Although it is well known that the major input to the stratium originates in the cerebral cortex, virtually nothing is known about the type of information conveyed by the corticostriatal pathway. The part of the striatum that receives input from the primary motor cortex is the putamen. Putamen neurons discharge at or after the onset of EMG activity and reflect the direction of movement per se, whereas many neurons in the primary motor cortex discharge prior to the onset of EMG activity and reflect individual muscle activity independent of the direction of movement. To investigate corticostriatal (CS) activity during movement, we developed a strategy to identify CS neurons and quantitate their activity, their timing with respect to movement, and their relationship to the pattern of muscle activation in rhesus monkeys. Our observations indicate that motor information is conveyed via neurons than putamen neurons with respect to their timing and relationship to the patterns of muscle activity. It is possible, therefore, that motor disorders could result from excess in CS activity that causes abnormal contraction of muscles and limb position in space.
