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Abstract:
Abstract: This study used event-related fMRI to measure
changes in activity of the PFC and FFA as the memory demand
increases in a delay-response task for faces. The FFA in each
subject was defined as the set of voxels showing statistically
significant activation in a scan with passive viewing of faces
contrasted against passive viewing of objects. The PFC in each
subject was defined based on anatomic landmarks. Each
delay-response trial was composed of (1) a four-second encoding
period where the subject viewed four images (one, two, three, or
four faces, with the balance made up of scrambled faces) serially
presented, (2) an eight-second delay period where the subject
viewed a fixation cross, and (3) a two-second response period where
the subject viewed one face and gave a motor response to indicate
if that face matched one of the faces presented at encoding. During
each of the three task periods, all subjects showed activity in PFC
voxels that increases with increasing memory load. In most
subjects, activity averaged across the entire FFA increased with
increasing memory load during encoding and response; half of the
subjects showed similar increases during the delay. The key finding
of the experiment was that FFA activity was modulated by working
memory load under conditions where attentional and perceptual
demands were controlled.
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