Activities of neurons in area 3a of the cerebral cortex during voluntary movements in the monkey.

Abstract Neurons in the area 3a of the sensory cortex are known to receive inputs from group I afferent fibers arising from the muscle. The discharge pattern of these neurons during trained wrist movements was studied in the monkey and the following results were obtained. (1) About half of the neurons which received inputs from group I afferent fibers arising from wrist flexors increased their discharges during the shortening phase of the muscle from which the impulses originated. (2) About half of the neurons which received inputs from wrist flexors behaved in the opposite way, i.e. they increased discharges during the lengthening phase of the muscle. (3) A small group of neurons increased discharges during both phases of movements. (4) Possible functional significance of the afferent inputs was discussed in relation to the responsible receptors for these inputs.