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Abstract:
Previous neuroimaging studies have implicated frontal and
medial temporal regions in episodic memory encoding, with some
evidence indicating that the left and right hemispheres
differentially contribute to verbal and nonverbal encoding,
respectively. The present study used event-related fMRI methods to
directly compare verbal and nonverbal encoding within subjects. In
each fMRI scan (BOLD fMRI, 3.0T GE scanner with ANMR EPI, 16 axial
slices, TR=2 sec), situationally novel and situationally familiar
pictures and words were incidentally encoded. There were four trial
types: novel pictures, familiar pictures, novel words, and familiar
words. For all trials, participants made an indoor/outdoor
judgment. Results revealed that, compared to familiar pictures,
novel pictures elicited greater activation in parahippocampal,
fusiform, lingual, and right inferior frontal cortices. Compared to
familiar words, novel words elicited greater activation in
parahippocampal, fusiform, and left inferior frontal cortices.
Importantly, the parahippocampal regions engaged during word
encoding were a subset of those engaged during picture encoding.
The present results converge with previous demonstrations that left
and right inferior frontal regions appear to differentially
contribute to verbal and nonverbal encoding (Kelley et al., 1998;
Wagner et al., 1998). Furthermore, overlap within posterior
parahippocampal regions was observed during verbal and nonverbal
encoding, which suggests that the mnemonic functions of these
regions are not restricted to a particular stimulus class.
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