2-B-06 盲点におけるフィリングインの異方性(2002年度 日本基礎心理学会第21回大会優秀発表賞)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

TheJLtpaneseJburnatofRsJ,chonomicScience

2003, Vol,22,No, 1,45--46

Prizewinner's

Summary2-B-06

Anisotropy

of

_{perceptualfi11ing-in}

at

the

blind

spot

YukyuARARAGi

and

Sachio

K],ushu Uitiversits,*NAKAMIZO

We

found

an anisotropy of perceptual"fi11ing-in"

at thephysiological

blind

spot.

The

stimulus

was apairof

lines

presented

for

200

ms with ene

line

en each side ofthe

blind

spot.

The

length of

the

lines

extended gradually whenever an observer pushed a

key

on a computer

keyboard,

The

observer's taskwas toreport whether the

line

appeared tcomplete'

or `gapped'

when compared to

a reference line_presented sirnultaneously _{tothe tcmporal} retina. The

indcpcndcnt

variable was the orientation of the line.The results with

9

ebservers showed that the minimum length of the linefor_perceptual

fi11ing-in

increased

systematically as

the

orientation of

the

lines

changed

from

the horizontaltotheverticaL We suggest thatthisanisotropy isdue to theelliptic shape of the receptive fie]dsof thebinocular neurons thatcontributc to_perceptual fi11ing-inat theblindspot.

Key words: anisotropy, perceptual

fi11ing-in,

blind

spot

Introduction

The blindspot isan area of theretina where photo-receptors are not present.

But

we

do

not perceive

any _gap

in

thevisual

field

which corresponds tothe

blind

spot even

in

monocular vision. This

is

because

thevisual system complements a lackof visual input

at the

blind

spot: a _phenomenon which

is

called

perceptual fi11ing-in,When a pair of linesis

pre-sented, with one lineon each side of the blindspot, we _perceive a continuous line.This _perceptua]

com-pletionof _thelinerequires _the lincs_to

be

a suMcient

length.

Recently

Okuma

et aL

(2001)

have reported

that the minimum

length

ef the

lines

which is

re-quired forperceptual fi11ing-independs on their

ori-entatien: that

is,

shorter

horizontal

lines

were

re-quired

for

perceptual

fi11ing-in,

than were required

when the lineswere vertical. The _present study

investigatedthe anisotropy of _perceptualfi11ing-inat

the

blind

spot

by

changing the orientation of the

lines

from

O

degrees

(horizontal)

to

90

degrees

(verti-cal),

*

_Behavioral

_and

_Health

_Sciences,

_Graduate

Schools

of Human-Environrnent Studies,

Kyu-shu University, 6-19-1 Hakozaki, Higashi-ku,

Fukuoka 812-8581

Experiment

Method

Observets

Nine

observers with normal or

cor-rected-to-normal visual acuity, _participated

in

the

'expenment.

Stimuli and Apparatus The stirnuli used in the

experiment are

il]ustrated

in

Figure

la,

The

stimu-luswas apairoflineswhich were presented with one

on each side of the blind spot of the right eye. A

reference

line,

which was a continuous

line',

was pre-sented tothe temporal retina with equal retinal

ec-centricity, and was used as a criterion on which to

judge

perceptual fi11ing-inof the blind spot, Both

lineswere _presented for200 ms and their lengthwas

gradually extended whenever theobserver pressed a

key

of thecomputer keyboard. The width of both

lineswas 1.7degrees and

the

luminance of both lines and the background were O.3and 78.1cd!rn2,

respec-tively.

The

stirnuliwere presented on a

19-inch

color

monitor

(IIYAMA

MA90IU).

A

computer

(FMV

ME

3/507) controlled the_presentation of thestimuli and recerded the responses of the _{participants.}

Procedure

Before

theexperimental trialsthe

re-gion of the b]ind spot inthe right eye of each

ob-server was measured. Each observer was asked

to

fixateon a

displayed

fixation_peint,and topress a

key

of the

keyboard

until the gapped

line

appeared

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

46 The

Japanese

Journal

of Psychonomic Science VoL 22,No. 1

-Reference

Line

Fixation

.

12o"

900

_6oo

1500.yS

:

<..

30"

ri

soO-:N

l:.

oe

'

si"N

'

(a)

Figure

1,

(a)

The

stimulus and

each lineorientation.

{b)

The means an

line

for

perceptual

fi11ing-in,

orientations of the

lines.

Amovw='Tm[LL9EmEo"o.EJ

₅ 4 3 2 1 o

StimulusLine

o 3o 6o go 12o 150 ISO

Orientation

ofLines

(deg)

(b)

reference

lines

_presented

to

the

blind

spot and

the

temporal retina

for

d standard deviations

(thin

lines)of theminimurn ]engthof the

averaged over the nine observers and _plotted as a

function

of the

reference line.The orientations of the lineswere O,

30,60,90,120,and 150 degrees. The observer

per-formed

36

trials

(6

orientations

in

each of

6

sessions),

Ineach session the 6 orientations of the linewere

presented ina random order foreach observer. The

experiment was conducted ina

darkened

room ancl

the

distance

between

the

display

and the eye of an

observer was 3e cm. The observer's head was

stabi-lizedwith a bite-board and their lefteye was

oc-cluded.

Results

and

Discussion

The experiment

demonstrated

an anisotropy of

perceptual

fi11ing-in

at theobserver's

blind

spot] that

is,

the minimum

length

of the

line

for

the _perceptual

fi11ing-inchanged as a function of the line

orienta-tion. Figure lbshows themeans and standard

devia-tions

Qf the miniinum

line

length

for

perceptual

fi1-ling-in,averaged over the 9observers, and plotted as

a function of

the

orientation.

The

results

_pf

a one-way repeated measure

ANOVA

indicated

that the

effect ef the orientation of the linewas stati$tica]ly

significant

(F(5,40)=4,06,

p<O.O05).

Multiple

com-parison tests also revealed that _the minimum line

length was shorter when the]inewas oriented at O

degrees than when the linewas oriented at 60,

90,

or

120

degrees,

Thesc

results clearly

indicate

that

in

theanisotropy of _perceptual fi11ing-inthe minimum

linelength increasesina systematical manner from

thehorizontaltothe vertical orientations.

The

anisotropy

found

in

the presentstudy may be due totheelliptic shape of thc reccptivc fieldsof the

binocular neurons inVl that contribute to

percep-tual

fi11ing-in

at

the

blind

spot

(Kornatsu,

Kinoshita,

& Murakami, 2000), These neurons tend tohave

very largeelliptical receptive fieldswith a horizontal

axis

longer

than

the vertical axis.

References

Komatsu, H. Ktnoshita, M. & Murakami, I.2000

Neural respenses in

the

retinotopic representation

of the

blind

spot

in

the

macaque

Vl

to

stimuli

for

perceptual

fi11ing-in.

Ibur7ial

of

IVeuroscience,

20,

9310-9319.

Okuma,

M.

Ninose,

Y.

Nakamizo,

S.,

&

Kondo,

M

2001 Measurement of

the

blind spot and

temporal property of _perceptual completion.