V3A Processes Contour Curvature as a Trackable Feature for the Perception of Rotational Motion

Caplovitz, Gideon P.; Tse, Peter U.

doi:10.1093/cercor/bhl029

Cited by 52 publications

(45 citation statements)

References 71 publications

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“…1 When the stimulus changes from the local to the global percept, it appears to move more slowly, even though the dots themselves never change speed at the level of the stimulus. This implies that the perceived speed of the global-motion percept is not determined solely by the local speeds of the individual dots, which is consistent with the view that motion is computed in light of the outputs of a stage of form analysis (Ames, 1951;Caplovitz & Tse, 2007a, 2007bKlopfer, 1991;Lorenceau & Shiffrar, 1992;Shiffrar, Li, & Lorenceau, 1995;Sinha & Poggio, 1996;Tse, 2006;Tse & Logothetis, 2002;Ullman, 1979). In the present article, we describe two psychophysical experiments that further examined the influence of perceived form on perceived motion.…”

supporting

confidence: 73%

“…The global percept here may be seen to move more slowly because of an increase in speed-discrimination threshold, which is caused by the parsing of the Ls into two large squares in the global be determined solely on the basis of local speed-tuned mechanisms. Rather, motion appears to be computed in light of input from a global analysis that interpolates forms such as the virtual squares that were perceived in the global configuration (Ames, 1951;, 2007a, 2007bKlopfer, 1991;Lorenceau & Shiffrar, 1992;Shiffrar et al, 1995;Sinha & Poggio, 1996;Tse, 2006;Tse & Logothetis, 2002;Ullman, 1979). Instantaneous motion vectors must be computed in light of the outputs of such nonlocal grouping or segmentation operations.…”

Section: Discussionmentioning

confidence: 99%

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The whole moves less than the spin of its parts

Kohler

Caplovitz²,

Tse

2009

Attention, Perception, & Psychophysics

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It is often said that the whole is greater than the sum of its parts. Is this true for motion perception? Can a global-motion percept appear to be faster or slower than the sum of local-motion inputs from which it derives? For example, when four pairs of dots are rotated continuously around their respective pair centers, as is shown in Figure 1, the percept alternates between one of four independently rotating dot pairs (local motion) and one of two overlapping squares that have dots at their corners and that appear to translate along overlapping circular trajectories (global motion;Anstis, 2003). 1 When the stimulus changes from the local to the global percept, it appears to move more slowly, even though the dots themselves never change speed at the level of the stimulus. This implies that the perceived speed of the global-motion percept is not determined solely by the local speeds of the individual dots, which is consistent with the view that motion is computed in light of the outputs of a stage of form analysis (Ames, 1951;Caplovitz & Tse, 2007a, 2007bKlopfer, 1991;Lorenceau & Shiffrar, 1992;Shiffrar, Li, & Lorenceau, 1995;Sinha & Poggio, 1996;Tse, 2006;Tse & Logothetis, 2002;Ullman, 1979). In the present article, we describe two psychophysical experiments that further examined the influence of perceived form on perceived motion. METHODTo investigate this "motion slowdown" effect, we effectively forced a local or global perceptual organization, rather than relying on the uncontrollable perceptual alternations that occur while one is viewing the original dot version of this stimulus (Anstis, 2003). To achieve this, we replaced each dot with an L-shaped stimulus (hereafter, "L"). 2 In the global stimulus configuration, the Ls were oriented to align in such a manner that they would consistently induce the global percept (shown on the left side of Figure 2). In the local configuration, the orientations of the Ls were chosen pseudorandomly, so as to induce the local percept of four independently rotating pairs.To further bias this configuration toward the local percept, the starting orientation of each pair was randomized on every trial (right side of Figure 2). We thus created two versions of the stimulus that, although almost identical at the local level (observing the motion of only a single L would not reveal whether one was observing the local or global configuration), were radically different in their ability to induce the global percept.Stimuli were white (67.02 cd/m 2 ) on a gray (4.09 cd/m 2 ) background, with a white (67.02 cd/m 2 ) vertical bar separating the two sides of the display. The two line segments that constituted each L measured 0.5º of visual angle in length. Within a pair, the distance between Ls measured 0.8º (see Figure 2). The vertical distance between pairs was 3º, and the horizontal distance between pairs was 4º. Each stimulus configuration was centered 6.84º from the fixation spot. While maintaining central fixation, observers reported that they could easily see all the moving elements...

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supporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

The whole moves less than the spin of its parts

Kohler

Caplovitz²,

Tse

2009

Attention, Perception, & Psychophysics

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“…It is involved in the processing of 3D visual information about objects in space (52). Apart from motion, it responds to both monocular (22) and binocular (53,54) depth information and has strong projections to the lateral intraparietal area (LIP) and anterior intraparietal area within PPC, which process visual 3D object information and object-related hand actions (55).…”

Section: Functional Contribution Of V6mentioning

confidence: 99%

Adjacent visual representations of self-motion in different reference frames

Arnoldussen

Goossens²,

Berg³

2011

Proc. Natl. Acad. Sci. U.S.A.

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Recent investigations indicate that retinal motion is not directly available for perception when moving around [Souman JL, et al. (2010) J Vis 10:14], possibly pointing to suppression of retinal speed sensitivity in motion areas. Here, we investigated the distribution of retinocentric and head-centric representations of selfrotation in human lower-tier visual motion areas. Functional MRI responses were measured to a set of visual self-motion stimuli with different levels of simulated gaze and simulated head rotation. A parametric generalized linear model analysis of the blood oxygen level-dependent responses revealed subregions of accessory V3 area, V6 + area, middle temporal area, and medial superior temporal area that were specifically modulated by the speed of the rotational flow relative to the eye and head. Pursuit signals, which link the two reference frames, were also identified in these areas. To our knowledge, these results are the first demonstration of multiple visual representations of self-motion in these areas. The existence of such adjacent representations points to early transformations of the reference frame for visual self-motion signals and a topography by visual reference frame in lower-order motion-sensitive areas. This suggests that visual decisions for action and perception may take into account retinal and head-centric motion signals according to task requirements.hen a child eyeballs the seeker while exposing as little as possible of its head from behind cover, it performs an exquisite piece of eye and head control. Such visually coordinated actions rely on fast and dynamic integration of selfmotion signals from different reference frames (1) to control the rotations of the head, the eye, and other body parts.Motion relative to the eye is directly given on the retina. In the monkey lower-tier visual areas, neurons respond vigorously to such retinal motion (2, 3). Motion relative to the head or other body parts must be derived from visual (4) and nonvisual (5) information on the eye's rotation (6). Many monkey cortical areas also contain neurons that take into account the eye's rotation when responding to visual motion (7-10). Remarkably, a number of recent psychophysical studies have concluded that retinal motion signals are not directly available for perception (11-13), in particular during self-motion (11), whereas headcentric motion signals are.This raises the interesting question how retinal and headcentric representations of visual motion are distributed across the lower-tier visual motion areas. If subjects cannot attend to retinal motion signals, it could indicate that retinal motion sensitivity gives way to head-centric motion signals in higher tier areas, such as the posterior parietal cortex (PPC). Alternatively, signals in both reference frames may be present up to higher visual areas, but not available for certain visual tasks or under certain movement conditions. We investigated if the visual system builds up visual representations of eye-in-space and head-in-space motion. T...

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“…Cortical area V3A is one possible brain area where such surface contour signals may get converted into eye movement target signals. In particular, studies show that it is concerned with relative disparity (Backus, Fleet, Parker & Heeger, 2001), gaze (Galletti & Battaglini, 1989), saccades (Caplovitz & Tse, 2006, Nakamura & Colby, 2000 and prehensile hand movements (Nakamura, et al, 2001). This proposal is offered tentatively due to the sparcity of available data, combined with evidence that the function of macaque V3A differs from that performed by human V3A (Tootell, et al, 1997).…”

Section: Shrouds Coordinate Scanning Eye Movements and Object Categormentioning

confidence: 99%