Corticostriatal cells in comparison with pyramidal tract neurons: contrasting properties in the behaving monkey.

Antidromically identified neurons projecting to the putamen (CPNs) and pyramidal tract neurons (PTNs) were recorded from motor and premotor cortex of a monkey which performed a load-bearing task with the wrist. CPNs appeared as a uniform population with very slowly conducting axons and low spontaneous activity. In contrast to PTNs, they exhibited weak, mostly insignificant correlation with graded steady-state forces, responded to torque perturbations with remarkably long latency, and seemed to discharge much later with active movement. Collateral branching of PTNs to the putamen was found to be infrequent (1%). We suggest that the putamen receives a cortical message that is strikingly different from that sent down the pyramidal tract.