Distinct neural components of visually guided grasping during planning and execution

Abstract

2 Selecting suitable grasps on three-dimensional objects is a challenging visuomotor 3 computation, which involves combining information about an object (e.g., its shape, 4 size, and mass) with information about the actor’s body (e.g., the optimal grasp 5 aperture and hand posture for comfortable manipulation). Here we used functional 6 magnetic resonance imaging to investigate brain networks associated with these 7 distinct aspects during grasp planning and execution. Human participants 8 of either sex viewed and then executed preselected grasps on L-shaped objects 9 made of wood and/or brass. By leveraging a computational approach that accurately 10 predicts human grasp locations, we selected grasp points that disentangled the role 11 of multiple grasp-relevant factors: grasp axis, grasp size, and object mass. 12 Representational Similarity Analysis revealed that grasp axis was encoded along 13 dorsal-stream regions during grasp planning. Grasp size was first encoded in 14 ventral-stream areas during grasp planning, then in premotor regions during grasp 15 execution. Object mass was encoded in ventral-stream and (pre)motor regions only 16 during grasp execution. Premotor regions further encoded visual predictions of grasp 17 comfort, whereas the ventral stream encoded grasp comfort during execution, 18 suggesting its involvement in haptic evaluation. These shifts in neural 19 representations thus capture the sensorimotor transformations that allow humans to 20 grasp objects.