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Abstract:
Studies of non-human primates have shown that activity in
left inferior temporal regions is decreased during recognition
memory. PET and fMRI studies in humans have revealed a set of brain
regions that show increased activity during recognition memory, but
less attention has been devoted to decreases in activity. Partly
this may be due to difficulties with differentiating between brain
responses associated with recognition memory versus novelty
detection. The purpose of the present PET study was to identify
brain regions that show increased or decreased activity during
recognition of pictures, and to see how these activation
differences corresponded to encoded-related brain activity. By
contrasting previously presented pictures (old) with new pictures
(new) increased activity was observed in posterior cingulate gyrus
and the precuneus. Of these regions, the posterior cingulate was
also activated during picture encoding (as compared to a low-level
reference task). Follow-up analyses suggested that this region was
specifically associated with successful retrieval. When new was
contrasted with old, decreased activity in left inferior temporal
gyrus, posterior cingulate gyrus, and right frontal cortex was
observed. Specific contrasts associated left inferior temporal
deactivation with recognition memory, and left hippocampal activity
with novelty detection. Taken together, these results provide
support that successful recognition memory is associated with
increased as well as decreased activity.
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