2P056 カエル網膜における同期的周期的発火の阻害が視覚誘発性逃避行動に与える影響(2003年度 日本基礎心理学会第22回大会優秀発表賞)

The Japanese Psychonomic Society

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The JapanesePsychonomic Society

f}le_{foPanesefournatof}Jlsychonomic Science

2004,VoL23,No.1,109-1lO

Summary

ofAwarded

Presentation2P056

Pharmacological

suppression

of

oscillatory

synchronized

discharges

in

retinal

_ganglion

cells

inhibits

escape

behavior

of

the

frog

Mie

GANGI,

Yasuhiro

HoRIucHI,

Shoko

HoNDA,

Hiroshi

IsHIKANE,

and

Masao

TAcHIBANA

tiniversi",

of

Tokyo*

Inthe frogretina

OFF-sustained

type

_ganglion

cells

(dimrning

detcctors)_generate oscil]atory

synchronized discharges with a ]ight which isdimming, To elucidate the

function

of the

oscillatory synchronization

(OS)

in

the

retina we performed

behavioral

experiments and

multi-electrode recordings from

dirnming

detectors.

Frogs

exhibited an escape

behavier

when an

expanding dark spot was presented on a computer monitor, The _probabilityof

the

escape

behavior

was

higher

as the

final

size of the expanding dark spot was jncreased.

Multi-electrode

recordLngs

from

theisolatedretina revealed

that

the

OS

was enhanced as the

final

size of the expanding dark spot was increased. The

OS

could

be

blocked

when the isolatedretina was superfused with

bicuculline,

a

GABA,x

receptor blocker. Injectionef bicuculline into _the eyes of the

frog

sig-nificantly suppressed the escapc behavior

but

did

not affect theoptok{netjc responses toa drifting

grating. We conclude

that

the

OS

of

dimming

detectors

in

the retina

is

esscntial fortriggeringthe

escape behavior,

Key words: oscillatory synchronization, escape

behavior,

retinal gang-lion cell

Introduction

The stimulus-evoked oscillatory synchronization

(OS)

of neural assemblies

has

been

described

inthe visuaE systems,

but

the functiona[roles of this

phe-nomenon remain to

be

elueidated. Inthe frogretina OFF-sustained type _ganglion cells

(dimming

detec-tors)generate the

OS.

The

OS

depends

on the size

and spatial continuity of the dimming stirnuli, and is

suppressed bybicucullinc,aGABAA receptor blocker

(Ishikane

et aL 1999).

Frogs

exhibit visually evoked

escape

behavior

when a looming object is_presented

(Waldeck

&

Gruberg,

1995) and dimming

detectors

are assumed to be related te thisescape

behavior

(King

et al. 1999).To elucidate the

functional

roleof

the

OS

in

the retina we examined how the escape

behavior was modulated when the OS was

sup-pressed

by･

bicuculline.

* _{Department of Psychology,}

_Graduate

_School

of Humanities and

Sociolegy,

University of

Tokyo,

7-3-1

Hongo,

Bunkyo-ku,

Tokyo

O033

Methods

Behavioralexperiments

A bull[rog was _placed in a transparent acrylic

dome and

its

escape

behavier

was examined

by

ma-nipu]ating the finalsize

_(visual

angle, 10-55e) ef an

expanding dark spot which was displayed on an

LCD,

The

optokinetic response was mcasured as the

maximum angle of

head

rotation when a vcrtical

square _grating

(spatial

frequency,

O.1cycles _per

de-gree) drifted horizontally

(tempora]

frequeney,

O-O.16Hz),

An

ocular

injection

of

bicuculline

was given under anaesthesia, and the behavioral experi-ments were performed after recovery from the

anaes-thesia

(2

hours

after administration),

Electrophysiological experiments

Spike

discharges were recorded from dimming de-tectorsof theiselatedfrogretina with a _planar

multi-electrode array,

Expanding

dark

spots were

pre-sented on a

CRT

and projected onto the rctina through an optjcal system. The _propertiesof the sti-rnuli were thcsame as those used forthe behavioral experiments.

Sliding

window cross-correlograms

The Japanese Psychonomic Society

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The JapanesePsychonomic Society

110 The

Japanese

Journal

of Psychonomic

Scicnce

Vol

were computed from the spike discharges to

evalu-ate the temporally correlated activities,

Results

Sizedependence of the escape behayior and the

OS

of dimming detectors.

Behavioral

exPeriments

An expanding

dark

spot _pre$ented on the LCD could evoke the escape

behavior,

The _probabilityof

the escape behavior was

higher

as the

final

size of the

expanding dark spot was increased,and when the

spot diameter was

larger

than

500

the

_probability was saturated,

ElectroPhysiotogicalept)eriments

Spike discharges totheexpanding dark spot were

recorded from

dirnrning

detectors

and

cross-correlograms were computed, The

OS

was

detected

when the

final

size of the spot was approximately 30",and thestrength of the

OS

increased as thefinal

sizeof thespot was

larger.

These

results suggested a

strong correlation

between

the strength of the

OS

and the _probabilityof the escape

behavior.

Effectof a GABAA receptor blocker on the

OS

and

the escape

behayior.

ElectroPhysiologicalemperiments

We examined the effccts of bicucullineon the re-sponses of

dimming

detectors.Bicuculline

increased

the number of spike

discharges

but suppressed the

OS

completely even when the

largest

spot was

pre-sented.Behaviorat emperiments

We exarnined the effects of

bicuculline

on

the

es-cape

bchavior

to the largcst expanding dark spot.

Just

after theocular

injection

of bicucullinethe

prob-abj]ity of the eseape behavior was significantly

re-duced

(Figure

1). One day after the

injection

the escape

behavior

recovered

to

the

contrel leveL

Sup-pres$ion of the behavior was not observed after an

injection

of standard saline,

We

observed that

bicu-culline

did

not affect the optokinetic responses to

drifting

_gratings,

These

results indicate that the

reduction of the escape

behavior

could

be

attributed

tosuppression of the OS of dimrning detectors

in

the

retina.

.23,

No.

1

L-9-g8gg

o.s86.b.z-89

O.O

a-

_Control

_Bic

_Washout

Figure

1.

Reduction

of the _probability of the

escape behavior after the

injection

ef

cuculline

(Bic).

Control,

before

the

injection.

Washout, 24 hours arter the

injection.

Error

bars,

S,E,M,

Discussion

The present results

demonstrate

that thc OS of

dimming

detectors

in

the retina

is

essential

te

trig-gering escape behavior. Because thestrength of the OS depends on the$timulus size, the OS may encode

the stimulus size.

When

a predator

is

approaching,

frogs

must escape. On the other hand, when small

insects

are

flying

nearby,

frogs

might attack them,

It

therefore seems tobe a

feasible

assumption thatthe

information

cocled by theOS of dimming

detectors

in

the retina may

be

used to regulate the behavior of

frogs.

References

Ishikane,

H.

Kawana,

A.

&

Tachibana

M. 1999

rt- and

long-range

synchronous activities in

ming detectorsof thefrogretina.

Visuat

enee, 16:1001-1014.

King,

J,G.Jr.

Lettvin,

J,Y.

&

Gruberg, E.D. 1999

Selective,

unilateral, reversible lossof behavioral

responses to]ooming stimuli after

injection

of

rodotoxin of cadmium chloride

into

the

frog

uptic

nervc. Brain Research,841i 20-26

Waldeck,

R,

F. Gruberg, E.R. 1995 Studies en the

optic chiasm of theleopard frog.I.Selective

loss

of

visually elicited avojdance

behavior

after optic

chiasm hemisection.Brain.

Behavior

and Evolution,

46:84-94,