Learning of a Unimanual Motor Skill by Patients with Brain Lesions: An Experimental Study

Abstract

An experimental study of the effects of localized cortical lesions on the efficiency and rate of improvement in the performance of a complex motor task was undertaken in 40 patients with verified left and right cerebral hemisphere lesions, and in 20 control subjects. The results show that the right (preferred) hand was superior to the left in the performance of the task in the normal control group and in the patients with left and right cortical lesions. They also indicate that the performance efficiency with both the left and right arm in the control group is superior to that of the patients with left- and right-sided lesions. Normal subjects improved their performance on task repetition with, either the left or the right arm, irrespective of the sequence in which they used the two arms to perform the test (i.e. right arm starting before left or vice versa). In the patients with right-sided cortical lesions no practice improvement occurred when either the left or the right arm was used first in the testing sequence, but significant improvement was obtained when the right arm was tested after the left, and vice versa. Patients with left-sided cortical lesions showed improvement on task repetition, on the whole. The overall performance efficiency with the right arm by normal subjects is decreased when training has been carried out previously with the left arm. On the other hand, this does not apply when the left arm is tested after the right. In patients with right- and left-sided cortical lesions, the overall performance with either arm is uninfluenced by the sequence in which the two arms are used. Finally, the results indicate that the highest percentage of abnormal scores in the performance of the task is obtained by patients with frontal lobe lesions. Some theoretical interpretations of the findings are discussed.