Motor performance after unilateral hemisphere damage in patients with tumor.

Hemispheric asymmetry of sensory-motor control has been hypothesized on the basis of clinical and experimental data, but discrepant data indicate asymmetry may vary with task requirements. To examine this possibility, the performance of normal controls and patients with right or left hemispheric tumors were compared on a variety of motor tasks of varying complexity. Group differences were significant only for the two most complex of six tasks; since these two tasks differ in quality (proximal steadiness and distal dexterity), it is unlikely that quality differences are crucial. On these tasks, the group with left hemisphere damage demonstrated bilateral impairment while the right hemisphere group's deficits were contralateral to lesion site. These results support previous data and Liepmann's hypothesis of hemispheric asymmetry of sensory-motor control. Task complexity and the more specific hypothesis of sensory-motor sequencing are important factors influencing hemispheric asymmetry of control.