A quantitative analysis of stimulus- and movement-related responses in the posterior parietal cortex of the monkey.

The posterior parietal cortex (areas 5 and 7) in monkeys has been described as a higher association cortex and as such, area 5 has been attributed a complex somaesthetic function. More recently, a role in the formation of motor commands has been postulated for these two cortical areas. We have been particularly interested in the role area 5 neurons may have in movement initiation. Single neuron activity was recorded in area 5 during the performance of a trained forelimb movement in monkeys and neuronal responses which occurred prior to movement were observed. In the present report, we have examined the neuronal discharge data trial by trial using a technique of data analysis which enabled us to separate the changes in neuronal activity into stimulus- or movement-related responses. Both stimulus- and movement-related responses were identified. The stimulus-related responses were not simple sensory responses since they were also influenced by the timing of the onset of movement. These results suggest that certain area 5 neurons may be involved in the linking of sensory inputs with motor outputs. Cerebrocerebellar loops may be a pathway in this linkage. The latencies of the movement-related responses were such that corollary discharge from the motor cortex may have played a role in this activity. Such corollary discharge may be a form of information used by the animal to execute movement in the absence of peripheral feedback.