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Abstract:
Previous neuroimaging studies have claimed that item and
order recognition utilize different neural regions. In these
studies, subjects knew the type of test they would later receive,
therefore, the different regions used at retrieval may have been
due to differential encoding of items in the two conditions. To
overcome this limitation, we measured regional cerebral blood flow
(rCBF) in 8 young healthy volunteers while they performed item and
order recognition tasks but were unaware of the type of test until
after encoding. During baseline conditions, subjects read
previously studied words without the instruction to recognize them
(which allowed incidental or automatic retrieval). The results
showed significant rCBF increases in frontal (BA 6/8) and parietal
(BA 7/19) cortices when order retrieval was contrasted with item
retrieval or baseline. We also observed lower rCBF in the medial
orbital frontal cortex (BA 10/11) and the hippocampus during order
retrieval than during item retrieval or baseline conditions. The
differential involvement of these areas in item and order
recognition cannot be due to a confounding effect of distinct
encoding strategies. In addition, they were associated with
intentional retrieval unconfounded by incidental or automatic
retrieval. Thus, intentional retrieval of order information
activates some brain areas while suppressing others utilized during
item retrieval. This suggests that memory for item and order
information is mediated by separate neuroanatomical networks.
6B
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