Dissociation of spatial and temporal coupling in the bimanual movements of callosotomy patients

The neural mechanisms of limb coordination were investigated by testing callosotomy patients and normal control subjects on bimanual movements. Normal subjects produced deviations in the trajectories when spatial demands for the two hands were different, despite temporal synchrony in the onset of bimanual movements. Callosotomy patients did not produce spatial deviations, although their hands moved with normal temporal synchrony. Normal subjects but not callosotomy patients exhibited large increases in planning and execution time for movements with different spatial demands for the two hands relative to movements with identical spatial demands for the two hands. This neural dissociation indicates that spatial interference in movements results from callosal connections, whereas temporal synchrony in movement onset does not rely on the corpus callosum.