Involvement of aSPOC in the Online Updating of Reach-to-Grasp to Mechanical Perturbations of Hand Transport

Humans adjust their movement to changing environments effortlessly via multisensory integration of the effector's state, motor commands, and sensory feedback. It is postulated that frontoparietal (FP) networks are involved in the control of prehension, with dorsomedial (DM) and dorsolateral (DL) regions processing the reach and the grasp, respectively. This study tested (five female and five male participants) the differential involvement of FP nodes [ventral premotor cortex (PMv), dorsal premotor cortex (PMd), anterior intraparietal sulcus (aIPS), and anterior superior parieto-occipital cortex (aSPOC)] in online adjustments of reach-to-grasp coordination to mechanical perturbations (MP) that disrupted arm transport. We used event-related transcranial magnetic stimulation (TMS) to test whether the nodes of these pathways causally contribute to the processing of proprioceptive information when reaching for a virtual visual target at two different perturbation latencies. TMS over aSPOC selectively altered the correction magnitude of arm transport during late perturbations, demonstrating that aSPOC processes proprioceptive inputs related to mechanical perturbations in a movement phase-dependent manner.