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Elizabeth Torres, Christopher Buneo, Richard Andersen; Coding of curved hand paths in the Parietal Reach Region. Journal of Vision 2010;10(7):1091. doi: https://doi.org/10.1167/10.7.1091.
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© ARVO (1962-2015); The Authors (2016-present)
The posterior parietal cortex is an interface between perception and intentional actions (3) demonstrated with the memory-guided reach paradigm. Often the typical PRR neuron responds to visual targets briefly flashed in the dark, sustains the activity during the planning period, and has another firing burst with the initiation of the reach. These responses are gain-modulated by arm position yet the tuning remains throughout the planning period. Such planning-activity patterns suggest a representation of the reach goal indicating the direction of a straight reach from the initial position of the hand to the distal target. It is at present unknown (1) whether this planning code would change when the path to the distal target is not straight, and/or (2) whether this code exclusively represents the goal of the reach. We addressed the first question by interposing physical obstacles on the way to some targets to evoke curved hand paths and necessarily elicit an initial rotation of the hand-target movement vector. To address the second question we placed the obstacle outside of the cells' memory response field and compared its memory activity to the first case, in which the obstacle was placed near the cell's response field. We found systematically in 95 cells from two monkeys a transient remapping and re-scaling of the cells' -response fields during the planning of obstacle-avoidance. Furthermore, these dramatic changes occurred whether or not the obstacle fell near the center of the memory-response field, and despite identical retinal input in the dark (i.e. the fixation light and the target in the periphery). These PRR cells transiently maintained a curved hand path code, and returned back to their original response fields when planning straight reaches again.
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