An Orientation Map for Motion Boundaries in Macaque V2

Abstract

The ability to extract the shape of moving objects is fundamental to visual perception. However, where such computations are processed in the visual system is unknown. To address this question, we used intrinsic signal optical imaging in awake monkeys to examine cortical response to perceptual contours defined by motion contrast (motion boundaries, MBs). We found that MB stimuli elicit a robust orientation response in area V2. Orientation maps derived from subtraction of orthogonal MB stimuli aligned well with the orientation maps obtained with luminance gratings (LGs). In contrast, area V1 responded well to LGs, but exhibited a much weaker orientation response to MBs. We further show that V2 direction domains respond to motion contrast, which is required in the detection of MB in V2. These results suggest that V2 represents MB information, an important prerequisite for shape recognition and figure-ground segregation.

Curvature domains in V4 of Macaque Monkey

“…4, Case 2; Fig. S11C-D, Case 1), we used 4 orientations of curvature (curved upwards, downwards, leftwards, and rightwards), each at low curvature (1-4) and high curvature (5-8). Similar to maps for straight orientation (Fig.…”

“…For example, each of V1, V2, and V4 contain orientation selective domains; however, orientation selective domains are categorically different in V1, V2, and V4. Whereas those in V1 are responsive to contrast-defined orientation, those in V2 have cue-invariant orientation selectivity and represent a higher order abstraction of orientation (5, 37, 38). We suggest that orientation selective domains in V4 are at yet a higher level.…”

“…Curvature stimuli were designed based on the formula of ellipse, X 2 /a 2 + Y 2 /b 2 = 1, where a and b represent the length of the long axis and short axis respectively. Different a/b ratios were used (2, 5, See Fig. 3B; 1, 4, 7, 10, see Fig.…”

“…The encoding of contour orientation in the visual system begins in primary visual cortex (V1) with neurons selective for the orientation of visual contours, and, in the second visual area (V2), with neurons selective for cue-invariant contour orientation (that is, independent of whether contours are defined by luminance, motion, color, or depth cues). These two functions are first embodied in the ‘ orientation domain ’ in V1 (1-3) and the ‘higher order orientation domain’ in V2 (4-5). These signature domains in V1 and V2 mark initial computational elements of shape representation.…”

Specificity of V1–V2 orientation networks in the primate visual cortex

“…Those associated with thin stripes (lying lateral to thin stripes, Type I) do not receive input from layer 4B in V1, exhibit lower orientation selectivity and greater color selectivity, larger receptive size and scatter, and smaller orientation domains and maps with rapidly changing orientation preference. Thick stripes are heterogeneous and contain functional domains selective for ocular disparity (Chen et al 2008), lower and higher order contour orientation selectivity (Ramsden et al, 2001, 2014; Pan et al, 2012; Chen et al, 2014), and motion contrast borders (Lu et al 2010; Chen et al 2014). They have direct projections to MT (DeYoe & Van Essen, 1985; Shipp & Zeki, 1985, 1989; Born & Bradley, 2005) and likely indirect projections to V4 (Ninomiya et al, 2011), and thus have strong ties with both the dorsal and ventral pathways.…”