Intermanual differences on skilled and unskilled motor tasks in nonlateralized brain dysfunction

Intermanual (right-left) comparison of motor and perceptual performances is an essential method of interpretation in clinical neuropsychology. Relatively deficient performance with one hand suggests contralateral hemispheric dysfunction. There could, however, be another reason for comparatively poor performance of the nonpreferred hand. If one assumes a greater adaptive component for performance with the non-preferred (less practiced) hand on certain motor tasks, nonlateralized brain dysfunction could result in greater decrement for the nonpreferred hand. It was hypothesized that for Finger Tapping, Grooved Pegboard, and Television Writing Time (but not for Hand Dynamometer) intermanual differences favoring the preferred hand would be greater for epileptic patients with nonlateralized brain dysfunction than for controls. The hypothesis was supported, and the clinical implications are discussed.