[Relation of functional hemisphere asymmetry to motor performance]

Motor prevalence of one upper extremity can be quantitatively expressed by the ratio of the number of performances carried out by one and the other extremity. One-sided prevalence is most markedly manifested at differentiated performances of the distal part of the extremity which require graded rapid changes of position. The competence of the left hemisphere for sequential analysis is presumably the basis of motor prevalence in right-handed persons. In performances of the proximal parts of the upper extremities involving the axial muscles, one-sided motor prevalence is less pronounced. Bilateral innervation of these parts may account for this finding. The motor preference of one lower extremity appears ontogenetically later and coincides mostly with the dominant upper extremity. Study of the relationship between reflex irritability and motor dominance failed to yield unequivocal results. The motorically dominant hemisphere is usually effective in direction dominance of conjugated lateral eye movements; under certain circumstances functional dominance of the right hemisphere is effective in right-handed persons for processing nonverbal sensoric information.