Evidence for chromatic edge detectors in human vision using classification images

Abstract

Edge detection plays an important role in human vision, and although it is clear that there are luminance edge detectors, it is not known whether there are chromatic edge detectors as well. We showed observers a horizontal edge blurred by a Gaussian filter (with widths of σ = 0.1125, 0.225, or 0.45°) embedded in blurred Brown noise. Observers had to choose which of two stimuli contained the edge. Brown noise was used in preference to white noise to reveal localized edge detectors. Edges and noise were defined by either luminance or chromatic contrast (isoluminant L/M and S-cone opponent). Classification image analysis was applied to observer responses. In this analysis, the random components of the stimulus are correlated with observer responses to reveal a template that shows how observers weighted different parts of the stimulus to arrive at their decision. We found classification images for both luminance and isoluminant chromatic stimuli that had shapes very similar to derivatives of Gaussian filters. The widths of these classification images tracked the widths of the edges, but the chromatic edge classification images were wider than the luminance ones. These results are consistent with edge detection filters sensitive to luminance contrast and isoluminant chromatic contrast.

Gradient in spectral and color images: from the Di Zenzo initial construction to a generic proposition

“…The edge maps are very similar for every sensors. These results concur with recent results about the ability of dichromats and trichromats to perceive patterns and gradients [56], or about the relevance of the chromatic content for gradient or edge detection [57,58].…”

“…Evidently, considering rods in the processing would reduce the differences, but in the same time the cones and rods spatial distribution would have to be considered. Such questions are directly related to recent results about the HVS sensitivity to chromatic edge detectors [58]. Of course, lots of questions are induced by these results: the possible correlations between the existing gra-dients from a physical scene assessed by the FVG and the perceived gradient by the human visual system (HVS), or the HSV possibility to consider the inter-channel correlations.…”

Spatial receptive field structure of double-opponent cells in macaque V1

“…Knowing the spatial structure of DO cell RFs is important for understanding their role in image processing. For example, unoriented RFs could contribute to simultaneous color contrast and could be responsible for the well-documented deficiencies in form vision at isoluminance (Gregory, 1977; M. S. Livingstone, & Hubel, D. H., 1987;McIlhagga, 2018;Mullen, 2002). Oriented RFs could contribute to shape-from-shading-the ability to estimate the 3-D shapes of objects from shading cues (Kingdom, 2003;Kunsberg, 2018).…”

Two-dimensional profile of the region of distractors’ influence on visual length judgments

“…Of note, we are fully aware that the proposed quantitative description, because of its extreme simplicity, does not pretend to identify any specific neural mechanism that underlies the illusion occurrence and in its current state offers only directions for further research. At the same time, derivatives of the Gaussian function, as the weighting profiles are common and widely used to describe the properties of neural structures at different levels of the visual system-for example, receptive fields for motion (Young, Lesperance, & Meyer, 2001) and edge detection (Elder & Sachs, 2004;McIlhagga & Mullen, 2018) or for automatic centroid extraction (Bulatov, Bulatova, Loginovich, & Surkys, 2015). Assuming that during the stimulus observations, gaze fixation is generally tied to the stimulus x-axis (i.e., this axis is located on the visual meridian), the two-dimensional profiles of AWSs can be considered as oriented with their derivative of the Gaussian function along the radial direction in the visual field (and therefore with the Gaussian function located along the tangential direction).…”