嗅覚刺激強度と先行手がかりの有無が眼窩前頭領域の血行動態に与える影響 : 近赤外分光法を用いた検討(第23回大会 優秀発表賞抄録)

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20e5,Vol.24,No.1,1t9 120

Summary

ofAwarded

PresentationIP48

Cue

availability

changes

the

orbitofrontal

activation

for

olfactory

stimuli

-A

NIRS

imaging

study

Takeo

KoNDo*,

Shiori

AoyAMA**,

Rie

FuKuMoTo**,

Yuri

SAITo**,

and

Tamotsu

TosHIMA**

Research

CenterforAdvanced

Scienceand Technolctgy',The Uitiversity

of

Tokyo* and Hiroshima

Uhiversity

**

Some

studies

have

reported thattheorbitofrontal cortex

(OFC)

increases

its

activation relative

tothe

intensit},

of an olfactory stimulus, On theother hand, some studies have suggested

that

this

phenomenon isnot observed. The _procedural

difference

of the

2

groups of

investigations

was the

concurrent presentation,or not, of an additional cue.

Our

study

focused

on this

difference

and

involved a neuro-imaging _{technique to}

investigate

_theeffects, on 6participants, of a verbal cue and

changes of o]factory stimulus intensjty. We observed that when the verbal cue was absent,

activation of the

OFC

was re]ated to the stimulus intensity.This result was

in

agreement with the

observations of _previous studies.

However,

although activatien of the

OFC

is

linearly

related to

the intensityof the olfactory stimulus when ether cues are _present thislinearrelationship may

become unclear,

Key words: olfaction, orbitofrontal cortex, near-infrared spectroscopy

Introduction

Several

neuro-imaging studies suggest thatthe

or-bitofrontarcortex

(OFC)

isa

higher

center

for

proc-essing olfactory stimuli. However, the

OFC

is

consid-ered to play various roles, not only

for

olfactc)ry sensor.v processing

but

also

for

accommodatjng adaptive behavior. Thus there issome disagreement about thereason

for

activation of the

OFC

when this

isevoked by olfactory stimulation. Although some

studies have suggested that OFC activation

(the

amount of blood

fiow)

would

increase

relative to

olfactory stimutus

intensity,

other studies

have

re-ported that the stimulus

intensity

did not

have

an effect on the amount ef activation. Insome

neuro-imaging studies which have measured the activation

of

the

OFC

evoked

by

olfactory stimulj, there

have

also been vocal, visual, or haptic cues concurrently

presented. However, because

the

OFC isinvolved in

*

_Barrier-Free

_Project.

_Research

_Centcr

_for

vanccd

Science

and Techno]egy, The University

of Tekyo, 4-6-1 Komaba, Meguro-ku, Tokyo

8904**

Department of

Psychology,

Hiroshima

sity, Kagamiyama 1-1-1,IIigashi-hiroshima

8524

associative learning, the use of these cues might mask any effects of changing thestimulus

intensity.

Indeed,an intensityeffect was observed

in

astudy in

which concurrent cues were not used

(Rolls,

Kringel-bach,& deATaujo,2003). However, theeffect has not

been observed instudies inwhich have used these

cues

(Royet,

Hudry,

Zald,

Godinot,

Gregoire,

Lav-enne,

Costes,

&

Holley,

2001; Anderson,

Christoff,

Stappen, Panitz,Ghahremani, Glover,

Gabrieli,

&

So-beL2003). Inthe _present study, we invcstigatedthe

effects of olfactory stimulus

intensity

and

presenta-tionof a concurrent cue on activation of theOFC.

Method

Participants

The

participants were 6 _graduate

and undergraduate students of Hireshima

Univer-sity. Allof the students had normal olfaction and

were right handed. Their average age was

23

years.

Materials

We

used r-undecalacton, which

has

a matured peach-likesmell,

from

a standardized

olfac-torystimulus set

_<Daiiehi

Yakuhin IndustriaL

Tokyo,

Japan)

to manipulate the intensityof the olfactory stimulus. Near-jnfrared spectroscopy equipment

(ETG-100,

Hitachi

Medical,

Tokyo,

Japan)

was uscd

to measure the amount of blood flow in the

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

120 The

_Japanese

_Journal

of

Psychonomic

Science VoL 24,No. 1

bitofrontal

cortex.

Procedure

The participants were instructed

to

breathe

naturally and keep theireyes closed.

The

olfactory stimuli were presented

3

times

for

each of

the strong and weak conditions by bringing a filter paper impregnated with r-undecalacton to within approximately

2

cm ofasubject's nose.

Each

presen-tationwas

for

15

secends, and thiswas followed by

30

seconds of rest, In one condition a cencurrent verbal cue was _presented. In

the

other condition the

verbal cue was not

_presented,

The order of

presenta-tionof the olfactory stimulus intensityand

the

ver-balcue was counterbalanced

between

participants.

Seven

measurernent _points

(channels)

on the

fore-head

of a each _participantwere used toinvestigate

thejrOFC hemodynamics

(oxy-Hb).,

The _positionof

thesechannels, according tothe

international

1O-20

method, covered the OFC region

(see

Figure 1).The sampling rate was O.5seconds.

Results

We calculated theaverage oxy-Hb values

from

3

to

10 seconds after thestimulus onset, and used these

values

in

our analysis,

We

then used a two-way

ANOVA,

with the stimulus

intensity

(strong,

weak} and the verbal cue

(presented,

not _presented)

,

both as within-subject

factors.

The

results

indicated

sig-nificant interactionsinchannel 1

(F(1,

5)=7.439,

P<

O.05)and channel 5

{F{1,

5)=6.892,P<O.05),

Discussion

The

results revealed that when the verbal cues

were not _presented,activation of the

OFC

was linear

with the stimulus intensity,On the other hand, when verbal cues were presented, activation of the

OFC

was not observed.

It

is

suggested thatwhen verbal cues were

_presented

the

_participants

may

have

used

thisinformation, which was more salient than the

olfactory stimuli, and

therefore

activation of theOFC was not observed.

Consequently,

the

results

indicate

o.e3 O.02 O.OlAEoEE o.oig

-e.o28O

I).03zg

-o.oaU

-O.05Za

o.o3oA O.02oa o.ol

:o=

-O,Olbe

×

-O.02o

.O.03

.o.oo

-O.05

H

FChannel

5

gt-rang-cu'e

1

TIME

(sec)

Figure 1,

Oxy

hemoglobin

changes

for

ulus

intensity

_{(strong/weak}}

and cue avail-abi]ity

(cuefnocue}

in

channel 1

(upper)

and

5

(lower).

thatactivation of the

OFC

reflects _processing of the

intensity

of an olfactory stimulus.

References

Anderson, A.K.,

Christoff,

K..

Stappen,

I.,

Panitz,

D.,

Ghahrernani,

D.

G.,

Glover,

G,

Gabrieli,

J.

D.,

&

Sobel,

N,,

2003,

Dissociated

neural representations

of

intensity

and valence in

human

olfaction. IVtzture

Neuroscience,

6,

196-202.

Rolls,E. T. Kringelbach, M, L,,

&

de Araujo, I.E.

2003. Different representations ef _pleasant and

unpleasant odours inthe human brain.Eumpean

JbuTmal

of

IVeuroscience,

18,

695-703,

Royet,

_J,

P,,Hudry,

_J.,

Zald,D, H.,Godinot, D,,

Gre-goire,M.

C.,

Lavenne,

F,,

Costes,N,,

&

Holley,

A,,

2001.

Functional

neuroanatomy of

different