Coherent Compound Motion: Corners and Nonrigid Configurations

Consider two wire gratings, superimposed and moving across each other. Under certain conditions the two gratings will cohere into a single, compound pattern, which will appear to be moving in another direction. Such coherent motion patterns have been studied for sinusoidal component gratings, and give rise to percepts of rigid, planar motions. In this paper we show how to construct coherent motion displays that give rise to nonuniform, nonrigid, and nonplanar percepts. Most significantly, they also can define percepts with corners. Since these patterns are more consistent with the structure of natural scenes than rigid sinusoidal gratings, they stand as interesting stimuli for both computational and physiological studies. To illustrate, our display with sharp corners (tangent discontinuities or singularities) separating regions of coherent motion suggests that smoothing does not cross tangent discontinuities, a point that argues against existing (regularization) algorithms for computing motion. This leads us to consider how singularities can be confronted directly within optical flow computations, and we conclude with two hypotheses: (1) that singularities are represented within the motion system as multiple directions at the same retinotopic location; and (2) for component gratings to cohere, they must be at the same depth from the viewer. Both hypotheses have implications for the neural computation of coherent motion.

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Natural-Image Discrimination in the Periphery: The Importance of Phase and Amplitude Information

Perception ◽

10.1068/v96l1006 ◽

1996 ◽

Vol 25 (1_suppl) ◽

pp. 85-85

Author(s):

G M Kennedy ◽

D J Tolhurst

Keyword(s):

Phase Change ◽

Scaling Factor ◽

Natural Images ◽

Natural Image ◽

Rapid Decline ◽

Natural Scenes ◽

Phase Identification ◽

Phase Information ◽

Black And White ◽

Sinusoidal Gratings

Previous studies with simplified stimuli such as combinations of sinusoidal gratings have revealed phase identification losses in the periphery that are not eliminated by a scaling factor. How do these phase processing problems influence our ability to discriminate natural images in the periphery? In this study the ability of an observer to identify the ‘odd-image-out’ when there is either an amplitude-only, phase-only, or amplitude and phase change in one out of three stimuli is compared. Pairs of Fourier-manipulated black-and-white digitised photographs of natural images were used and phase and amplitude spectral exchanges of varying proportions were made between two different images. Measurements were made to determine the smallest phase change needed in order for the observer to reliably discriminate the manipulated image, compared to two reference stimuli, at eccentricities of 0°, 2.5°, 5°, and 10°. This was compared to discrimination thresholds found when amplitude and phase, and amplitude alone were exchanged. The ability to discriminate images on the basis of phase information alone did fall off quickly with eccentricity (comparable to phase and amplitude discriminations). However, there was a much more rapid decline in amplitude-only discrimination. It appears that phase information in natural scenes remains a relatively more important visual cue in the periphery than amplitude.

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Exploring Coherent Motion Patterns via Structured Trajectory Learning for Crowd Mood Modeling

IEEE Transactions on Circuits and Systems for Video Technology ◽

10.1109/tcsvt.2016.2593609 ◽

2017 ◽

Vol 27 (3) ◽

pp. 635-648 ◽

Cited By ~ 11

Author(s):

Yanhao Zhang ◽

Lei Qin ◽

Rongrong Ji ◽

Sicheng Zhao ◽

Qingming Huang ◽

...

Keyword(s):

Coherent Motion ◽

Motion Patterns ◽

Trajectory Learning

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Brain stem and cortical contributions to the generation of horizontal optokinetic eye movements in humans

Visual Neuroscience ◽

10.1017/s0952523800003655 ◽

1993 ◽

Vol 10 (2) ◽

pp. 247-259 ◽

Cited By ~ 13

Author(s):

Laurence R. Harris ◽

Terri L. Lewis ◽

Daphne Maurer

Keyword(s):

Eye Movements ◽

Brain Stem ◽

Eye Movement ◽

Monocular Viewing ◽

Coherent Motion ◽

Slow Phase ◽

Infrared Reflection ◽

Sinusoidal Gratings ◽

Human Adults ◽

Normal Adults

AbstractWe evaluated the subcortical pathways’ contribution to human adults’ horizontal OKN by using a method similar to that used previously with cats (Harris & Smith, 1990; Smith & Harris, 1991). Five normal adults viewed plaids composed of two drifting sinusoidal gratings arranged such that their individual directions of drift were 60 deg or more from the direction of coherent motion of the overall pattern. Physiological evidence indicates that under monocular viewing, nasalward coherent motion gives advantage to any crossed subcortical contribution while temporalward coherent motion minimizes it. We recorded horizontal eye movement by infrared reflection and asked subjects to report the perceived direction of motion.During both binocular and monocular viewing, the direction of the slow phase of OKN fell closer to the direction of coherent movement than to that of the oriented components. Monocular viewing produced no nasal-temporal asymmetries in the influence of coherent motion on the direction of OKN. This suggests that in humans the influence of coherent motion is mediated primarily by cortical mechanisms and, unlike in cats, with little or no involvement of subcortical mechanisms in the generation of horizontal OKN.

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S-cone signals invisible to the motion system can improve motion extraction via grouping by color

Visual Neuroscience ◽

10.1017/s095252380909004x ◽

2009 ◽

Vol 26 (2) ◽

pp. 237-248 ◽

Cited By ~ 1

Author(s):

JASNA MARTINOVIC ◽

GEORG MEYER ◽

MATTHIAS M. MÜLLER ◽

SOPHIE M. WUERGER

Keyword(s):

Event Related Potentials ◽

Event Related Potential ◽

Coherent Motion ◽

Behavioral Experiment ◽

Motion Processing ◽

Global Motion ◽

Local Motion ◽

Motion System ◽

Motion Extraction ◽

Related Potentials

AbstractThe purpose of this study was to test whether color–motion correlations carried by a pure color difference (S-cone component only) can be used to improve global motion extraction. We also examined the neural markers of color–motion correlation processing in event-related potentials. Color and motion information was dissociated using a two-colored random dot kinematogram, wherein coherent motion and motion noise differed from each other only in their S-cone component, with spatial and temporal parameters set so that global motion processing relied solely on a constant L-M component. Hence, when color and the local motion direction are correlated, more efficient segregation of coherent motion can only be brought about by the S-cone difference, and crucially, this S-cone component does not provide any effective input to a global motion mechanism but only changes the color appearance of the moving dots. The color contrasts (vector length in the S vs. L-M plane) of both the dots carrying coherent motion and the dots moving randomly were fixed at motion discrimination threshold to ensure equal effectiveness for motion extraction. In the behavioral experiment, participants were asked to discriminate between coherent and random motion, and d′ was determined for three different conditions: uncorrelated, uncued correlated, and cued correlated. In the electroencephalographic experiment, participants discriminated direction of motion for uncued correlated and cued correlated conditions. Color–motion correlations were found to improve performance. Cueing a specific color also modulated the N1 component of the event-related potential, with sources in visual area middle temporal. We conclude that S-cone signals “invisible” to the motion system can influence the analysis by direction-selective motion mechanisms through grouping of local motion signals by color. This grouping mechanism must precede motion processing and is likely to be under attentional control.

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From spatial frequency contrast to edge preponderance: the differential modulation of early visual evoked potentials by natural scene stimuli

Visual Neuroscience ◽

10.1017/s095252381100006x ◽

2011 ◽

Vol 28 (3) ◽

pp. 221-237 ◽

Cited By ~ 23

Author(s):

BRUCE C. HANSEN ◽

THEODORE JACQUES ◽

AARON P. JOHNSON ◽

DAVE ELLEMBERG

Keyword(s):

Spatial Frequency ◽

Evoked Potentials ◽

Visual Evoked Potentials ◽

Luminance Contrast ◽

Systematic Investigation ◽

Natural Scenes ◽

Natural Scene ◽

Sinusoidal Gratings ◽

Edge Content ◽

Visual Evoked

AbstractThe contrast response function of early visual evoked potentials elicited by sinusoidal gratings is known to exhibit characteristic potentials closely associated with the processes of parvocellular and magnocellular pathways. Specifically, the N1 component has been linked with parvocellular processes, while the P1 component has been linked with magnocellular processes. However, little is known regarding the response properties of the N1 and P1 components during the processing and encoding of complex (i.e., broadband) stimuli such as natural scenes. Here, we examine how established physical characteristics of natural scene imagery modulate the N1 and P1 components in humans by providing a systematic investigation of component modulation as visual stimuli are gradually built up from simple sinusoidal gratings to highly complex natural scene imagery. The results suggest that the relative dominance in signal output of the N1 and P1 components is dependent on spatial frequency (SF) luminance contrast for simple stimuli up to natural scene imagery possessing few edges. However, such a dependency shifts to a dominant N1 signal for natural scenes possessing abundant edge content and operates independently of SF luminance contrast.

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From Elements to Perceptions

Perception ◽

10.1068/v970035 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 367-367

Author(s):

L Spillmann

Keyword(s):

Large Scale ◽

Receptive Fields ◽

Coherent Motion ◽

Future Research ◽

Natural Scenes ◽

Response Properties ◽

Area V2 ◽

Mach Bands ◽

Orientation Movement ◽

Motor Actions

Gestalt psychologists in the early part of the century challenged psychophysical notions that perceptual phenomena can be understood from a punctate (‘atomistic’) analysis of the elements present in the stimulus. Their ideas also inhibited later attempts to explain vision in terms of single-unit recordings from individual neurons. A rapprochement between Gestalt phenomenology and physiology seemed unlikely when the first ECVP was held in Marburg, Germany, in 1978. Since that time, response properties of neurons have been discovered that invite an interpretation of visual phenomena (including ‘illusions’) in terms of neuronal processing. Indeed, it is now possible to understand some Gestalt phenomena on the basis of known neurophysiological mechanisms. I begin by outlining the great strides that have been made since the advent of microelectrode recording from single neurons. Initially, cells (‘detectors’) selectively responding to the contrast, spatial frequency, wavelength, orientation, movement, and disparity of a stimulus placed in their receptive fields were used to interpret simple perceptual phenomena (eg, Mach bands, Hermann grids, tilt aftereffect, MAE). In recent years, cells at higher levels of the visual system have been discovered that might explain a number of more complex phenomena: the perception of illusory (occluded) contours by end-stopped cells in area V2, the filling-in of artificial scotomata by neurons in V3, colour constancy by ‘perceptive’ neurons in V4, and the perception of coherent motion in dynamic noise patterns by cells in MT. Studies of flow fields and biological motion in area MST have recently been added to account for our perceptions as we move through our environment. Prompted by these findings, a shift from local to global interactions ‘beyond the classical receptive field’ has taken place in our search for the neural substrates of perception. Current research has focused on three kinds of mechanisms: (i) converging feed-forward projections as the basis for new response properties emerging at higher levels, (ii) recruitment of lateral connections to explain filling-in, and (iii) backward propagation from higher to lower levels to account for binding and figure - ground segregation. How such mechanisms compute large-scale surface properties such as brightness, colour, and depth from local features—indeed how they construct the surfaces themselves from complex natural scenes—is only one of the many questions that are under scrutiny today. Future research will have to tackle the all-important question: How does the analysed information come together again? Furthermore, the contributions of eye movements, attention, learning, other sense modalities, and motor actions will have to be taken into consideration before we arrive at a more complete understanding of visual perception.

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Implied Motion From Form in the Human Visual Cortex

Journal of Neurophysiology ◽

10.1152/jn.00690.2005 ◽

2005 ◽

Vol 94 (6) ◽

pp. 4373-4386 ◽

Cited By ~ 58

Author(s):

Bart Krekelberg ◽

Argiro Vatakis ◽

Zoe Kourtzi

Keyword(s):

Visual Cortex ◽

Selective Adaptation ◽

Human Motion ◽

Coherent Motion ◽

Local Orientation ◽

Real Motion ◽

Motion Patterns ◽

Human Visual Cortex ◽

Implied Motion ◽

Glass Patterns

When cartoonists use speed lines—also called motion streaks—to suggest the speed of a stationary object, they use form to imply motion. The goal of this study was to investigate the mechanisms that mediate the percept of implied motion in the human visual cortex. In an adaptation functional imaging paradigm we presented Glass patterns that, just like speed lines, imply motion but do not on average contain coherent motion energy. We found selective adaptation to these patterns in the human motion complex, the lateral occipital complex (LOC), and earlier visual areas. Glass patterns contain both local orientation features and global structure. To disentangle these aspects we performed a control experiment using Glass patterns with minimal local orientation differences but large global structure differences. This experiment showed that selectivity for Glass patterns arises in part in areas beyond V1 and V2. Interestingly, the selective adaptation transferred from implied motion stimuli to similar real motion patterns in dorsal but not ventral areas. This suggests that the same subpopulations of cells in dorsal areas that are selective for implied motion are also selective for real motion. In other words, these cells are invariant with respect to the cue (implied or real) that generates the motion. We conclude that the human motion complex responds to Glass patterns as if they contain coherent motion. This, presumably, is the reason why these patterns appear to move coherently. The LOC, however, has different cells that respond to the structure of real motion patterns versus implied motion patterns. Such a differential response may allow ventral areas to further analyze the structure of global patterns.

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