DISTANCE-RELATED AND ERROR-RELATED DISCHARGE OF CELLS IN PREMOTOR CORTEX OF RHESUS-MONKEYS

Previous work on the premotor cortex has emphasized its role in preparation for movement. In this study, we concentrated on the activity that occurs during a movement, particularly when the required movement amplitude is unexpectedly changed by introduction of a visuo-spatial error. In two rhesus monkeys, discharge of premotor neurons was recorded during a multi-joint reaching movement. Units could be divided into two categories: (1) those whose discharge monotonically increased or decreased with movement amplitude; and (2) those whose discharge was modulated with the unexpected change in amplitude but not monotonically. We suggest that the latter class of cells may be detecting or responding to a visuo-motor error. Thus, the premotor cortex is not only involved in preparation but plays a role in the ongoing control of movement execution.