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Patrizia Fattori, Rossella Breveglieri, Nicoletta Marzocchi, Annalisa Bosco, Claudio Galletti; A medial parieto-occipital area coding all phases of prehension movements. Journal of Vision 2008;8(6):373. doi: 10.1167/8.6.373.
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© ARVO (1962-2015); The Authors (2016-present)
In human and monkey posterior parietal cortex (PPC), area AIP is devoted to the guidance of grip formation to grasp an object, area MIP in planning reaching movements in the peripersonal space. Recent fMRI experiments in humans showed an activation of a medial parieto-occipital region for prehension actions. The aim of the present work was to study this region in the monkey brain during all phases of prehension movements. Extracellular recordings were carried out in area V6A of PPC of 2 Macaca fascicularis, performing delayed reach-to-point movements directed to targets located in different positions in the periperonal space and reach-to-grasp movements directed to graspable objects located straight ahead. One hundred V6A neurons were tested in both reach-to-point and reach-to-grasp tasks. We analyzed neural activity during the delay before movement execution, during transport and grasping phases of prehension, hand holding and return movements. About 75% of cells showed different activations in the 2 tasks (point versus grasp). The majority of them (about 60%) showed higher activity during reach-to-grasp rather than during reach-to-point. Of the 34 cells tested for directional tuning of reaching and grip formation, about 40% were able to code both components of prehension. In prehension of objects differently oriented, wrist orientation affected 45% of the neuronal population during planning, 48% during prehension execution, 44% during hand holding and 40% during return movements. These data show that area V6A is involved in all aspects of prehension: in preparing prehension actions, in transporting the arm toward the spatial location of the visual target, in wrist orientation and grip formation till the accomplishement of hand-object interaction. These data suggest the existence in monkey PPC of an area where all aspects of prehension are represented and can address future experiments in the human brain.
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