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Carlos R. Ponce, Stephen G. Lomber, Richard T. Born; Contributions of visual areas V2 and V3 to the analysis of depth and motion signals guiding smooth eye movements. Journal of Vision 2006;6(6):4. doi: 10.1167/6.6.4.
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© ARVO (1962-2015); The Authors (2016-present)
The middle temporal (MT) visual area is a critical source of motion and disparity signals used to guide smooth eye movements. It receives major cortical inputs from visual areas V1, V2 and V3, among others. To explore the relative contributions of these inputs, we reversibly inactivated parts of V2 and V3 while measuring smooth eye movements in awake behaving macaques. We implanted three cryogenic loops within the lunate sulcus covering a region approximately 18 mm (medio-lateral) by 8 mm (dorsal-ventral), which allowed us to create a putative V2/V3 scotoma in the contralateral inferior quadrant. Inactivation of this region caused corresponding retinotopic deficits in the initiation of smooth pursuit, short-latency vergence and ocular following responses. These deficits were most pronounced for high stimulus velocities (>30 degrees/s, corresponding to spatial displacements above 0.5 degrees). Vergence was similarly impaired: the only significant changes in horizontal vergence velocity were for eye movements elicited by large binocular disparity steps (> 0.8 degrees). These results suggest that V2 and V3 are important in the processing of visual information used to generate eye movements, contributing most to the analysis of motion signals involving large spatial steps. As directional interactions measured in V1 neurons occur over smaller retinotopic distances (Conway and Livingstone, 2003; Pack et al., in press) the larger receptive fields in V2 and V3 appear to extend the spatial range of visual motion processing.
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