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Abstract:
Abstract: Functional MRI (fMRI) is increasingly being applied
to determine hippocampal involvement in episodic memory function in
the intact human brain. While fMRI evidence has corroborated lesion
and PET findings for hippocampal participation in encoding
processes, few fMRI studies have addressed hippocampal function in
retrieval. It is also unclear whether specific hippocampal regions
differentially mediate encoding and retrieval processes. We
employed whole-brain event-related fMRI to investigate hippocampal
activity during encoding and recognition of complex visual scenes
in 14 neurologically healthy adults (7 female). Participants
learned 38 scenes and later identified these items during scanning
from 76 scenes that included 38 never-seen distractors. Familiar
(learned) pictures activated bilateral anterior hippocampus and
left posterior hippocampus. Novel (never-seen) pictures also
activated right anterior and left posterior hippocampal areas,
however, the magnitude of the activation associated with encoding
was smaller than that associated with recognition. These data
support the hypothesis that both anterior and posterior regions of
the medial temporal lobe, particularly the hippocampus, are
involved in memory encoding (see Schacter & Wagner,
Hippocampus, 9, 7-24, 1999). It also suggests that retrieval
processes are not limited to posterior medial temporal structures,
but may in fact engage the hippocampus more strongly than encoding
in anterior and posterior regions.
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