title: Vision for Prehension in the Medial Parietal Cortex.
abstract: In the last 2 decades, the medial posterior parietal area V6A has been extensively studied in awake macaque monkeys for visual and somatosensory properties and for its involvement in encoding of spatial parameters for reaching, including arm movement direction and amplitude. This area also contains populations of neurons sensitive to grasping movements, such as wrist orientation and grip formation. Recent work has shown that V6A neurons also encode the shape of graspable objects and their affordance. In other words, V6A seems to encode object visual properties specifically for the purpose of action, in a dynamic sequence of visuomotor transformations that evolve in the course of reach-to-grasp action.We propose a model of cortical circuitry controlling reach-to-grasp actions, in which V6A acts as a comparator that monitors differences between current and desired hand positions and configurations. This error signal could be used to continuously update the motor output, and to correct reach direction, hand orientation, and/or grip aperture as required during the act of prehension.In contrast to the generally accepted view that the dorsomedial component of the dorsal visual stream encodes reaching, but not grasping, the functional properties of V6A neurons strongly suggest the view that this area is involved in encoding all phases of prehension, including grasping.
authors.affiliation: Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Fattori
authors.affiliation: Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy.
authors.forename: Rossella
authors.initials: R
authors.lastname: Breveglieri
authors.affiliation: Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Bosco
authors.affiliation: Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Gamberini
authors.affiliation: Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Galletti
mesh_terms: D000818:Animals; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D010296:Parietal Lobe / Q000502:physiology*; D011323:Primates; D011597:Psychomotor Performance / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*
keywords: dorsal stream; human and nonhuman primates; object grasping; posterior parietal cortex; reaching movements; visuomotor control