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Abstract:
PET with [15oxygen]water was used to assess rCBF during
spatial working memory (SWM), and spatial attention (SA) tasks.
Normal volunteers maintained fixation while attending to upper
right or left visual fields for a target (asterisk appearing
briefly on a flashing checkerboard pattern). After 40 seconds
subjects indicated whether a test stimulus was in the same location
as the target. In separate conditions the target occurred early in
the 40s stimulation interval, requiring SWM for most of the
interval, or late, predominantly requiring SA. The checkerboard
also flickered at slow and fast rates in different conditions to
identify bottom-up, stimulus-driven processes. Preliminary analysis
of 9 subjects (20 will be run) subtracting SA from SWM conditions
found differences between SWM and SA in frontal lobe only at the
fast flicker rate. SA conditions had higher rCBF in the thalamus at
both flicker rates. Prominent differences between SA and SWM were
found in parietal lobes and cerebellum at the slower flicker
frequency. These preliminary data indicate that with identical
stimulus and response parameters, relatively subtle changes in task
demands for attention or working memory cause activation of
different brain regions. Results will be discussed in relationship
to the regional specificity for executive functions and other
attention and working memory subprocesses of the frontal lobe and
interconnected regions of parietal lobe, thalamus, and
cerebellum.
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