Experimental studies on the relationship between brain pathology and abnormal motor behavior

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Clinical pictures of abnormal motor behavior were described objectively through rigorous psychological experiments. The fo1lowings are the findings based on the relationship between those clinical pictures and results of lesion analysis by MRI.1. Abnormal motor behaviors due to 1esions in posterior association areaPosterior association area is considered as a site where visual, somesthetic, and auditory sensations cross over each other and are further integrated to fulfilll complicated functions. It was found that : (1) Lesion in upper posterior association area causes pure agraphia and somesthetic dyslexia, which suggests that literal somesthetic image may be represented in this area ; (2) Lesion in lower posterior association area causes ideomotor apraxia and/or ideational apraxia ; (3) Lesion in medial posterior association area causes axial sensory disorder (pathology around precuneus on each side) or topographical disorientaton (pathology from right precuneus to posterior region of cingulate gyrus).2. Abnormal motor behaviors due to prefrontal lesionsPrefrontal lesions can cause imitation behavior, utilization behavior, compulsive manipulation of tools, alien hand sign, hypergraphia, and grasping phenomenon. All of these are related to the patient's intention or will. As the prefrontal area is connected to basal ganglia and 1imbic system, it is possible that prefrontal lesions produce disorder of intention and will. Considering the relation between the prefrontal area and the subcortical structures, a neurological model was proposed for explaining praxis and its disorders.