neural correlates of woman face processing by 2-month-old infants.tzourio-mazoyer, 2002 copia

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phere at a similar location, but its volume did not

each t he threshold for significance). Besides this right

nf erior temporal gyrus focus, this network includedilateral inf erior occipital and parietal areas. More-

ver, one should note that the lef t inf erior f rontal anduperior temporal gyri were activated during f ace pro-

essing.

DISCUSSION

The main finding of the present study is that

-month-old inf ants activated a network of areas be-

onging to the core system for f ace perception identifiedn adults (Haxby e t a l ., 2000). In particular, the acti-

ated area located within the inf erior temporal gyrus

earby the occipitotemporal sulcus is very lik ely to behe homologue of the adult f usiform f ace area (FFA)

efined by Kanwisher (Kanwisher e t a l ., 1997; Gau-

hier e t a l ., 2000a). As a matter of f act, despite existingiff erences between 2-months-old inf ant and adult

rain anatomy, the anatomical location of the inf erior

emporooccipital activation focus in inf ants was verylose to that of the FFA as reported in Kanwisher

eminal paper (Kanwisher e t a l ., 1996). Interestingly,he adult FFA, more active during processing of f aces

han of any other ob ject (for review see Table 3 and Fig.), is at the center of a debate. Some authors consider

hat

it

is s

pecia

lized for

f a

ces

(Kan

wish

er

, 2000) wh

ilethers think that it is domain general and related to

the acquisition of expertise in ob ject discrimination

(Gauthier e t a l ., 1999, 2000a,b; Tarr and Gauthier,

2000). Within this debate, one could argue that evi-

dence of FFA activation in inf ants, as early as 2

months of age, provides a developmental argument for

the domain specificity of this region, since f aces is thefirst perceptual category of complex ob jects with which

an inf ant becomes an expert at. However, since f aces

constitute the dominant visual stimulus to which in-

f ants are exposed during their first 2 months of lif e,

FFA activation at 2 months could as well reflect the

inf ants general expertise in ob ject discrimination. Nev-

ertheless, it can be assumed that it is related to indi-

vidual f ace processing rather than f acedness recogni-

tion inasmuch as it has been shown that in 12-week

inf ants f acedness can be categorized by either hemi-sphere despite a lack of interhemispheric coordination

(de Schonen and Bry, 1987). In addition, a recent study

in adult has shown that while the right FFA supports

individual f ace matching based on internal configura-

tion, its lef t hemisphere homologue is involved in

matching f ace parts (Rossion e t a l ., 2000). This is con-

sistent with behavioral data in 4- to 10-month-old in-

f ants showing a right-hemisphere advantage in f acerecognition (de Schonen and Mathivet, 1990; Deruelleand d e Schonen, 1998). As previously proposed (de

Schon

en an

d Math

ivet

, 1989),

th

e r

ight h

emis

ph

er

eadvantage of the f ace area in adults (Gauthier e t a l .,

TABLE 2

Brain Areas Activated on Average in a Group of Six 2-Month-Old Inf ants

during Face Processing Compared to Diode Fixation

Anatomical localization

Diodes condition

NRCBF (SD)

Faces–diodes NRCBF

increase (%)

Activatedvolume (mm3

)

rontal

L inf f rontal gyrus 67.0 (16) 12.8 792

L inf f rontal gyrus, orbital part 64.9 (10) 13.7 672R mid f rontal gyrus, orbital part 77.6 (21) 13.5 602

R medial superior f rontal 56.5 (16) 13.1 1656

R median cingulate 103.4 (8) 13.3 806

R ant cingulate, orbital part 83.4 (16) 12.1 182ccipital and temporal

L sup occipital 105.0 (14) 12.5 418

R sup occipital 112.5 (16) 15.2 677

L inf occipital / middle temporal 61.7 (22) 12.4 182

R inf occipital / middle temporal 106.2 (10) 13.1 154

L sup temporal 100.9 (8) 14.4 2404

R sup temporal 107.5 (12) 13.2 489

L inf temporal 55.4 (17) 14.8 308

R inf temporal gyrus /f usiforma 87.2 (12) 12.6 224ar

ieta

lPrecuneus 110.7 (14) 12.4 259

R inf parietal 105.1 (17) 12.4 201

N o t e . For each activated area, the table gives its anatomical location (based on the identification of ma jor sulci and gyri on one of the inf ant

MRI t hat was used a s a template), t he normalized regional cerebral blood flow (NRCBF) in the area during the diodes condition, its volume,nd the average NRCBF variation amplitude during f ace processing. L, lef t; R, right; inf , inf erior; sup, superior; mid, middle.

a The activated area homologue to the adult f usiform f ace area.

457RAPID COMMUNICATION



999) might then well be related to its earlier f unc-

ional maturation.We k now f rom anatomical (Brody e t a l ., 1987) and

metabolic studies (Chugani and Phelps, 1986; Chuganit a l ., 1987) on human cerebral maturation that at thege of 2 months the most myelinated and highest met-

bolic areas are located within subcortical structures

nd primary cortices, while the temporal cortex as a

whole shows a low metabolic activity. In such a region,

oor

ly matur

e at th

e a

ge of 2 months

, th

e s

yna

pt

icensity is f ar below the adult level and f ar f rom its

peak (Huttenlocher and Dabholk ar, 1997). UsingNRCBF during the diode condition as an index, wecompared the cerebral blood flow values of the right

FFA cluster with that of the right precentral region.This region is k nown to have high glucose metabolism(Chugani e t a l ., 1987) and myelination (Brody e t a l .,1987) at this age and can thus be considered as rela-

tively mature. In order to do so, we identified the pre-

central and postcentral sulci and manually defined on

th

e MRI t

emplat

e th

e pr

ecentra

l r

egion

. Nor

ma

lizedcerebral blood flow of the right FFA was found 30%

FIG. 1. Network of a reas active during f ace processing as compared to fixation of diodes in a group of six 2-month-old inf ants. Activatedreas (orange) a re superimposed on a series of transaxial structural slices t ak en f rom an inf ant MRI brain template. Colored tick s indicateelected anatomical landmarks: anterior limit of the occipital lobe (black ), rolando sulcus (red), and occipitotemporal sulcus (green). The

dentification of these anatomical landmarks was obtained on the template brain with a sof tware allowing a 3D reconstruction and sulci

rawing in any incidence. These and other landmarks were used to draw structural volumes of interest, such as the inf erior f rontal gyrus

orresponding in the lef t hemisphere to Broca’s a rea in adults (pink ), middle f rontal gyrus (yellow), and superior f rontal gyrus (white) that

ere used for activation anatomical labeling. The graph gives for each inf ant the variation of normalized regional cerebral blood flow values

uring the diode and f ace conditions in the cluster enclosed in the blue boxes that corresponds to the adult f usiform f ace area. L, lef t; R, right.

58 RAPID COMMUNICATION



ower than that of the precentral gyrus (right FFA,7 12; right precentral gyrus, 123 8, P 0.003;

aired t test, 5 d f ). This result can be tak en as an

ndication that the metabolic maturation of this region

evel was lower that that of the precentral gyrus. Onehould note that the comparison of these blood flowalues was undertak en in the diode condition. Theame comparison during the f ace condition showed a

imilar trend, the activated right f usiform area stillaving lower NRCBF values than the precentral gyrus

right FFA, 104 13; right precentral gyrus, 119 6,P 0.07; paired t test, 5 d f ).

Therefore, a ma jor finding of the present study is

hat, despite a low level of metabolic activity, this

isual associative cortex shows some relatively special-

zed f unctional activity. This demonstrates that f unc-

ional maturation does not require metabolic and ana-

omica

l maturat

ion

complet

ion

in th

e in

volved cort

ica

lreas. It indicates the anteriority of f unctional matu-

ration which might proceed simultaneously in severalconnected and active cortical regions. This hypothesis

is consistent with the idea that synaptic stabilization is

a crucial aspect of neural specialization (Changeux,1983).

Besides FFA, f ace perception by 2-month old inf ants

activated a bilateral inf erior occipital area correspond-

ing to the occipital f ace area previously identified in

adults as involved in early perception of f acial f eatures.Both this region and the FFA belong in adults to thevisual analysis of f aces core system, as defined byHaxby, which also includes the superior temporal sul-

cus (STS) that is consistently activated in adults (Ser-

gent e t a l ., 1992; Puce e t a l ., 1996; Kanwisher e t a l .,1997; Chao e t a l ., 1999a,b; Hoff man and Haxby, 2000;

Haxby e t a l ., 2000). Interestingly, the latter region was

not activated in 2-month-old inf ants, consistent with

its

putat

ive f un

ct

iona

l r

ole in th

e a

du

lt

bra

in

, na

melyto respond to changeable aspects of f aces, perception of

FIG. 2. Comparison of FFA locations reported in the literature, both in stereotaxic space and in single sub jects. Metanalysis of FFA

cations described in the stereotaxic space are displayed on the axial (40 mm, a) and sagittal (53 mm, d) slices on the SPM single sub ject

MNI template, corresponding to the mean coordinates of the FFA activations; white dots correspond to the extrema listed in Table 3. (b) FFAcation defined in a single sub ject on one of his axial brain MRI slice (Kanwisher e t a l ., 1996). (c) Activated f usiform gyrus a rea detected in

he present study superimposed on the template MRI of a single 2-month-old inf ant, in the same incidence as b. (e) Location of the right FFA

ctivation during f ace matching defined in a single sub ject and displayed on one of his brain MRI sagittal slice (Clark e t a l ., 1996). (f)

ctivated f usiform gyrus area detected in the present study in the same incidence as e.

459RAPID COMMUNICATION

neural correlates of woman face processing by 2-month-old infants.tzourio-mazoyer, 2002 copia

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