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PubMed1975

The Aubert-Fleischl phenomenon: a temporal frequency effect on perceived velocity in afferent motion perception.

Apparent velocities of moving visual stimuli are known to be different depending on whether the subject pursues the stimulus (efferently controlled motion perception) or whether the eye is stationary and the image moves across the retina (afferent motion perception). Afferent motion perception of a periodic pattern or a moving single object causes overestimation of velocity (magnitude estimations) as compared to smooth pursuit. This socalled Aubert-Fleischl phenomenon is shown to depend on local temporal frequency stimulation on the retina caused by the repetitive passage of contrast borders of the moving periodic pattern. This is evidenced by the fact that for a given stimulus speed the amount of overestimation is a function of the spatial frequency of the pattern (or the angular subtend of a single moving object) and that the Aubert-Fleischl phenomenon is not observed if a single edge moves. Background characteristics seem not to influence the apparent velocity during smooth pursuit.

Adult↗
PubMed1985

Motion perception during dichoptic viewing of moving random-dot stereograms.

The relation between binocular and monocular motion perception was investigated. A random-dot stereogram (30 X 30 deg arc), containing a central figure seen in front of the background in stereoscopic vision, was viewed dichoptically by human subjects without a fixed visual frame of reference. The images seen by the right and left eye were moved laterally according to a triangular wave form, in counterphase, but with variable amplitude ratios. Under this condition only purely lateral movement and no motion in depth of the stereogram as a whole was perceived, while stereoscopic vision of the figure-background relation was maintained. The magnitude of the binocularly perceived lateral motion, signalled by manual tracking of the perceived displacement, equalled the algebraic mean of the monocular motion percepts. As a special case, when the two images forming the stereogram were moved with equal velocities but in opposite directions they were perceived as a completely stationary, fused image in stereoscopic depth. Only the addition of a stationary reference (a bar or grating seen by both eyes) resulted in the perception of motion in depth. We conclude that a visual frame of reference is essential for perception of motion in depth but not for perception of lateral movements. Moreover, it seems likely that not absolute binocular disparity (retinal locus differences) but relative binocular disparity (differences in angular distance between two or more corresponding features in the two retinal images) is a cue for perception of depth.

Convergence, Ocular↗
PubMed1994

Gibson's inspired but latent prelude to visual motion perception.

Gibson's 1954 article is paradoxical: This forward-looking review of visual motion perception anticipates developments in the field, yet those developments were achieved without closely following Gibson's footsteps. This commentary offers several possible reasons for the dormancy of Gibson's ideas about motion perception and evaluates contemporary work on motion perception in the context of Gibson's perspective.

History, 20th Century↗
PubMed1995

Global motion perception: no interaction between the first- and second-order motion pathways.

The experiments reported here address the issue of whether the pathways which extract motion from first-order and second-order spatial patterns remain separate or whether they combine at some higher level in the motion system to form a single pathway. The question is addressed by investigating the interaction of first-order and second-order stimuli in the processing of a global-motion stimulus [a variant of the task introduced by Newsome & Pare (Journal of Neuroscience, 8, 2201-2211, (1988)]. Two experimental procedures were used. The first consisted of determining the effect of the addition of dots of one type (e.g. first order) undergoing purely random motion on the ability to extract the global-motion signal carried by dots of the other type (e.g. second order). The second experimental procedure consisted of determining the effect of maintaining a coherent-motion signal in one type of dot, moving in the opposite direction to the global-motion direction, on the ability to extract the global-motion signal carried by dots of the other type. The dots were matched for their effectiveness in producing a global motion percept and the results for both procedures were the same. First-order dots impaired the ability to extract second-order global-motion, and second-order dots had no effect on first-order global-motion extraction. It is argued that the sensitivity of the second-order global-motion system to the first-order dots is due to the ability of the second-order local-motion detectors to detect these dots. The present results are thus interpreted as indicating that the first-order and second-order motion pathways remain separate up to and including the level in the motion system at which global-motion signals are extracted.

Humans↗
PubMed1997

The relationship between smooth pursuit performance, motion perception and sustained visual attention in patients with schizophrenia and normal controls.

BACKGROUND: In this study, we tested the hypothesis that low smooth pursuit gain in schizophrenia is related to an abnormality in motion perception. METHODS: The subjects were 19 schizophrenics treated with clozapine and 19 controls. In addition to smooth pursuit and motion perception paradigms, sustained attention was also assessed using a continuous performance task (CPT). RESULTS: In the patient group, there was a statistically significant negative correlation between smooth pursuit gain and motion perception threshold (r = -0.60, P < 0.01). This relationship was not secondary to attention deficits as assessed by the CPT. CONCLUSIONS: Our results are consistent with the notion that the smooth pursuit gain deficit is related to a deficit in motion perception rather than in attention. Brain area V5 (also referred to as "MT' in macaque), located in the parieto-occipital region, is known to be critically important both for motion perception and gain. Thus, our results point to an abnormality in this area in schizophrenia.

Adult↗
PubMed1996

Human self-motion perception during translatory vestibular and proprioceptive stimulation.

Self-motion perception in space was studied in normal human subjects during passive vestibular stimulation (lateral translation of whole body in space), proprioceptive stimulation (of feet relative to trunk) and combinations thereof with the eyes closed. Stimulation was sinusoidal, +/- 10 cm, over a frequency range of 0.025-0.4 Hz. Vestibular self-motion perception became increasingly underestimated at low frequency, due to a rather high detection threshold. Proprioceptive stimulation at low frequency elicited a small self-motion illusion. During body translation relative to the stationary feet (vestibular-proprioceptive combination) the magnitude of perceived self-motion was constant across frequency and its threshold was low, as if determined by proprioception alone. Nevertheless, the results can be interpreted in terms of a vestibular-proprioceptive interaction, in analogy to previous findings for rotational stimuli.

Evoked Potentials, Somatosensory↗
PubMed1994

Interaction between primary and secondary mechanisms in human motion perception.

Two layers of information processing can be distinguished as being involved in human motion perception. The primary motion detection stage processes displacements of the luminance distribution across space, such as experienced in natural scenes during the pursuit of moving targets. Primary motion detection is often investigated with artificial motion stimuli realized as random-dot kinematograms (RDKs). Such stimuli belong to the class of "Fourier motion", and their perception can be easily explained by means of elementary motion detectors (EMDs) of the correlation type. Other tasks require the comparison of motion signals from neighbouring areas in the visual field. The perception of the displacement of the motion distribution, for instance, has been accounted for by a secondary motion processing stage. In order to understand the principles of interaction between the motion in neighbouring areas of the visual field, we investigated the sensitivity of the human visual system for moving objects which are defined by moving dots in variable directions. These experiments lead to "secondary tuning curves" of direction discrimination for secondary motion as function of primary motion direction. A base level of sensitivity for all dot motion directions without a velocity component in the same direction of the object movement is enhanced when the object and the dots have a common velocity component. Thus primary motion in any direction can be exploited by the secondary stage, and primary and secondary system both feed into the object motion percept. Furthermore it is suggested from the shape of the secondary tuning curve that the outputs from the two layers of motion processing do not superimpose linearly, but are combined by some sort of veto-like mechanism which increases the directional sensitivity when the two processing layers experience movement along the same direction.

Adult↗
PubMed1998

Deficits and recovery of first- and second-order motion perception in patients with unilateral cortical lesions.

Unilateral lesions in the posterior parietal cortex can degrade motion perception in the contralesional visual hemifield. Our aim was to investigate whether deficits caused by cortical lesions may be different for first- and second-order motion perception, and to study the time scale of any potential recovery. In nine patients with circumscribed lesions mainly in the parietal and fronto-parietal cortex, thresholds for direction discrimination were measured for stimuli presented peripherally in their ipsi- and contralesional hemifield. Subjects had to identify the direction of a vertically moving object embedded in a background of dynamic random dot noise. The object consisted of various proportions of signal and noise dots. Signal dots were either (a) coherently moving in the same direction as the object (first-order), (b) stationary (second-order: drift-balanced), or (c) coherently moving in the opposite direction (second-order: theta). Noise dots were flickering. Two patients showed significant threshold elevations for all three types of motion stimuli presented in their contralesional hemifield, while thresholds for ipsilesional targets were unaffected. Neither showed any selective deficit of first- versus second-order motion perception, but second-order motion was more impaired. Their lesions probably included the motion area V5-MT, which was spared in the other seven patients. One of the patients, who was retested several times during a 27-month postlesional period, showed complete recovery for first- and second-order motion direction discrimination, as well as for the detection of speed differences.

Adult↗
PubMed1989

Some additional predictions and further tests of the Marr-Ullman model of motion perception.

The Marr-Ullman model for motion detection in the human visual system functions by means of the dual input of polarity-specific edge detectors and luminance change detectors. Moulden and Begg (1986) found a polarity-specific motion aftereffect which they claimed provided support for this dual input model. The logic of their experiment is examined, and it is shown that several additional predictions arise from the Marr-Ullman model, which were not supported by Moulden and Begg's study. A more powerful experiment was carried out and these additional predictions were disconfirmed, although the polarity-specific effect did emerge. A consideration of alternative explanations of this effect led to a second experiment in which an attempt was made to discover the actual determinants of the effect. This revealed that polarity-specific units are unlikely to play any part in the phenomenon. It was concluded, in the light of this and other evidence, that one of a class of alternative models is more likely to be the actual mechanism for motion perception. However, careful consideration of the Marr-Ullman model indicated that it may be untestable in principle if various differentially weighted levels of neural integration are envisaged.

Attention↗
PubMed1995

Motion perception deficits from midline cerebellar lesions in human.

Although visual motion processing is commonly thought to be mediated solely by visual cortical areas, this human lesion study suggests that the cerebellum also has a role. We found motion direction discrimination deficits in a group of patients with acute midline cerebellar lesions. Unlike normals and patients with hemispheric cerebellar lesions, these patients with midline lesions were unable to discern a global motion vector in a local stochastic motion display. This resembles the perceptual defect reported following cortical area MT lesions in primates. This motion perception deficit may result from damage to a cerebellar mechanism involved in perceptual stabilization. Disruption of this comparator mechanism is sufficient to produce a severe motion perception deficit even though cortical visual processing mechanisms are still intact.

Adult↗
PubMed1990

[An experiment on the theory of visual motion perception].

Two classes of theories of motion perception were studied: correlation and gradient models (in the sense of D. Marr). Random-dot kinematograms with a shifted square were presented to subjects, and the 80% threshold for detection of correct direction of movement was determined. Correlation models predict scale invariance, that is, a constant shift measured in units of texture elements of the translated pattern in spite of a geometric magnification. This was refuted for all subjects. The increase of the recognizable translation with the area of the translated form was verified except for the patterns with the largest texture elements (8 minutes of arc). This prediction, however, is not very specific for competing theories. Gradient models are not yet fully specified, and they contain some free parameters. They cannot be tested strictly, but there exist reasonable numerical parameter values by which our data can be satisfactorily explained.

Adult↗
PubMed1986

Object-motion detection affected by concurrent self-motion perception: psychophysics of a new phenomenon.

Thresholds for object-motion detection are significantly raised when concurrent self-motion perception is induced by either vestibular, or visual, or cervico-somatosensory stimulation. Active sinusoidal horizontal head oscillations with compensatory vestibulo-ocular reflex (VOR) and foveal or eccentrical target presentation; 'passive' head movements with fixation suppression of the VOR; pure body oscillations with the head fixed in space (cervical stimulation); optokinetically induced apparent self-motion (circularvection). This new visual phenomenon of a physiological 'inhibitory interaction' between object- and self-motion perception seems to have a somatosensory motor analogue. It may reflect the disadventageous side effect due to unspecificness of an otherwise beneficial space constancy mechanism, which provides us with the image of a stable world during locomotion.

Adolescent↗
PubMed1989

Monocular motion sensing, binocular motion perception.

The two-process account of motion perception and its binocular organization were addressed in experiments on apparent movement (AM) with three types of grating: sinusoidal; random bar width; and square-wave with missing fundamental (MF). Monocular MF gratings sampled four times per cycle of drift always appeared to move backwards. Here AM was unrelated to the spatial appearance of the pattern, and followed the motion of the dominant spatial frequency component (the third harmonic). We take this reversed AM to be characteristic of "short-range" motion sensors. It did not occur dichoptically, implying that the direction-selective mechanism of motion sensors is purely monocular. AM was seen with dichoptic presentation for all three types of grating. Performance improved with the length of the stimulus sequence, as predicted by probability summation. This result reconciles previous positive and negative findings on dichoptic AM. The perceived direction of dichoptic AM was consistent with polarity-selective matching of features over time (the "long-range process"). The most telling effect supporting feature-matching in dichoptic motion was that dichoptic MF motion reversed direction with a change in the visible features of the pattern (induced by changes in contrast and pulse duration); monocular apparent motion did not. Two routes from spatial frequency channels to the perception of object motion are discussed.

Contrast Sensitivity↗
PubMed1992

Absence of smooth motion perception in color vision.

We have tested the behavioral evidence for a separation of the processing of color contrast from motion in the human visual system. Two different aspects of motion perception are examined; the identification of the direction of movement of a chromatic grating and the perception of smooth motion. The results show that color vision is at no great disadvantage in the identification of direction of movement, since this can be done at color contrasts quite close to detection threshold over a wide range of spatial and temporal frequencies. However, we find that subjects can identify direction without having the genuine perception of smooth motion. Smooth motion perception is revealed to be highly impaired since it is detected only at very high color contrasts and over a narrow range of spatial temporal conditions.

Color Perception↗
PubMed1997

Second-order motion perception in peripheral vision: limits of early filtering.

Spatial and temporal analysis of contrast-modulated sine-wave gratings reveals that the second-order motion stimulus contains two sidebands, with equal energy but moving in opposite directions, flanking a stationary carrier. Any early linear spatial filtering process in the visual system that attenuates one sideband more than the other will be detrimental to the balance between the two sidebands, so that the perceived direction of the carrier might be opposite to that of the envelope motion. We tested this hypothesis by using contrast-modulated gratings presented centrally or at 20 deg in the horizontal nasal field with a two-alternative forced-choice staircase paradigm. We found that when the envelope frequency was close to that of the carrier, a second-order stimulus whose envelope motion direction was correctly identified in the fovea appeared to drift in the opposite direction in the periphery. Further increasing the envelope spatial frequency resulted in a reversed motion percept in both central and peripheral viewing conditions. For subjects to identify correctly the direction of motion of the envelope, the spatial frequency ratio of the carrier to the envelope had to be more than 2 in the fovea and more than 6 in the periphery. These phenomena in second-order motion perception can be explained by a linear model of motion detection with an early spatial filtering process. Further experiments and computer simulation show that undersampling of the carrier has little effect on second-order motion perception in the periphery, as long as the carrier is detectable.

Adult↗
PubMed1995

The consequences of inactivating areas V1 and V5 on visual motion perception.

We studied the capacity of normal humans to discriminate the direction of motion of visual stimuli when areas V1 or V5 were reversibly inactivated with transcranial magnetic stimulation. We found that (i) magnetic stimulation of V5 at intervals of -20 to +10 ms before or after the onset of visual stimulation was effective in abolishing motion perception--other delays were not; (ii) magnetic stimulation of V1 abolished motion perception only marginally and at delays which were significantly different from those obtained with V5, the stimulation now being effective only at delays of 60-70 ms after the onset of visual stimulation. We conclude (i) that stimulation of V5 is a much more potent way of inducing akinetopsia (motion imperception) than stimulation of V1; (ii) that perceptually effective visual motion signals reach V5 at or before 30 ms and reach V1 at or before 60 ms--consequently, perceptually effective motion signals reach V5 before they reach V1; (iii) that, given the time course of arrival of signals in V1 and V5, it takes about 30-50 ms for signals from V1 to reach V5. We conclude further that there are probably two components reaching V5 from the retina, a fast one which bypasses V1 and a slow one which reaches it through V1.

Brain Mapping↗
PubMed1998

Anisotropies in visual motion perception: a fresh look.

We measured motion-detection and motion-discrimination performance for different directions of motion, using stochastic motion sequences. Random-dot cinematograms containing 200 dots in a circular aperture were used as stimuli in a two-interval forced-choice procedure. In the motion-detection experiment, observers judged which of two intervals contained weak coherent motion, the other internal containing random motion only. In the direction-discrimination experiment, observers viewed a standard direction of motion followed by comparison motion in a slightly different direction. Observers indicated whether the comparison was clockwise or counterclockwise, relative to the standard. Twelve directions of motion were tested in the detection task and five standard directions (three cardinal directions and two oblique directions) in the discrimination task. Detection thresholds were invariant with direction of motion, but direction-discrimination thresholds were significantly higher for motion in oblique directions, even at low-coherence levels. Results from control conditions ruled out monitor artifacts and indicate that the oblique effect is relative to retinal coordinates. These results have broad implications for computational and physiological models of motion perception.

Anisotropy↗
PubMed1997

Visually induced motion perception and visual control of postural sway in congenital nystagmus.

In congenital nystagmus (CN) the threshold for detecting motion of visual objects is increased. To determine whether this increase is due to a deterioration of visual motion signals or whether visual-vestibular interactions (which are necessary to judge object-motion in space) are also involved we examined how CN patients use visual motion signals to evaluate self-motion in perceptual and behavioral tasks. Using an optokinetic drum we measured the minimum optokinetic acceleration necessary to induced motion perception of the visual environment in CN patients. This threshold was significantly elevated in the CN patients compared with normals (20.1 deg/s2 to 3.25 deg/s2). We further addressed the question whether the elevation of this threshold is due to a deficiency in evaluating visual motion in general or to a specific modification affecting the percept of visual object-motion with respect to the inertial reference only. We thus measured the latency of visually induced self-motion perception, which was found to be very similar or even slightly smaller (1.7 +/- 0.7 s) compared with normals (2.2 +/- 1.7 s). Moreover, subjects with CN were found to use vision quite efficiently for the visual stabilization of posture (Romberg quotient 2.0 +/- 1.16), even if they did not reach the level of normals (Romberg quotient 3.7 +/- 1.1). The results indicate that CN affects the estimate of object-motion in a specific and much more severe way than the estimate of self-motion. The minimal effect of CN on self-motion perception can be explained by the low pass characteristics of the optokinetic input to self-motion perception. The specific deficiency in detecting object-motion indicates that adaptation to CN occurs on the level of visual--vestibular interactions for the perception of visual object-motion and not on the level of visual motion signals.

Adolescent↗