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Abstract:
Abstract: Overwhelming evidence indicates that the
hippocampus plays a critical role in long-term declarative memory.
In contrast, the role of the human hippocampus in working memory,
particularly when information needs to be maintained only for a few
seconds, remains controversial. Using positron emission tomography
(PET) we show robust activation of the right anterior hippocampus
proper during the performance of both object and spatial
alternation tasks. Hippocampal activation emerged even though
subjects only had to remember a single, simple stimulus over a
minimal delay of 1 second. A high-resolution PET single-subject
mapping study confirmed that the focus mapped to the anterior
hippocampus proper and not neighboring parahippocampal regions. The
activity does not appear to reflect the maintenance of information
over the delay, since we found no hippocampal activation when the
delay was increased to 5 seconds. The hippocampal activation may be
related to unique features and demands of alternation tasks. These
data are the first to demonstrate human hippocampal involvement in
a working memory task and conflict with the entrenched belief that
the human hippocampus only participates in long-term memory.
Results are particularly striking given the pervasive difficulties
neuroimaging experiments have had activating the hippocampus proper
using a wide-range of tasks with substantially greater mnemonic
demands.
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