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At least 217 records · Page 12Linked to original sources
PubMed2003

The motion reverse correlation (MRC) method: a linear systems approach in the motion domain.

We introduce the motion reverse correlation method (MRC), a novel stimulus paradigm based on a random sequence of motion impulses. The method is tailored to investigate the spatio-temporal dynamics of motion selectivity in cells responding to moving random dot patterns. Effectiveness of the MRC method is illustrated with results obtained from recordings in both anesthetized cats and an awake, fixating macaque monkey. Motion tuning functions are computed by reverse correlating the response of single cells with a rapid sequence of displacements of a random pixel array (RPA). Significant correlations between the cell's responses and various aspects of stimulus motion are obtained at high temporal resolution. These correlations provide a detailed description of the temporal dynamics of, for example, direction tuning and velocity tuning. In addition, with a spatial array of independently moving RPAs, the MRC method can be used to measure spatial as well as temporal receptive field properties. We demonstrate that MRC serves as a powerful and time-efficient tool for quantifying receptive field properties of motion selective cells that yields temporal information that cannot be derived from existing methods.

Animals↗
PubMed1997

Human brain potentials observed using the line-motion method: the neurophysiological correlates of visual illusory motion perception.

This study shows the temporal dynamics of neurophysiological activities in illusory motion perception. Event-related brain potentials were recorded from 12 healthy subjects while they performed a two-alternative (motion/no motion), forced-choice task using the line motion method. Amplitudes of a late positive component at Fz, Cz, Pz, O1 and O2 increased as cue lead time (CLT) increased. At a CLT of 50 ms, the amplitudes of the late positive component (the peak latency at O1, O2: 310 ms; Fz, Cz, Pz: 360-390 ms) observed during illusory motion perception was larger than that observed during no motion perception, even though the physical stimuli were the same. These results suggest that the perception of illusory motion correlates to a relatively late stage of visual information processing.

Adult↗
PubMed1998

Motion evoked brain potentials parallel the consistency of coherent motion perception in humans.

The perception of global coherent motion perception in complex motion patterns containing different direction vectors was investigated. Random dot kinematograms (RDK), plaids and fragmented plaid pattern were presented in which direction vectors of the moving elements were varied. In order to elicit coherent motion perception, all elements were displaced in the same direction (delta0 degrees). In a second condition, fifty percent of the elements were moved diagonally downwards to the left, with the remaining elements moving orthogonally (delta 90 degrees). Simultaneously with psychophysical judgements on the perceived motion direction, visual evoked potentials (VEPs) were recorded at occipital electrode positions. Onset of a global coherent motion was associated with a VEP negativity occurring at about 200 ms. The amplitude of this component was clearly reduced when local ambiguous signals could not be integrated to produce the perception of global coherent motion.

Adult↗
PubMed2001

Visual search for motion-form conjunctions: is form discriminated within the motion system?

Motion-form conjunction search can be more efficient when the target is moving (a moving 45 degrees tilted line among moving vertical and stationary 45 degrees tilted lines) rather than stationary. This asymmetry may be due to aspects of form being discriminated within a motion system representing only moving items, whereas discrimination of stationary items relies on a static form system (J. Driver & P. McLeod, 1992). Alternatively, it may be due to search exploiting differential motion velocity and direction signals generated by the moving-target and distractor lines. To decide between these alternatives, 4 experiments systematically varied the motion-signal information conveyed by the moving target and distractors while keeping their form difference salient. Moving-target search was found to be facilitated only when differential motion-signal information was available. Thus, there is no need to assume that form is discriminated within the motion system.

Adolescent↗
PubMed1999

Motion streaks provide a spatial code for motion direction.

Although many neurons in the primary visual cortex (V1) of primates are direction selective, they provide ambiguous information about the direction of motion of a stimulus. There is evidence that one of the ways in which the visual system resolves this ambiguity is by computing, from the responses of V1 neurons, velocity components in two or more spatial orientations and then combining these velocity components. Here I consider another potential neural mechanism for determining motion direction. When a localized image feature moves fast enough, it should become smeared in space owing to temporal integration in the visual system, creating a spatial signal-a 'motion streak'-oriented in the direction of the motion. The orientation masking and adaptation experiments reported here show that these spatial signals for motion direction exist in the human visual system for feature speeds above about 1 feature width per 100 ms. Computer simulations show that this psychophysical finding is consistent with the known response properties of V1 neurons, and that these spatial signals, when appropriately processed, are sufficient to determine motion direction in natural images.

Computer Simulation↗
PubMed1994

The duration of the motion aftereffect following adaptation to first-order and second-order motion.

The magnitude of the motion aftereffect (MAE) obtained following adaptation to first-order or to second-order motion was measured by estimating its duration. The second-order adaptation stimulus was composed of contrast-modulated noise produced by multiplying two-dimensional (2-D) noise by a drifting 1 cycle deg-1 sine grating. The first-order adaptation stimulus was composed of luminance-modulated noise produced by summing, rather than multiplying, the noise and the sine grating. The test stimuli were directionally ambiguous motion patterns composed of either two oppositely drifting sine gratings added to noise or the contrast-modulated equivalent. The adaptation and test stimuli were equated for visibility by presenting them at the same multiple of direction-identification threshold. All possible combinations of first-order and second-order adaptation and test stimuli were examined in order to compare the magnitudes of the MAEs obtained following same adaptation and cross adaptation. After adaptation the test stimuli always appeared to drift coherently in the direction opposite to that of adaptation and the magnitudes of this MAE were very similar for all conditions examined. Statistical analyses of the results showed that there was no significant difference between the durations of the MAEs obtained in the same-adaptation and cross-adaptation conditions. The cross-adaptation effects suggest that either first-order or second-order motion are detected by a common low-level mechanism, or that separate parallel motion-detecting mechanisms exist, for the two types of motion, that interact at some later stage of processing.

Humans↗
PubMed1997

Can illusory motion disrupt tracking real motion?

When rotating stripes or other periodic stimuli cross the retina at a critical rate, a reversal in the direction of motion of the stimuli is often seen. This illusion of motion perception was used to explore the roles of retinal and perceived motion in the generation of optokinetic nystagmus. Here we show that optokinetic nystagmus is disrupted during the perception of this illusion. Thus, when perceived and actual motion are in conflict, subjects fail to track the veridical movement. This observation suggests that the perception of motion can directly influence optokinetic nystagmus, even in the presence of a moving retinal image. A conflict in the neural representation of motion in different brain areas may explain these findings.

Humans↗
PubMed1999

The influence of structure from motion on motion correspondence.

The visual system has a remarkable ability to reconstruct 3-D structure from moving 2-D features. The processing of structure from motion is generally thought to consist of two stages. First, the direction and speed of features is measured (2-D velocity measurement) and, second, 3-D structure is reconstructed from the measured 2-D velocities (3-D structure recovery). Most models have assumed that these stages occur in a bottom-up fashion. Here, however, we present evidence that the 3-D structure-recovery stage influences the 2-D velocity-measurement stage. We developed a stimulus in which two perceptual modes of motion correspondence (one-way translation versus oscillation), and two perceptual modes of 3-D surface structure (flat surface versus cylinder) could be achieved. We found that the likelihood of perceiving both one-way motion and cylindrical structure increased in similar ways with increasing frame duration. In subsequent experiments we found, first, that a higher likelihood of perceiving one-way motion did not affect the likelihood of perceiving cylindrical structure; and, second, that a higher likelihood of perceiving cylindrical structure increased the likelihood of perceiving one-way motion. These results suggest that the higher, 3-D structure-recovery stage may influence the lower, 2-D motion-correspondence stage. This result is not in accordance with most computational models that assume that there is only one-way, feedforward information processing from the 2-D velocity (energy)-measurement stage to the 3-D structure-recovery stage. Perhaps, one of the roles of feedback processing is to seek consensus of the information processed in different stages.

Female↗
PubMed2003

Motion induction from biological motion.

A new type of motion illusion is described in which ambiguous motion becomes unidirectional on superimposition of a human figure walking on a treadmill. A point-light walker in profile was superimposed on a vertical counterphase grating backdrop. Eleven naïve observers judged the apparent direction of motion against the grating as left or right in a two-alternative forced-choice task and found that the grating appeared to drift in a direction opposite to the walking. The illusion disappeared when the point lights moved in scrambled configurations. This indicates that the illusion is caused by biological motion that provides recognition of gaits. A human figure walking backwards produced no illusion because of the difficulty in identifying the gait. This indicates that the illusion is determined by translational motion rather than form represented from biological motion.

Adult↗
PubMed1999

Perceptual learning in motion discrimination that generalizes across motion directions.

When human subjects discriminate motion directions of two visual stimuli, their discrimination improves with practice. This improved performance has been found to be specific to the practiced directions and does not transfer to new motion directions. Indeed, such stimulus-specific learning has become a trademark finding in almost all perceptual learning studies and has been used to infer the loci of learning in the brain. For example, learning in motion discrimination has been inferred to occur in the visual area MT (medial temporal cortex) of primates, where neurons are selectively tuned to motion directions. However, such motion discrimination task is extremely difficult, as is typical of most perceptual learning tasks. When the difficulty is moderately reduced, learning transfers to new motion directions. This result challenges the idea of using simple visual stimuli to infer the locus of learning in low-level visual processes and suggests that higher-level processing is essential even in "simple" perceptual learning tasks.

Humans↗
PubMed1991

Why is the driver rarely motion sick? The role of controllability in motion sickness.

The central hypothesis of the work is that the dimension of control-no control plays an important role in motion sickness. Although it is generally agreed that having control over a moving vehicle greatly reduces the likelihood of motion sickness, few studies have addressed this issue directly, and the theoretical explanation for this phenomenon is not completely clear. In this study, we equated groups differing in controllability for head movement, vision, activity, and predictability, which have often been suggested in the literature as explanations for the driver's immunity to motion sickness. Twenty-two pairs of yoked subjects were exposed to nauseogenic rotation. One subject of each pair had control over the rotation and head movements, while the other was exposed passively to the same motion stimulus. Subjects who had control reported significantly fewer motion sickness symptoms and less of a decrement in their well-being, as compared to the yoked subject without control. The results are discussed in relation to Reason's sensory rearrangement theory and the concept of feed-forward mechanisms in motion perception.

Adult↗
PubMed2003

Visual motion influences the contingent auditory motion aftereffect.

In this study, we show that the contingent auditory motion aftereffect is strongly influenced by visual motion information. During an induction phase, participants listened to rightward-moving sounds with falling pitch alternated with leftward-moving sounds with rising pitch (or vice versa). Auditory aftereffects (i.e., a shift in the psychometric function for unimodal auditory motion perception) were bigger when a visual stimulus moved in the same direction as the sound than when no visual stimulus was presented. When the visual stimulus moved in the opposite direction, aftereffects were reversed and thus became contingent upon visual motion. When visual motion was combined with a stationary sound, no aftereffect was observed. These findings indicate that there are strong perceptual links between the visual and auditory motion-processing systems.

Attention↗
PubMed1995

Direct perception of three-dimensional motion from patterns of visual motion.

Measurements of retinal motion along a set of predetermined orientations on the retina of a moving system give rise to global patterns. Because the form and location of these patterns depend purely on three-dimensional (3D) motion, the effects of 3D motion and scene structure on image motion can be globally separated. The patterns are founded on easily derivable image measurements that depend only on the sign of image motion and do not require information about optical flow. The computational theory presented here explains how the self-motion of a system can be estimated by locating these patterns.

Mathematics↗
PubMed1986

Motion selectivity in macaque visual cortex. III. Psychophysics and physiology of apparent motion.

We have conducted physiological and psychophysical experiments to identify possible neural substrates of the perception of apparent motion. We used identical sequences of flashed stimuli in both sets of experiments to better compare the responses of cortical neurons and psychophysical observers. Physiological data were obtained from two cortical visual areas, striate cortex (V1) and the middle temporal area (MT). In the previous paper we presented evidence that neuronal thresholds for direction selectivity in extrastriate area MT were similar to psychophysical thresholds for motion perception at the largest effective interflash interval, and thus speed, for a given eccentricity. We now examine physiological and psychophysical thresholds for a broad range of speeds to determine whether such a correspondence exists for speeds below the upper threshold considered in the previous paper. Stimuli were presented in stroboscopic motion of constant apparent speed while the spatial and temporal interflash intervals were systematically varied. For each neuron we measured the largest spatial interval that elicited directionally selective responses at each of several apparent speeds. We calculated the composite performance of neurons in both MT and V1 by averaging the spatial interval necessary for direction selectivity at each apparent speed. We employed the same apparent-motion stimuli for psychophysical experiments with human subjects in which we measured the spatial interval necessary for the perception of motion over a similar range of apparent speeds. We obtained a composite profile of psychophysical performance by averaging thresholds across subjects at each apparent speed. For high apparent speeds, physiological data from MT, but not V1, corresponded closely to the psychophysical data as suggested in the preceding paper. For low apparent speeds, however, physiological data from MT and V1 were similar to each other and to the psychophysical data. It would appear, therefore, that neurons in either V1 or MT could mediate the perceptual effect at low speeds, whereas MT is a stronger candidate for this role at high speeds. We suggest that the neuronal substrate for apparent motion may be distributed over multiple cortical areas, depending upon the speed and spatial interval of the stimulus.

Animals↗
PubMed1993

Motion at isoluminance: motion dead zones in three-dimensional color space.

Under some conditions, moving isoluminant stimuli perceptually slow down or even appear to stop. The purpose of the experiment was to explore the shape of the motion dead zone, the region of color space over which the perception of stopped motion occurs. Subjects viewed a small patch of moving grating (2.3 deg x 2.3 deg, 1.3 cycles/degree, 2.9 deg/s), that was spatially modulated in chromaticity, luminance, or both, presented either foveally or at 2-deg eccentricity. The bars of the grating moved from both edges inward toward the center of the patch. Subjects set perceptual motion boundaries by adjusting the contrast of the luminance-modulation component of the grating. Over most or all of the available gamut of chromatic contrasts, the upper and lower boundaries of the motion dead zone formed two parallel planes near the V lambda-isoluminant plane in three-dimensional color space. The data thus suggest that under the conditions of the experiment, perceptual-motion boundaries are determined largely or entirely by the luminance contrast of the stimulus. The data also provide the most extensive evidence available to date for the additivity of motion photometry.

Adult↗
PubMed2004

"Conflicting" motion cues to the visual and vestibular self-motion systems around 0.06 Hz evoke simulator sickness.

The basic question this research addressed was, how does simulator sickness vary with simulated motion frequency? Participants were 11 women and 19 men, 20 to 63 years of age. A visual self-motion frequency response curve was determined using a Chattecx posture platform with a VR4 head-mounted display (HMD) or a back-projected dome. That curve and one for vestibular self-motion specify a frequency range in which vestibular and visual motion stimuli could produce conflicting self-motion cues. Using a rotating chair and the HMD, a third experiment supported (p < .01) the hypothesis that conflicting cues at the frequency of maximum "crossover" between the curves (about 0.06 Hz) would be more likely to evoke simulator sickness than would conflicting cues at a higher frequency. Actual or potential applications of this work include a preliminary design guidance curve that indicates the frequency range of simulated motion that is likely to evoke simulator or virtual reality sickness; for simulators intended to operate in this frequency range, appropriate simulator sickness interventions should be considered during the design process.

Computer Simulation↗
PubMed1996

Perceiving self-motion in depth: the role of stereoscopic motion and changing-size cues.

During self-motions, different patterns of optic flow are presented to the left and right eyes. Previous research has, however, focused mainly on the self-motion information contained in a single pattern of optic flow. The present experiments investigated the role that binocular disparity plays in the visual perception of self-motion, showing that the addition of stereoscopic cues to optic flow significantly improves forward linear vection in central vision. Improvements were also achieved by adding changing-size cues to sparse (but not dense) flow patterns. These findings showed that assumptions in the heading literature that stereoscopic cues facilitate self-motion only when the optic flow has ambiguous depth ordering do not apply to vection. Rather, it was concluded that both stereoscopic and changing-size cues provide additional motion-in-depth information that is used in perceiving self-motion.

Adolescent↗
PubMed1993

Infant use of relative motion as information for form: evidence for spatiotemporal integration of complex motion displays.

Previous studies of infants' ability to integrate and to utilize relative motion as information for form in the absence of structural cues have primarily involved motions that are uniform in rate, direction, and path within the form to be constructed. In the present study, we examined infants' ability to integrate relative motion information from motions that are nonuniform along these dimensions, and from this integrative process to construct a coherently rotating two-dimensional form. Infants' ability to integrate nonuniform motion was measured with regard to their ability to discriminate the rotating form from a noncoherent control display containing the same absolute motions. The results showed that discrimination of the coherent and incoherent displays was not demonstrated until 7 months of age. Two additional experiments were conducted to rule out the possibility that this discrimination was based on the detection of local regions of coherence, rather than the perception of the global rotating form. In both experiments, the results did not support discrimination based exclusively on local cues alone. From the combined results of all three experiments, we conclude that infants demonstrate the capacity to integrate the information contained within nonuniform trajectories into a coherent structure by 7 months of age.

Age Factors↗