The effects of brain lesions on the performance of bilateral arm movements

An experimental study of the effects of brain lesions on the performance of bilaterally synchronous tapping movements and movements of manipulative skill was undertaken. The subjects were 40 patients with verified left- and right-sided hemisphere lesions and 20 control subjects. The results show that left-sided cortical lesions produce significant impairment in the rapidity of repetitive movements with the ipsilateral as well as with the contralateral arm, whereas right-sided lesions produce impairment of movement in the contralateral arm only. The findings in the test of precise arm movements indicate that there is significant impairment in each arm in the presence of right- as well as of left-sided cortical lesions. Comparison of unilateral with bilateral tapping movements shows that movements performed by normal subjects with the two arms together are significantly slower than the same movements performed by either arm alone. In the patient group there is no significant difference between the rapidity of bilateral arm movements and that of the same movements performed by the left arm alone. The present experiments also indicate that the performance of patients with cortical lesions involving intrahemispheric extensions shows comparatively less reduction in respect of the rapidity of bilateral arm movements than does that of patients without such intrahemispheric involvement. The findings further reveal that bilateral performance of precise movements is significantly slower than the same movements performed by either arm alone, in the control group as well as in the patient group with either left- or right-sided cortical lesions. Some theoretical interpretations of the findings are discussed. On a entrepris une étude expérimentale des effets des lésions cérébrales sur les performances de “tapping” bilatéralement synchrones et de mouvements de manipulation. Les sujets étudiés comportaient 40 malades avec lésions vérifiées hémisphériques droites et gauches et 20 sujets de contrôle. Les résultats montrent que les lésions corticales gauches entraînent un déficit significatif dans la rapidité des mouvements répétitifs aussi bien avec le membre supérieur ipsi-latéral qu'avec le membre supérieur contro-latéral, tandis que les lésions droites n'entraînent un trouble du mouvement qu'au niveau du membre supérieur contro-latéral. Avec le test des mouvements fins, on constate un trouble significatif, à l'un et l'autre membre supérieur lors des lésions corticales dro