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Abstract:
Recent functional neuroimaging studies have shown the
importance of the medial temporal lobe (MTL) in conjunction with
the inferior frontal gyrus (IFG) in memory encoding. The magnitude
of activation evoked in IFG and MTL predicted how well study items
were later remembered. Differences in activation that predict
subsequent memory, Dm effects, have also been demonstrated with
event-related potentials using directed forgetting. By instructing
participants to either remember or forget, rather than relying on
endogenous variability in encoding, we control for distinctiveness
differences among stimuli that could have previously been
correlated with successful encoding. Particularly distinctive
stimuli may evoke additional visual processing that is correlated
with subsequent memory. Participants performed five runs each
containing 60 study items. Half the study items were cued as
remember trials and half were cued as forget trials. In addition,
half the study stimuli were words and half were faces in order to
examine stimulus-type effects in memory encoding. Each trial lasted
3 seconds (1500 ms word or face stimulus, 1500 ms remember or
forget instruction). The intertrial-interval was varied across
trials by including blank trials (33% trial periods were fixation
points). Consistent with previous findings, encoding contrasted
with directed forgetting elicited greater activity in the right and
left anterior hippocampus, left IFG, and parahippocampal gyrus.
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