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A. R. Dickinson, J. L. Calton, L. H. Snyder; Non-spatial motor-specific activations of two distinct regions of posterior parietal cortex (PPC). Journal of Vision 2001;1(3):234. doi: 10.1167/1.3.234.
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Cells in PPC are involved in goal-directed eye and arm movements to visible targets. We quantified the neural response to cueing the spatial goal of a movement (“spatial information”) versus cueing only the motor effector (eye or arm: “task information”). We previously reported that the parietal reach region (PRR) could be driven by task information in the complete absence of spatial information. We now report a similar effect for the lateral interparietal area (LIP). In LIP, 44% and 22% of cells (in two animals, respectively) were preferentially activated by plans for eye compared to arm movements. Only 5% and 4% of cells, respectively, showed the reverse preference (arm over eye). Across all cells in LIP, task information without spatial information resulted in 31% and 28% as much activity as spatial information without task information. PRR showed the reverse motor preferences, with 45% and 27% of cells preferentially activated by plans for arm compared to eye movements. Only 10% and 3% of cells preferred eye over arm. Across all PRR cells, task information without spatial information resulted in 37% and 46% as much activity as spatial information without task information. Both areas show clear evidence of substantial non-spatial, but motor-specific activations. Both the percentage of significantly activated cells and the extent of activation are comparable in the two areas, though the effects are slightly stronger in PRR. The dorsal stream, therefore, not only process visuospatial information, but also code effector-specific motor intentions, even in the absence of spatial information.
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