|Budget Amount *help
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥700,000 (Direct Cost: ¥700,000)
I investigated pathological grasping phenomena and related prehensile behavior in 34 patients with recent damage to a unilateral medial hemispheric wall from stroke. Phenomena were categorized as either the grasp reflex or the instinctive grasp reaction. The instinctive grasp reaction was subdivided into clothing reaction, final grip, trap reaction, magnet reaction, and visual groping. To determine the exact location and extent of the lesions, I examined magnet resonance images. The patients with damage involving the supplementary motor area, especially its caudal part, constantly exhibited the grasp reflex, mainly in the hand contralateral to the lesion. On the other hand, in the patients with damage involving the anterior cingulate gyrus, especially its middle and caudal parts, the groping movements such as the magnet reaction and visual groping of the instinctive grasp reaction were observed, mainly in the hand contralateral to the lesion. Other varieties of the instinctive grasp reaction were observed in the patients with damage to either the supplementary motor area or the anterior cingulate gyrus. These observations indicate that the grasp reflex is modulated mainly by the caudal part of the supplementary motor area, while the groping movements are primarily controlled by the middle and caudal parts of the anterior cingulate gyrus. I also found that some patients manifested, in addition to grasping movements, typical compulsive manipulation of tools placed on the table or shown before them, with the hand contralateral to the lesion. These patients continued to use objects until they restrained the movements using the other obedient hand. Such patients had severe, extensive damage to the anterior cingulate gyrus adjoining the genu and anterior body of the corpus callosum, as well as the callosal involvement.