Who tells one hand what the other is doing: the neurophysiology of bimanual movements.

Abstract

Research into neural mechanisms of bimanual coordination sheds light on questions raised by psychophysics. While the results we review are merely suggestive, the overall structure of the neural mechanisms may be emerging slowly.Different mechanisms may serve the spatial and temporal coupling of bimanual movements. Temporal coupling depends on a lateralized pace-keeping mechanism possibly associated with spinal CPGs, is preferentially controlled by the dominant hemisphere, and does not depend directly on the corpus callosum. Spatial coupling, in contrast, arises through interhemispheric interaction. Individual neurons in each hemisphere reflect this interaction, as does interhemispheric synchronization. The interaction allows decoupling of the arms, as substantiated by the PV analysis. Furthermore, bimanual proximal arm movements and finger movements are controlled differently, as shown in differences in the patterns of neural activity in M1 and SMA.Taken as a whole, the research we review has not yet culminated in a conclusive model. However, by combining psychophysics and neurophysiology, we raise concrete, testable hypotheses that may help realize this goal.*To whom correspondence should be addressed (e-mail: eilon@hbf.huji.ac.il).