Representation of 3-D surface orientation by velocity and disparity gradient cues in area MT

Abstract

Sanada TM, Nguyenkim JD, DeAngelis GC. Representation of 3-D surface orientation by velocity and disparity gradient cues in area MT. J Neurophysiol 107: 2109 -2122, 2012. First published January 4, 2012; doi:10.1152/jn.00578.2011.-Neural coding of the threedimensional (3-D) orientation of planar surface patches may be an important intermediate step in constructing representations of complex 3-D surface structure. Spatial gradients of binocular disparity, image velocity, and texture provide potent cues to the 3-D orientation (tilt and slant) of planar surfaces. Previous studies have described neurons in both dorsal and ventral stream areas that are selective for surface tilt based on one or more of these gradient cues. However, relatively little is known about whether single neurons provide consistent information about surface orientation from multiple gradient cues. Moreover, it is unclear how neural responses to combinations of surface orientation cues are related to responses to the individual cues. We measured responses of middle temporal (MT) neurons to random dot stimuli that simulated planar surfaces at a variety of tilts and slants. Four cue conditions were tested: disparity, velocity, and texture gradients alone, as well as all three gradient cues combined. Many neurons showed robust tuning for surface tilt based on disparity and velocity gradients, with relatively little selectivity for texture gradients. Some neurons showed consistent tilt preferences for disparity and velocity cues, whereas others showed large discrepancies. Responses to the combined stimulus were generally well described as a weighted linear sum of responses to the individual cues, even when disparity and velocity preferences were discrepant. These findings suggest that area MT contains a rudimentary representation of 3-D surface orientation based on multiple cues, with single neurons implementing a simple cue integration rule. depth; slant; surface; tilt; visual cortex; middle temporal area THE VISUAL SYSTEM RECONSTRUCTS three-dimensional (3-D) scene structure from images projected onto the two retinas. Many cues, including binocular disparity, relative motion, texture, shading, and perspective, are used to perceive 3-D structure. Most complex surfaces can be approximated by combinations of locally planar surfaces. Thus understanding how planar surfaces are coded in visual cortex may help reveal how complex surface representations are constructed. The 3-D orientation of a plane (tilt and slant) can be specified by gradients of binocular disparity, motion (velocity), or texture. Human perception of 3-D surface orientation from these cues has been well studied, and the findings are often well explained by Bayesian models (Girshick and Banks 2009;Hillis et al. 2004;Jacobs 1999;Knill 2007;Knill and Saunders 2003).Physiological studies in macaques have identified neurons that signal the 3-D orientation of planar surfaces. In the ventral stream, 3-D orientation tuning has been reported in area V4 for disparity gradients (Hegde and Van Ess...

Reliability-dependent contributions of visual orientation cues in parietal cortex

“…S4). Given this result, the finding that tilt-selective middle temporal neurons have weak texture sensitivity may, in part, reflect that the stimuli were presented binocularly (10). The present findings are also consistent with the sensation of depth being stronger when a texture stimulus (e.g., a painting with perspective) is viewed monocularly rather than binocularly (22), reflecting the elimination of the cue conflict occurring when pictorial depth cues are viewed binocularly.…”

“…In previous studies examining neuronal sensitivity to 3D orientation cues, either the texture-defined and disparity-defined slants could not be equated (9) or the texture stimuli were only presented binocularly (7,8,10). In contrast, we rendered the stimuli such that the texture-defined and disparity-defined slants were equivalent, and presented texture stimuli monocularly and binocularly.…”

“…Multiple signals, including texture (available monocularly) and binocular disparity, are used to determine 3D orientation (5,6). Single-unit (7)(8)(9)(10) and functional MRI (fMRI) (11)(12)(13) studies indicate that different orientation cues are combined in high-level cortical areas.…”

Choice-Related Activity during Visual Slant Discrimination in Macaque CIP but Not V3A

“…During pilot work, we observed that local orientation cues in checkerboard stimuli could 10 be used to perform the task without having to judge slant. To avoid this potential confound, the 11 discrimination task was performed using RDS planes with uniform dot density on the screen 12 (Sanada et al, 2012). In CIP, slant tuning curves measured with planar surfaces with a 13 checkerboard pattern or a random dot pattern are highly correlated (Rosenberg and Angelaki, 14 2014b).…”

The lawful imprecision of human surface tilt estimation in natural scenes

“…Numerous psychophysical, computational, and neurophysiological studies have probed the human ability to estimate surface slant, surface tilt, and 3D shape [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Lawful performance has been observed and models have been developed that nicely describe performance.…”