A map of complex movements in motor cortex of primates
We used electrical microstimulation to study the organization of motor cortex in awake monkeys. Stimulation on a behaviorally relevant time scale (0.5-1 s) evoked coordinated, complex postures that involved many joints. Postures that involved the arm were arranged across cortex to form a map of hand positions around the body. This map encompassed both primary motor and lateral premotor cortex. Primary motor cortex appeared to represent the central part of the workspace, where monkeys most often manipulate objects with their fingers. These findings suggest that primary motor and lateral premotor cortex might not be arranged in a hierarchy, but instead might operate in parallel, serving different behavioral functions in different parts of the workspace. This hypothesis is also consistent with some of the previous data from motor and premotor cortex.