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Christine E. Bredfeldt, Bruce G. Cumming; Orientation tuning for disparity defined edges in Macaque V2. Journal of Vision 2004;4(8):169. https://doi.org/10.1167/4.8.169.
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Although V2 is the primary destination for V1 outputs, and itself provides input to multiple higher processing areas, the characteristics of V2 processing remain largely unknown. Here, we examine how V2 cells process disparity information and whether they may play a role in converting the planar disparity selectivity found in V1 into the more complex disparity tuning seen in higher areas. We focus on the selectivity of V2 cells for disparity defined edges, as edge information can be used for both object definition and scene segmentation. We recorded extracellularly from single units in area V2 of one awake fixating macaque while presenting circular dynamic random dot patterns in which disparity defined a single edge. The orientation of the edge was varied randomly between trials, and during each trial the edge drifted slowly across the receptive field. Each oriented edge could be defined by two disparity signs, depending on which side of the edge was nearer. The stimulus contained no monocular cues to orientation. We found a significant subset of cells that showed orientation dependent tuning for a disparity defined edge (7/48 neurons showed selectivity significant at the 1% level). Some of these neurons were not tuned for the disparity of a planar patch. The edge-selective population includes neurons that respond to only one sign of edge, as well as neurons that respond equally to both signs. We conclude that a subset of V2 cells are involved in developing complex disparity detectors, presumably derived from planar V1 inputs.
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