Laterality of Basic Motor Control Mechanisms: Different Roles of the Right and Left Brain Hemispheres

We present a model of motor lateralization, based in control theory and supported by studies of brain lesions in stroke patients. According to this dynamic dominance model, the hemisphere contralateral to the dominant arm is specialized for predictive control processes that account for the energetics and dynamics of movements, but that depend on the predictability and consistency of the environment. The nondominant system is specialized for impedance control processes that can stabilize performance and reduce errors in the face of unexpected environmental conditions. These complimentary processes across the hemispheres are normally recruited during the use of each arm, but the function of each hemisphere confers its control advantages to the contralateral arm. This scheme is consistent with the work of Rogers and colleagues, who have elaborated a model of brain lateralization that spans a large range of the vertebrate evolutionary spectrum. The complimentary contribution of both brain hemispheres to the control of each arm might explain the greater behavioral symmetry of left-handers, as well as athletes of racquet sports and fencing. In fact, this same phenomenon could account for the slightly higher percentages of left-handers in these sports than the general population.