Perception of face parts and face configurations: an FMRI study

Abstract

fMRI studies have reported three regions in human ventral visual cortex that respond selectively to faces: the occipital face area (OFA), the fusiform face area (FFA), and a face-selective region in the superior temporal sulcus (fSTS). Here, we asked whether these areas respond to two first-order aspects of the face argued to be important for face perception, face parts (eyes, nose, and mouth), and the T-shaped spatial configuration of these parts. Specifically, we measured the magnitude of response in these areas to stimuli that (i) either contained real face parts, or did not, and (ii) either had veridical face configurations, or did not. The OFA and the fSTS were sensitive only to the presence of real face parts, not to the correct configuration of those parts, whereas the FFA was sensitive to both face parts and face configuration. Further, only in the FFA was the response to configuration and part information correlated across voxels, suggesting that the FFA contains a unified representation that includes both kinds of information. In combination with prior results from fMRI, TMS, MEG, and patient studies, our data illuminate the functional division of labor in the OFA, FFA, and fSTS.

Figure 1

Stimulus manipulations. The 2 × 2 design involved orthogonal manipulation of the presence versus absence of face parts (eyes, nose, and mouth; horizontal axis) and face configurations (the placement of these parts in a face arrangement vs. scrambled arrangement; vertical axis). External contours were either intact or removed.

Figure 2

Face-selective regions, the OFA, FFA, and fSTS, from an fMRI localizer scan (p < 10⁻⁴, uncorrected) in the right hemisphere of a typical subject, shown on a flattened surface. Sulci are shown in dark gray and gyri in light gray. Talairach coordinates and statistics for each ROI from a group analysis (right hemisphere): OFA (BA 18), coordinates = 46, −78, −7, voxel number = 118, max t value = 4.6; FFA (BA 37), coordinates = 43, −53, −12, voxel number = 71, max t value = 3.9; fSTS (BA 22), coordinates = 60, −51, 9, voxel number = 259, max t value = 6.3.

Figure 3

Responses of the FFA, the OFA, and the fSTS to face parts and configurations. Featural effect (left): The stimuli were pooled by the presence (black) versus absence (gray) of face parts. The hemodynamic responses of the face-selective regions were averaged across voxels, stimulus categories, and subjects. The y-axis indicates the percent signal change. The error bars show the standard error of the mean of the BOLD responses across subjects. Configural effect (right): The stimuli were pooled by whether stimuli contain veridical face configurations or not.

Figure 4

The correlation of the configural and featural effect in the FFA from a typical subject. (A) The featural effect was significantly correlated with the configural effect indexed by t values across voxels in both the right (r = .29) and left (r = .24, not shown) FFA. (B) Distribution of correlation coefficients for randomly shuffled pairs of configural and part effect across voxels pooled from both the right and left FFA. The vertical dotted line indicates the mean value (r = 0) of the correlation coefficients from the permutation test, and the solid line indicates the observed correlation coefficient.