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Patrizia Fattori, Rossella Breveglieri, Nicoletta Marzocchi, Passarelli Laura, Claudio Galletti; Monkey area V6A codes reaching movements in the three dimensional peripersonal space. Journal of Vision 2005;5(8):630. doi: 10.1167/5.8.630.
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© ARVO (1962-2015); The Authors (2016-present)
We used a 3-D reaching task to reproduce the spontaneous reaching movements performed by primates in every day life. We recorded neural activity from the medial parieto-occipital cortex (area V6A), while two monkeys performed a three dimensional instructed-delay reaching task in darkness. The animals reached a small target starting from a button placed near the chest. The target to be reached out could be in one of several positions in the peripersonal space. After arm holding on these positions, the animals had to bring their hand back toward the body, to reach the memorized position of the home button.
The present study demonstrates that many V6A neurons are spatially tuned by arm movements aimed at reaching gazed objects placed in the peripersonal space ( 57/150, 38%), and also by movements starting from different spatial locations and directed toward objects placed near the body, outside the field of view ( 61/150, 41%). Several V6A cells (52/150, 35%) are also able to encode the position of the hand in space. A consistent number of cells are involved in more than one epoch during the task. V6A population in the whole codes all the tested directions of reaching. Modulations during reaching execution occurr in V6A in the absence of any visual feedback and are not due to eye movements. The study of neural discharge latency allowed us to discard the hypothesis of a reafferent signal as the only possible source of reach-related modulations, and suggests a corollary discharge from dorsal premotor cortex as one of the sources of reaching modulation in this area.
We suggest that the visuomotor area V6A plays a key role in updating an internal representation of the external world as well as the status of the upper limbs which interact with it, in order to monitor and/or control goal-directed voluntary arm movements.
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