Anterior-posterior gradient in the integrated processing of forelimb movement direction and distance in macaque parietal cortex

A major issue in modern neuroscience is to understand how cell populations present multiple spatial and motor features during goal-directed movements. The direction and distance (depth) of arm movements often appear to be controlled independently during behavior, but it is unknown whether they share neural resources or not. Using information theory, singular value decomposition, and dimensionality reduction methods, we compare direction and depth effects and their convergence across three parietal areas during an arm movement task. All methods show a stronger direction effect during early movement preparation, whereas depth signals prevail during movement execution. Going from anterior to posterior sectors, we report an increased number of cells processing both signals and stronger depth effects. These findings suggest a serial direction and depth processing consistent with behavioral evidence and reveal a gradient of joint versus independent control of these features in parietal cortex that supports its role in sensorimotor transformations.