Handedness, footedness and finger and toe movement-related cerebral potentials.

Sixteen right-handed and 16 left-handed subjects were compared with respect to their foot dominance and the topography of their pre-movement cerebral potentials (Bereitschaftspotential, BP). First, righthanders were usually also found to be right-footed. Lefthanders showed a similar trend in preferring their left foot. Second, the BP prior to volitional self-paced movements of fingers and toes on either side was examined. For finger movements, the BP always showed higher amplitudes over the contralateral hemisphere as compared to the ipsilateral one (contralateral preponderance of negativity, CPN). For toe movements a significant ipsilateral preponderance of negativity (IPN) occurred in all subjects. The CPN was larger for finger movements of the dominant hand than it was for finger movements on the non-dominant side. By contrast, the IPN was larger prior to movements of the "non-dominant toes" than it was for movements of the dominant toes. This can be explained by assuming that the hemisphere contralateral to the dominant hand, generates more negativity than the one contralateral to the non-dominant hand. This assumption is further discussed in the context of a vector model for the BP.