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Abstract:
To what extent do asymmetries in motor behavior reflect
lateralization of motor planning? A series of experiments were
performed with split-brain patient J.W., in an attempt to evaluate
the contributions of the left and right cerebral hemispheres to
solving the problem of movement selection.All tasks involved
choosing the most natural option for interacting with a dowel,
appearing in a variety of different orientations. No actual
movements were allowed. In the grip selection task, J.W. was
required to determine which end of the dowel his thumb would be on
if he grasped it using a designated hand. In the hand selection
task, J.W. was told which end of the dowel his thumb should be on,
but was free to select either hand. Finally in the arm selection
task, J.W. determined which end of the dowel the elbow of a
designated forearm would be toward if he aligned it with the
stimulus. Responses in these tasks were compared with J.W.'s
performance in analogous tasks involving actual movements. The left
hemisphere was more accurate in selecting movements consistent with
those actually executed. This advantage was most pronounced for
responses based on the contralateral (right) limb, but was also
apparent for the ipsilateral limb. These findings support the
hypothesis that the left hemisphere plays a dominant role in
solving the problem of movement selection.
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