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Abstract:
Face working memory tasks commonly require subjects to (1)
encode face information, (2) maintain that information across a
delay, and (3) determine if that face matches a probe face. While
the mnemonic portion of this task has been given considerable
attention, little is known about the neural mechanisms involved
with match/nonmatch decisions. In the present study, event-related
functional magnetic resonance imaging (fMRI) measured activity
during the response period of a face-recognition task as the match
status of a probe stimulus varied. In the context of a face delay
response task, differences in fusiform face area (FFA) and anterior
cingulate cortex (ACC) activity reflected whether the probe face
matched one of the remembered faces. We found greater activity in
the FFA when the probe face matched a remembered face. Primate
single-unit studies have observed that single neurons in
inferotemporal cortex demonstrate stimulus-selective 'match
enhancement' at probe; this result demonstrates a human correlate
of match enhancement which averages across stimulus-selective
neural assemblies. In contrast, activity in ACC was greater when
the probe face did not match the remembered face. The 'fast-same'
reaction time effect indicates that nonmatches might require a
higher degree of cognitive control than matches; the present result
suggests the need for a broader definition of the types of
cognitive control monitored by the ACC.
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