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P. Janssen, R. Vogels, Y. Liu, G. A. Orban; The representation of vertical and horizontal disparity gradients in macaque inferior temporal cortex. Journal of Vision 2001;1(3):275. doi: 10.1167/1.3.275.
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The rostral lower bank of the Superior Temporal Sulcus (TEs), part of the inferior temporal cortex, contains neurons selective for disparity-defined 3D shapes [Janssen et al. (2000). Science 288, 2054]. In the previous experiments, all 3D shapes were curved only along the vertical axis. To determine the selectivity for disparity variations along the horizontal axis, we recorded the responses of single neurons to concave and convex 3D shapes in which surface and boundary were curved in depth either along the vertical axis or along the horizontal axis. Additionally, the neurons were tested with a 3D surface in which the disparity was maximal in the center of the shape and smoothly approached zero towards the boundaries along both the vertical and the horizontal axis. After a preliminary test with monocular presentations and a position-in-depth test demonstrating 3D shape-selectivity, 46 neurons were tested in detail. Fifty-four percent of the neurons tested (25/46) responded selectively to the vertical disparity gradients, whereas 37% (17/46) of the neurons tested were selective to the horizontal variation of disparity and 63% (29/46) of the neurons responded selectively to the surface containing both a vertical and a horizontal gradient. Of the 25 “vertical” neurons, 20 (80%) were not selective for the horizontal gradient, while 12 out of 17 “horizontal” neurons (71%) were not selective for the vertical gradient. Further tests with uncorrelated stimuli showed that boundary disparities along the vertical axis, but not along the horizontal axis, can be sufficient for 3D shape-selectivity. Thus, TEs neurons are selective for vertical and horizontal disparity variations, which suggests coding of the direction of curvature.
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