Three-dimensional shape coding in grasping circuits: a comparison between the Anterior Intraparietal area and ventral premotor area F5a

Depth information is necessary for adjusting the hand to the three-dimensional shape of an object in order to grasp it. The transformation of visual information into appropriate distal motor commands is critically dependent on the Anterior IntraParietal area (AIP) and the ventral premotor cortex (area F5), particularly the F5p sector. Recent studies have demonstrated that both AIP and the F5a sector of the ventral premotor cortex contain neurons that respond selectively to disparity-defined three-dimensional (3D) shape. To investigate the neural coding of 3D shape and the behavioral role of 3D-shape selective neurons in these two areas, we recorded single-cell activity in AIP and F5a during passive fixation of curved surfaces and during grasping of real-world objects.Similar to those in AIP, F5a neurons were either first- or second-order disparity selective, frequently showed selectivity for discrete approximations of smoothly-curved surfaces that contained disparity discontinuities, and exhibited mostly monotonic tuning for the degree of disparity variation. Furthermore, in both areas, 3D-shape selective neurons were co-localized with neurons that were active during grasping of real-world objects. Thus area AIP and F5a contain highly similar representations of 3D shape, which is consistent with the proposed transfer of object information from AIP to the motor system through the ventral premotor cortex.status: publishe