A posture subspace in the primary motor cortex

To generate movements, the brain must combine information about movement goal and body posture. The motor cortex (primary motor cortex [M1]) is a key node for the convergence of these information streams. How are posture and goal signals organized within M1's activity to permit the flexible generation of movement commands? To answer this question, we recorded M1 activity while monkeys performed a variety of tasks with the forearm in a range of postures. We found that posture- and goal-related components of neural population activity were separable and resided in nearly orthogonal subspaces. The posture subspace was stable across tasks. Within each task, neural trajectories for each goal had similar shapes across postures. Our results reveal a simpler organization of posture signals in M1 than previously recognized. The compartmentalization of posture and goal signals might allow the two to be flexibly combined in the service of our broad repertoire of actions.