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Abstract:
We used a task-switching procedure to investigate whether
processes such as response competition and response selection are
carried out by distinct regions within lateral prefrontal cortex.
Participants classified stimuli by pressing a right or left
response key, according to their color or shape. The appropriate
task was determined by a "C" for color or an "S" for shape in the
center of each stimulus. We orthogonally manipulated three factors:
(1) Response competition: whether the stimulus dimensions indicated
the same or different responses. (2) Response selection: whether
there were 2 or 4 values of the relevant stimulus dimension. (3)
Rule activation: whether the trial required a switch from the task
performed on the preceding trial (e.g. color-shape) or not (e.g.
color-color). The behavioral data demonstrate RT effects of
response competition, response selection, and switching, and
distinct patterns of frontal involvement were associated with these
three factors, providing evidence for separable and localizable
task-switching processes.
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