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Abstract:
Abstract: Despite widespread interest in working memory (WM),
debate continues on its functional anatomy. Studies differ on the
degree to which spatial and verbal WM are right or left lateralized
and use overlapping or distinctive cortical areas. We asked 20
normotensive men and women aged between 50 and 70 to view letters
presented singly and located at one of eight spatial positions.
Instructions determined whether they responded 1) differentially to
presentation on either side of the screen, to a 2) letter or 3)
position that was one of three memorized, or to a 4) letter or 5)
position identical to one presented 2 prior in the series. Two
replications of the 5 tasks were studied with O water PET.
Normalized cortical blood flow (CBF) from task 1 was subtracted
from other tasks to derive rCBF related to the increase in working
memory between tasks 2,3 and tasks 4,5. Spatial and verbal vectors
were then compared using inclusive and exclusive masking options in
SPM99. Spatial WM distinctively induced greater right superior
parietal rCBF; verbal WM distinctively induced greater left
prefrontal and medial frontal rCBF. Heightened bilateral prefrontal
and parietal rCBF were common to spatial and verbal WM. Results in
this older sample supported separate, lateralized stores for
spatial and verbal information coordinated by a common
parietal-frontal network manipulating stored information.
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