Functional specialization of the human posterior parietal cortex in visually and proprioceptively driven reaching corrections.

While online adjustments during reaching are essential for interacting with our dynamic environment, the specialized contributions of subregions of the posterior parietal cortex (PPC) remain unclear. In this study, we investigate the distinct roles of human medial PPC areas V6A (hV6A) and PEc (hPEc) in mediating online reaching corrections elicited by visual and proprioceptive perturbations. Here we deliver online repetitive transcranial magnetic stimulation (rTMS) during the early stages of reaching corrections triggered by an unexpected shift of the visual target or by the application of an external force to the wrist. Our findings reveal that rTMS over hV6A selectively impairs the ability to correct reach trajectories for visual perturbations, whereas stimulation of hPEc interferes only with proprioceptively driven corrections. These findings confirm the critical role of hV6A in processing visual feedback, demonstrate the causal involvement of hPEc in integrating proprioceptive information to guide motor adjustments, and show how the PPC selectively engages specialized neural circuits to adapt motor control strategies according to the sensory nature of the reaching perturbation.