The posterior parietal cortex supports motor planning and execution through a gradient of neural subspaces

The posterior parietal cortex (PPC) plays a central role in movement control, performing visuomotor transformations, supporting planning, and providing sensory feedback for movement guidance. However, it is unknown how the neural populations in several PPC areas organize their activity during these processes. PPC activity has been proposed to show distributed population dynamics rather than fixed, distinct neural subpopulations dedicated to planning or execution. This raises the question of how the same neural population reconfigures its activity between these two main phases of motor control. To address this, we analyzed neural dynamics in three PPC areas (PE, PEc, V6A) during a delayed reaching task, applying dimensionality reduction methods. This approach identifies whether activity in each area is organized into independent or partially overlapping dynamics across task phases. We found area-specific population subspaces, distinct for movement planning and execution. Specifically, all three areas showed both shared and exclusive subspaces, but cross-epoch coupling and subspace sharing were weaker in PE than in V6A and PEc. Overall, our findings show that different PPC areas balance separate and shared neural activity patterns across movement planning and execution, highlighting distinct contributions to sensorimotor control. In macaque posterior parietal cortex, motor planning and execution are represented by partly shared and distinct neural subspaces, with a posterior to anterior gradient in their coupling.