Dolcos, F.1,2,
Graham, R.3, Prince, S. E.1,
Rice, H. J.1, LaBar, K. 1,
Cabeza, R.1
1. Center for Cognitive Neuroscience,
Duke University., Durham, NC, USA
2. Centre for Neuroscience, University of Alberta, Edmonton, AB,
Canada
3. Department of Psychology, University of Alberta, Edmonton,
AB, Canada
Emotional events tend to be better
remembered than nonemotional events. This phenomenon has been attributed
to a modulatory effect of emotional arousal during encoding and consolidation
(modulatory hypothesis). We investigated this hypothesis using event-related
fMRI. Female participants were scanned during incidental encoding
of high-arousing (pleasant and unpleasant) and low-arousing (neutral)
pictures. Recall of the pictures was tested after scanning and, as
expected, was better for high-arousing than for low-arousing pictures.
To reveal brain regions involved in successful encoding operations,
we compared brain activity for subsequently remembered and forgotten
pictures (subsequent memory effect). Analysis showed that, compared
to low-arousing pictures, the subsequent memory effect for high-arousing
pictures was associated with greater activity in medial temporal,
prefrontal, lateral parietal, and occipitotemporal areas, brain regions
that are commonly associated with encoding. The subsequent memory
effect was also affected by emotional valence: for pleasant pictures,
it was greater in the left prefrontal cortex, whereas for unpleasant
pictures it was greater in the right prefrontal cortex, consistent
with the valence hypothesis, which proposes that in prefrontal areas
pleasant emotions are mainly processed in the left hemisphere, whereas
unpleasant are processed in the right. In summary, these results suggest
that emotional stimuli exerts their beneficial effect on memory by
enhancing activity in brain areas commonly associated with encoding,
and both arousal and valence modulate this effect, consistent with
the idea that the left and right prefrontal areas are differentially
involved not only in the general processing of emotional information
but also in successful emotional encoding.
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