| |
Abstract:
To test among hypotheses of prefrontal function, we have
developed a task that can be performed by young children as well as
adults and that permits demands on working memory, inhibition, and
task switching to be independently varied. We report the first in a
series of experiments using this task. Three conditions alternated
with passive visual fixation periods. In all conditions, a target
appeared randomly on the left or right. In the Congruent condition,
subjects pressed the response button on the same side as the cue
(C1). In the Opposite condition, subjects pressed the button on the
side opposite the cue (C2). In the Mixed condition, C1 & C2
were randomly intermixed; this required working memory (holding two
rules in mind) and inhibition (resisting the tendency to always
respond on the same side as the target). We scanned 8 normal adults
(ASE, head coil, TR = 2 sec, 7mm coronal slices, 160 images per
slice per condition). Dorsolateral prefrontal cortex was
significantly more active in the Mixed condition (i.e., when both
working memory and inhibition of a prepotent response were taxed)
than in either of the other conditions. Further experiments are in
progress using variations of the task that test whether this result
is found when demands on working memory or on inhibition are
minimized.
|
