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Abstract:
Medial temporal lobe(MTL) has been suggested to be involved
in associative memory of stimuli presented as pairs. We
investigated the extent of involvement of MTL in encoding of
associative memory, using two different stimulus types, i.e., pairs
of unrelated pictures or words. Six H215O PET scans were performed
for each subjects (N=8) to measure rCBF during the associative.
During the scans, participants made decision of conceptual
relatedness in response to randomly selected picture or word pairs.
rCBF changes related with associative encoding of pictures or words
were compared to those of control scans where same/difference
decision was made based on shapes of pairs of geometric figures.
Following each scans, recognition test was given and no difference
was found in memory performance between stimulus types (picture-
91%, word-94%). Left inferior prefrontal, left cingulate cortex,
and bilateral occipital regions were activated both during picture
and word conditions. Right middle prefrontal activation was also
found during word condition. Significant stimulus type difference
was found in left parahippocampal areas where activation was
increased during picture association but decreased during word,
relative to control condition. These results suggested that left
MTL was selectively involved in picture association but not
word.
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