ReviewThe Cortical Control of Movement Revisited

Reina et al., 2001). Others suggest that joint angle is Recently, we found that electrical stimulation of motor coded in motor cortex (Scott and Kalaska, 1995, 1997) cortex caused monkeys to make coordinated, comor that muscle tension is coded, perhaps in a complex plex movements. These evoked movements were arfashion in which each location in cortex influences many ranged across the cortex in a map of spatial locations muscles (Evarts, 1968; Cheney et al., 1985; Donoghue to which the hand moved. We suggest that some of et al., 1992; Kakei et al., 1999; Todorov, 2000; Cabel et the subdivisions previously described within primary al., 2001). All of these possibilities have some evidence motor and premotor cortex may represent different in support of them, and the debate has not yet been types of actions that monkeys tend to make in different resolved. Indeed, almost every movement parameter regions of space. According to this view, primary and that has been tested has been found to be encoded by premotor cortex may fit together into a larger map of motor cortex neurons. manual space. (3) The hierarchical organization among the cortical