What features of voluntary motor control are encoded in the neuronal discharge of different cortical areas?

Abstract: This chapter reviews evidence concerning the activities of neurons in selected arm-hand motor areas of the cerebral cortex and the parameters of voluntary movement which they appear to encode or control. These multiple motor areas are characterized by somatotopic representation of the arm and hand, by transcortical interconnections, by the presence of direct corticospinal projections to the cervical cord, and by the existence of resident neurons which discharge in relation to various aspects of well-learned, "voluntary" movements. An attempt is made to evaluate semiquantitatively the extent to which cells in these areas discharge in relation to pre-movement instructions, to selection of motor responses, to motor set, or to selected parameters such as movement direction and exerted muscular force. A general summary schema is presented which attempts to depict the location of these brain regions in the central flow of activity which couples environmental stimuli to goal-directed [...]movements. New evidence is also presented concerning the output organization of the precentral (MI) motor cortex, and the implications of these findings as well as others reviewed for future research.