An Orientation Map for Disparity-Defined Edges in Area V4

Abstract

Binocular disparity information is an important source of 3D perception. Neurons sensitive to binocular disparity are found in almost all major visual areas in nonhuman primates. In area V4, disparity processes are suggested for the purposes of 3D-shape representation and fine disparity perception. However, whether neurons in V4 are sensitive to disparity-defined edges used in shape representation is not clear. Additionally, a functional organization for disparity edges has not been demonstrated so far. With intrinsic signal optical imaging, we studied functional organization for disparity edges in the monkey visual areas V1, V2, and V4. We found that there is an orientation map in V4 activated by edges purely defined by binocular disparity. This map is consistent with the orientation map obtained with regular luminance-defined edges, indicating a cue-invariant edge representation in this area. In contrast, such a map is much weaker in V2 and totally absent in V1. These findings reveal a hierarchical processing of 3D shape along the ventral pathway and the important role that V4 plays in shape-from-disparity detection.

Early Emergence of Solid Shape Coding in Natural and Deep Network Vision

“…AIT neurons typically encode multiple shape motifs in these dimensions, and respond strongly to any object shapes that combine those motifs. 11,12 It has long been thought that solid shape coding emerges only at the end of the ventral pathway, in AIT, 15,16 and that depth information in early and intermediate stages like V4 and PIT, which includes signals for fine-scale and relative depth based on disparity and shading cues, [17][18][19][20][21][22][23][24][25][26] does not extend to robust, explicit signals for shape in depth. 24,27 This would make sense considering the complex computations required for deriving solid shape from 2D images, which might require many processing steps in the ventral pathway network.…”

Impairment of cyclopean surface processing by disparity-defined masking stimuli

“…Instead, such comparisons require measurements based on differences in disparity. Sensitivity to such relative disparities has been noted in multiple areas of cortex (Fang et al, 2018;Neri et al, 2004;Parker, 2007;Thomas et al, 2002;Umeda et al, 2007).…”

“…Studies of the mechanisms responsible for the perception of cyclopean structure have revealed multiple processes, involving the action of multiple neural sites (Neri, 2004;Parker, 2007). Although there is evidence for a progression from absolute disparity selectivity in primary visual cortex to relative disparity selectivity in areas V2 and V4 (Fang et al, 2018;Thomas et al, 2002;Umeda et al, 2007), there is little consensus on either the nature of the transformations involved in this progression, or their computational purpose (cf., Assee & Qian, 2007;Zhaoping, 2002). Tyler (1975Tyler ( , 2012 has suggested a progression from initial disparity measurement units to units with frequency-tuned selectivity for depth sinusoids.…”

“…Beyond these early stages of processing, different response patterns are observed. Beginning at V2, and continuing through multiple cortical sites, neurons show selectivity for relative disparities, that is, for differences between absolute disparity measurements across space (Fang et al, 2018;Neri, Bridge & Heeger, 2004;Thomas, Cumming & Parker, 2002;Umeda, Tanabe & Fujita, 2007). Although sensitivity for relative disparities has not been modeled extensively (cf., Assee & Qian 2007;Zhaoping, 2002), numerous psychophysical observations suggest the importance of processes operating at this level (e.g., Deas & Wilcox, 2014;Deas & Wilcox, 2015;Glennerster & McKee, 1999;Glennerster & McKee, 2004;Goutcher & Hibbard, 2010;Goutcher, Connolly & Hibbard, 2018;Goutcher & Wilcox, 2016;Vreven, McKee & Verghese, 2002;Wardle & Gillam 2016).…”

Curvature domains in V4 of Macaque Monkey

“…However, it is unknown whether such neuronal responses are organized in any way akin to orientation maps in V1 and V2. Previous studies have shown the functional organization of V4 comprises alternating bands of ‘orientation’ and ‘color’ preference (15-17), as well as organization for disparity defined orientation (18), motion direction (16), and spatial frequency (19), but maps for curvature organization have not been demonstrated. Here, we hypothesized that orientation bands in V4 are regions of shape representation that include both orientation and curvature domains.…”