Functional organization of the human primary motor area: an update on current concepts.

Studies on the functional mapping of the human primary motor cortex (MI) are reviewed. In human subjects, the MI has been generally recognized as the cortical executive locus for all voluntary movements. However, some investigators have reported that activity in the MI is related to ipsilateral distal limb movements, and that the MI hand area contains subregions which are related to preparatory activity and subregions which change their activity with the learning of new motor skills. These recent findings challenge the traditional concepts of the functional role of the MI.