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Abstract:
Abstract: Executive functioning has been conceptualized as
either a unitary attention-allocation system or as a set of
definable modules each responsible for a different sort of
processing. Here we tested whether one can identify separable
components of executive functioning having to do with switching
from one task to another. Participants had to keep internal count
of two streams of objects, and these counts could either increment
or decrement. Successive trials in this task required (a) no
switching between objects or between incrementing or decrementing,
(b) switching between objects but not between operations, (c)
switching operations but not objects, or (d) switching both objects
and operations. Behavioral data in these four conditions were
unambiguous in revealing that each type of switch added an
increment to response time, and that the increment for switching
objects was statistically independent from the increment for
switching operations. We also tested participants while they were
scanned using EPI/BOLD fMRI in a 1.5T scanner in this same task.
There were substantial regions of overlapping activation when
comparing the two types of switches. In addition, however, there
were regions that showed greater activation for object than
operation switching, and vice versa. The imaging and behavioral
results suggest that there are two dissociable components of task
switching that can be identified with partially differing
anatomical mechanisms.
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