onomic

Science

Vol.

21,

No.

1

visual

features

covering many

receptive

fields.

The

frog

retina

transmits

a

highly

seleeted

and

transior-med representatien

to

the

brain

(Lettvin

et al.,

1959

;

Maturana

et al.,

1960).

It

would not

be

surprising

if

the

synchronous oscillations observed

in

the

frog

retina

contribute

to

hjgh-level

processing.

Our

results

indicate

_that

synchronous

oscMations

are

induced

by

long-range

neuronal

interactions.

The

intera6tions

might require

phase-locking

oscillatory

modules extending

horizontally

across

the

retina.

Amacrine

cells make widely

spread

meshworks via reciprocal

synapses,

er

gap

junctions.

Synchronous

oscillations could

be

_generated

by

these

neural

mech-anlsms.

Further

studies are required

to

understand

how

synchronous oscillations

in

the

retina contribute

to

the

functions

in

the

visual system.

'

Acknowledgments

This

work

was

supported

by

Grant-in-Aid

for

Scientific

Research

(12053212)

and

the

Special

Coor-dination

Funds

for

Promoting

Science

and

Technel-ogy

(the

Project

Neuroinformatics

Research

in

Vision)

from

the

Ministry

of

Education,

Science,

Sports

and

Culture,

and

from

the

_Japan

Society

for

the

Promotion

of

Science

(11480245)

to

MT.

References

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Tachibana,

M.

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