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Abstract:
The behavioral significance of the postcentral gyrus has
remained uncertain in spite of a great number of studies designed
to clarify its function. We reported a 49 year-old right-handed
man. MRI showed a laminar necrosis on the caudal half (Brodmann
1-2) of the lateral portion of the left postcentral gyrus. He
showed no detectable disturbance in elementary sensations or in
almost all-intermediate sensations. But both shape discrimination
and object recognition was destroyed in the right hand. Further
more, functional MRI is used to investigate the neural basis for
shape discrimination of 13 normal right-handed Japanese subjects.
The five wooden objects (cylinder, cube, sphere, prism and cone)
were selected as stimuli. In the MRI machines, the subjects were
instructed to palpate each shape carefully with the left hand. If
they palpated the cone, they made a short extensiof the left middle
finger. As compared as the results of the control task, the right
caudal parts of the postcentral gyrus and right superior parietal
lobule areas were activated when the subjects discriminate shape.
These fMRi findings and the case study above suggest the caudal
parts of the postcentral gyrus regions play an essential role in
the process of shape discrimination.
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