Authors: Theys, Tom
Issue Date: 31-May-2012
Abstract: Using single cell recordings in non-human primates we tried to obtain a better insight in the neurophysiology of visuomotor processing for the purpose of grasping. Since binocular disparity is the main depth cue for the control of our grasp, the neural representation of disparity-defined curved surfaces can be important for the intricate visuomotor transformations necessary for visually-guided grasping. We studied the representation of 3D shape in posterior parietal area AIP and ventral premotor area F5a, two brain areas known to be critically involved in grasping. In area AIP, an end-stage area of the dorsal visual stream, neurons mainly process 3D object boundary information with a strong emphasis on the axis of curvature. These neurons have a fast and coarse representation of depth information and are insensitive to anticorrelated disparities. Recording sites in area AIP, involved in 3D shape processing, were also responsive during visually guided grasping. These findings are consistent with the view that the dorsal stream is selectively important for using visual information to guide actions.In area F5a, neurons showed similar robust 3D-shape selectivity in the absence of a motor response. The neuronal 3D shape coding was very similar to area AIP with a rather coarse and monotonous coding. This metric coding is probably important for the fine control of hand movements towards objects. Disparity selective F5a neurons frequently exhibited responses during grasping of real-world objects. 3D-shape selective single units responsive during grasping were generally visual and nearby neurons often showed motor-related activity in the dark. Such neurons were only found in a specific anatomical subsector of F5, not in surrounding periarcuate areas. This peculiar area is therefore distinct from neighboring regions of the ventral premotor cortex, in line with anatomical connectivity studies. This three-dimensional shape selectivity in the parietofrontal grasping circuit suggests a pivotal role in the intricate process of visuomotor transformations for grasping. The rapid and accurate 3D-shape processing can hereby guide the preshaping of the hand according to particular 3D object properties.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Research Group Neurophysiology
Research Group Experimental Neurosurgery and Neuroanatomy

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