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Abstract:
(tm)Department of Psychology, Rutgers University, Newark
Previous studies have suggested that the basal ganglia play an
important role in category learning, since patients with
Parkinson's disease were impaired on a probabilistic categorization
task. In this task, subjects learned to associate four discrete
stimuli with a category outcome. However, other studies have
indicated that Parkinson's patients experience difficulty shifting
attention between cues. Thus, it is possible that the Parkinson's
deficit on this task is related to an attentional deficit, not a
deficit in category learning per se. Here, we attempted to clarify
the nature of the category learning deficit in Parkinson's using a
probabilistic categorization task formally similar to the earlier
task, but where the cues were presented as features on a single
stimulus. Under these conditions, we found two distinct sub-groups
of control subjects. Solvers learned the task faster and reached
higher levels of performance than in previous studies, while
non-solvers performed worse than in previous studies, and reached
less than 70% correct performance. Overall, Parkinson's patients
were impaired on this task, performing similarly to control
non-solvers. These results suggest that probabilistic category
learning tasks may be solved by different strategies in controls
(e.g. single-cue learning, configural learning), and that
Parkinon's disease may lead to a tendency to adopt a less
advantageous learning strategy.
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