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Abstract:
Abstract: Prior experience with an object facilitates
subsequent performance with that identical object (ID), and with an
object that has the same name, but a different physical form (SN).
We use event-related fMRI to investigate these two types of
priming. Whole brain, gradient-echo echo planar images were
collected (5 mm axial slices, TR = 3 sec) on a 1.5 Tesla scanner.
Object pictures were presented briefly (200 msec), randomly
intermixed for repetition type (ID, SN), with a repetition lag of
~30 sec. For half of each run, subjects (N=10) performed a semantic
decision task (natural vs. man-made) and for the other half they
performed a phonological decision task (one vs. two or more
syllables). Relative to a visual noise baseline, both decision
tasks activated a number of regions including occipitotemporal
cortex bilaterally (OT) and left inferior frontal (LIF) cortex.
Whereas both ID and SN repetitions resulted in reduced OT activity
across both tasks, the decrease was stronger for ID than SN
repetitions. Moreover, across tasks, ID, but not SN, repetition
resulted in reduced activity in LIF. In addition, differential
task-related priming effects were observed in left temporal, LIF,
and left premotor cortices. These findings are consistent with the
idea that reduced activity in posterior cortex reflects perceptual
learning whereas reductions in anterior regions reflect increased
efficiency in linking lexical and perceptual
representations.
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