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Abstract:
Abstract: Apraxia is a disorder of skilled movements not
induced by weakness or movement disorders such as ataxia, tremor,
or dystonia. In right handers, apraxia is more commonly associated
with left than right hemisphere lesions. The performance of skilled
movements requires not only learned motor programs, but also a
variety of basic motor skills such as precision, posturing, speed,
and the ability to sequence a series of movements. This study used
a series of motor tests to investigate the role of cortical versus
subcortical structures (basal ganglia and subcortical white matter)
in mediating these functions in patients with left hemisphere
ischemic strokes and matched control subjects. We found that when
compared to the patients with cortical lesions, those with
subcortical lesions were more impaired on the motor tasks that
require precision and speed, such as performing the pegboard task
and finger tapping. In contrast, patients with cortical lesions had
more difficulty replicating fixed postures and with nonsense hand
sequences that may be considered a sequence of hand postures.
Overall, these findings demonstrate that the left hemisphere's
cerebral cortex is important for overall organization of movement
sequences including successive changes in hand and limb posture,
while the left hemisphere's subcortical region is important in
precision and speed.
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