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Abstract:
The fusiform face area (FFA) has been shown respond
selectively to faces. In this set of experiments, we tested which
components of the face contribute to the selectivity of this
response: the presence of internal features (eyes, nose, mouth),
configuration, or external features (hair, jaw line). The
hemodynamic response of the functionally localized FFA was measured
for stimuli in which we orthogonally varied whether the "face"
contained (I) real internal features versus solid black ovals in
the corresponding locations; (II) veridical face configurations
versus rearranged nonface configurations; and (III) intact external
features versus a square cutout showing the central face region.
Subjects were run in either a 1.5T or 4T scanner, and asked to
fixate and passively view the stimuli while undergoing
event-related MR imaging. The stimulus order was counterbalanced
within each run and across eight runs. The data suggest that
different components of the face contribute in a roughly linear
additive fashion to the FFA response: only the veridical face
elicited a full-amplitude response, and with fewer components the
response decreased in amplitude. This pattern of results is
strikingly different from that seen in a parallel study using MEG:
while the M170 response showed a strong influence of external
features, no one component contributed to the FFA signal more than
others. This different response profile in the FFA could reflect
later stages or areas of face processing.
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