Integration of cerebral and peripheral inputs by interpositus neurons in monkey.

The patterns of convergence of cerebral and peripheral nerve inputs onto interpositus neurons were studied in cebus monkeys. The strongest inputs to interpositus neurons are from motor and somatosensory cortex, with weaker inputs from peripheral nerves and cerebral area 6. The neurons in the anterior portion of interpositus receive cerebral and peripheral inputs primarily representing the hindlimb, while inputs to neurons in the posterior division represent forelimb or mixed forelimb and hindlimb. The hindlimb neurons integrate signals principally from motor cortex, somatosensory cortex, nerves, supplementary motor and medial pre-motor areas, while forelimb neurons receive inputs from motor, somatosensory, lateral premotor cortical areas and nerves. The results from this study are compared with those from studies of interpositus and dentate neurons in cat and monkey in order to determine the role of n. interpositus in movement. It is suggested that the inputs integrated by interpositus neurons are consistent with a role in up-dating skilled movements.