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Abstract:
This study examined the pattern of activity during the delay
period of a visual recognition memory task (delayed
nonmatch-to-sample) using functional magnetic resonance imaging.
Seven adults participated in 2 test sessions. For the encoding
phase, stimuli (abstract patterns) were presented for 3-s. The
stimulus then disappeared (memory condition) or remained on screen
(control condition) for 12-s. In both conditions, the old and new
stimuli were presented during the recognition test phase. Subjects
pressed a button corresponding to the new stimulus. Thus, to make
the correct response in the memory condition, subjects had to
maintain an accurate representation of the stimulus during the
delay. For the control condition, subjects only had to make a
perceptual comparison between stimuli and press a button
corresponding to the new stimulus. Analysis was confined to the
12-s delay phase. Subtraction of the control from the memory
condition revealed a common pattern of activation in 13 or 14 of
the 14 sessions: the striate and extrastriate cortex showed
widespread, bilateral activity; areas within the parietal region
and the left temporal lobe were also active. Finally, in 12
sessions, the right dorsalateral prefrontal cortex was active.
Thus, multiple structures are involved in maintaining visual memory
during a delay and some of the same structures required for
perception are also involved in memory.
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