Decoding continuous and discrete motor behaviors using motor and premotor cortical ensembles.

Decoding motor behavior from neuronal signals has important implications for the development of a brain-machine interface (BMI) but also provides insights into the nature of different movement representations within cortical ensembles. Motor control can be hierarchically characterized as the selection and planning of discrete movement classes and/or postures followed by the execution of continuous limb trajectories. Based on simultaneous recordings in primary motor (MI) and dorsal premotor (PMd) cortices in behaving monkeys, we demonstrate that an MI ensemble can reconstruct hand or joint trajectory more accurately than an equally sized PMd ensemble. In contrast, PMd can more precisely predict the future occurrence of one of several discrete targets to be reached. This double dissociation suggests that a general-purpose BMI could take advantage of multiple cortical areas to control a wider variety of motor actions. These results also support the hierarchical view that MI ensembles are involved in lower-level movement execution, whereas PMd populations represent the early intention to move to visually presented targets.