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Abstract:
Abstract: Parkinson patients, patients with focal lesions in
the left dorsolateral prefrontal cortex, and control participants
were tested on a task-switching paradigm. Four spatial
stimulus dimensions were used: position, direction of an arrow,
direction of motion, and spatial word ("LEFT" or
"RIGHT"). In Experiment 1, a single
dimension was presented on each trial and was either the same (no
switch) or different (switch) as on the previous trial. The cost
associated with changing the task-relevant dimension was higher for
both patient groups compared to controls. In Experiment 2, two
dimensions were presented on each trial, and a cue indicated the
relevant dimension, allowing the evaluation of specific processes
involved in task switching. The patients performed comparable to
the controls on two assays of inhibition (e.g., a perseveration
condition in which the relevant dimension became irrelevant across
successive trials). However, the prefrontal patients and
to a lesser extent the Parkinson patients, were impaired on
transitions in which an irrelevant dimension became relevant (i.e.,
dimensional negative priming). This pattern suggests a
similar deficit in both groups related to attending to information
that had previously been irrelevant rather than a deficit in
inhibitory control. Current testing is being conducted with
patients with lesions in right dorsolateral prefrontal cortex to
examine if these patients will exhibit an inhibition-specific
deficit.
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