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Abstract:
Current models of basal ganglia anatomy posit the existence
of multiple parallel, anatomically segregated circuits. Anatomical
data from nonhuman primates suggest that the circuits subserving
motor functions are segregated from those subserving cognitive
functions. Here we present data that demonstrate that in humans,
motor and cognitive fronto-subcortical circuits are segregated. We
studied a group of patients with Parkinson's disease undergoing
surgical lesioning of the globus pallidus internus for relief of
their symptoms. Lesion location along an anteromedial (AM) to
posterolateral (PL) axis was found to be related to post-surgical
outcome on both cognitive and motor measures. Performance on
several measures of working memory, as well as proactive
interference in memory, was linearly related to distance along this
axis, with AM lesions leading to post-surgical impairment,
intermediate lesions having little effect, and PL lesions leading
to an improvement on several measures. In contrast, bradykinesia
had a nonlinear relationship to lesion location, with intermediate
lesions leading to greater post-surgical improvement than lesions
in more extreme AM or PL locations. These data support the
segregation of functionally distinct circuits in the human
pallidum.
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