Distance- 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.