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PubMed1996

[Informative value of psychophysical examinations aside from conventional white-white perimetry].

In addition to routine light-sense perimetry testing, elementary visual function, i.e., light difference sensitivity, numerous methods and procedures were developed to test more complex psychophysical threshold criteria in glaucoma patients in order to detect functional glaucomatous loss earlier. The various methods differ with respect to the area of the visual field tested (central, perimetric, global or Ganzfeld stimulation) and the psychophysical threshold criteria (spatial and/or temporal transfer, color, complex criteria including form perception, etc.). Two domain proved to be of special interest: examination of the temporal transfer properties (flicker stimulation, motion perception, "motion-defined-form") and testing of the short-wave-length cone system (blue/yellow perimetry). The blue cone system is part of the parvocellular pathway, criteria in the field of temporal transfer may be allocated to the magnocellular pathway. There is histopathological evidence that ganglion cell axons of the magnocellular system are prone to glaucomatous damage in an earlier stage of the disease. There may even be some kind of specific damage. The role of various psychophysical procedures are discussed with reference to data in the literature and own experience with special emphasis on the practical applicability for early diagnosis of functional glaucomatous damage.

Color Perception Tests↗
PubMed2006

Perception of biological motion from limited-lifetime stimuli.

The visual perception of human movement from sparse point-light walkers is often believed to rely on local motion analysis. We investigated the role of local motion in the perception of human walking, viewed from the side, in different tasks. The motion signal was manipulated by varying point lifetime. We found the task of coherence discrimination, commonly used in biological motion studies, to be inappropriate for testing the role of motion. A task requiring temporal information showed a strong performance drop when fewer points were used or when the image sequence was sampled and displayed at a reduced frame rate. Irrespective of the frame rate, performance did not vary with point lifetime. We concluded that local motion is not required for the perception of tested biological movements, suggesting that the analysis of biological motion does not benefit from examining local motion. The reliance of perception on the number of displayed points and frames supports the idea that biological motion is perceived from a sequence of spatiotemporally sampled forms.

Child↗
PubMed1987

Errors in direction-of-motion discrimination with complex stimuli.

The direction of apparent motion in a complex pattern comprising a static 1-cycle/degree (c/deg) grating and a moving 3-c/deg grating changes with stimulus duration. At durations longer than about 150 msec, motion is seen almost veridically; the motion of the 3-c/deg grating, which is seen correctly, merely induces in the 1-c/deg grating a weak apparent motion in the opposite direction. At shorter durations, however, the only motion seen is in the opposite direction from that which, in fact, occurs. The reversed apparent motion is both compelling and consistent; it is reported both by naive and by experienced observers, and, although it only occurs for certain ranges of spatial frequency, contrast and duration, the ranges are substantial. The reversal appears to be almost independent of the temporal frequency and the spatial phase of the stimulus; it occurs both for discrete and for continuous motion. It seems likely that the apparent motion with short duration stimuli reveals properties of local visual movement detection previously unknown and difficult to account for within the framework of current models of motion perception.

Discrimination, Psychological↗
PubMed1990

Contrast dependence of short-range apparent motion.

The apparent motion of band-pass filtered random dot kinematograms was assessed by measurements of two alternative direction discrimination performance. In the case of two-dimensional (isotropically filtered) stimuli, the results were largely independent of contrast: at Michelson contrasts of 5 and 50%, near-perfect direction discrimination was obtainable for a limited range of displacements. However for one-dimensional (grating) stimuli, apparent motion seems to be highly dependent on contrast. At 5% contrast, performance was comparable to that obtained with the two-dimensional stimuli. At 50% contrast the motion percept broke down to a large extent, with consistently poor direction discrimination being obtained. The breakdown of apparent motion is interpreted in terms of a decreased signal-to-noise ratio in the pooled response of motion detectors that are tending to contrast saturation. Here, "noise" refers to the sampling components present in any apparent motion sequence. Evidence relating to the sampling frequency of the motion sequence is presented to support the hypothesis. It is argued that the discrepancy between the results obtained with one- and two-dimensional stimuli support the idea that motion is initially encoded by orientationally tuned mechanisms.

Contrast Sensitivity↗
PubMed1992

Lateral motion bias associated with reading direction.

We found that when Americans view ambiguous lateral long-range apparent motion, they exhibit a robust bias to experience leftward movement. In successive experiments, right-handers and left-handers, and left-side drivers from Japan equally manifested this leftward bias. However, bilingual viewers whose first language reads from right to left exhibited no lateral bias. Furthermore, the bilingual sample produced a significant correlation between exposure to English and extent of leftward motion bias. The findings provide strong evidence that reading habits can influence directionality in motion perception.

Automobile Driving↗
PubMed1997

Is facilitation responsible for the "motion induction" effect.

When a horizontal bar is presented after a single dot is shown at one of its ends, an illusory motion is seen which has been dubbed "motion induction" in the literature. The phenomenon has been attributed to a facilitation process which asymmetrically modulates the inputs to motion detectors, for instance by some sort of changes in processing speed. Computer simulations of motion detector arrays show, however, that this basic effects has to be expected from the properties of simple motion detectors. It has been recently reported that the strength of the illusory motion increases with the subjective salience of the inducing element. New computer simulations demonstrate that this observation can be related to the control of the local gain of motion detector input signals by the feature contrast in a particular region of the stimulus. High-level attentional mechanisms or changes in transmission speed are not required to explain these phenomena. The implications of such local gain-control mechanisms for our understanding of second-order motion perception are discussed.

Attention↗
PubMed2002

Apparent motion processing in strabismic observers with varying levels of stereo vision.

Deficits of motion processing have been reported in individuals with infantile strabismus. Here we examined motion perception in early and late onset strabismic individuals with varying levels of stereo acuity using the Fine Grain Motion Illusion (FGMI). The FGMI is an illusion of motion, where under some conditions, observers report exaggerated motion. It has been speculated that this illusion is due to the spatial range of cortical cells stimulated. We used this illusion to compare this motion exaggeration in the central vision of both the deviating and non-deviating eye of strabismic observers with control eyes. While individuals with early onset strabismus showed some mild exaggeration of motion, those with low stereo acuity, regardless of age at onset, showed significantly larger exaggeration of this motion illusion in both the deviating and non-deviating eyes as compared with control observers. These results might indicate that this illusion and stereopsis involve common mechanisms.

Adolescent↗
PubMed2002

The importance of head-free gaze control in humans performing a spatial orientation task.

The present study aimed at investigating how a specific instruction concerning gaze orientation, which involved active head motion, could influence the performance of human subjects in a self-controlled whole-body rotation task in the dark. Subjects were seated on a mobile robotic chair that they controlled using a joystick. They were asked to perform 360 degrees rotations while maintaining, when possible, the gaze on the estimated position of an earth-fixed target. Subjects performed better when gazing at this target than when no target was shown. Furthermore, performance was significantly related to head stabilization in space. The results reveal the importance of head-free gaze control for spatial orientation in so far as it may involve spatial reference cues and sensory signals of different modalities, which may be beneficial to self-motion perception.

Adult↗
PubMed1999

Correlational analysis of acoustic cues for the discrimination of auditory motion.

The sound of a source moving in a straight path and passing directly in front of the listener on the azimuthal plane was synthesized over headphones to include three dynamic cues for motion: Doppler effect, overall intensity, and interaural time difference. Discriminability of a change in displacement, velocity, and acceleration of this source was measured using a standard two-interval, forced-choice procedure. In each case, the relative reliance or weight given to the three acoustic cues was estimated from correlations of the listener's response with small independent pertubations imposed on cues from trial to trial. Group estimates of threshold agreed well with results from past studies, while the obtained pattern of weights depended on the individual, starting velocity, and discrimination task. For the discrimination of displacement at moderate velocity (10 m/s), responses were most highly correlated with intensity or interaural time difference. For the discrimination of velocity and, to a lesser extent, acceleration, responses were most highly correlated with Doppler effect. At higher velocity (50 m/s) responses in all discrimination tasks were most strongly correlated with Doppler effect with few exceptions. Randomizing source spectrum or roving distance of the source from trial to trial did not significantly affect the pattern of results. The results suggest that motion perception is mutable, and not in all cases based on a single invariant acoustic cue.

Auditory Perception↗
PubMed2004

Multiple reference frames for motion in the primate cerebellum.

Knowledge of body motion through space is necessary for spatial orientation, self-motion perception, and postural control. Yet, sensory afferent signals may not directly provide such information to the brain. Because motion detected by the vestibular end organs is encoded in a head-fixed frame of reference, a coordinate transformation is thus required to encode body motion. In this study, we investigated whether cerebellar motion-sensitive neurons encode the translation of the body through space. We systematically changed both the direction of motion relative to the body and the static orientation of the head relative to the trunk. The activities of motion-sensitive neurons in the most medial of the deep cerebellar nuclei, the rostral fastigial nucleus, were compared with those in the brainstem vestibular nuclei. We found a distributed representation of reference frames for motion in the rostral fastigial nucleus, in contrast to cells in the vestibular nuclei, which primarily encoded motion in a head-fixed reference frame. This differential representation of motion-related information implies potential differences in the functional roles of these areas.

Acceleration↗
PubMed1994

Injury and proprioception in the lower back.

No known research has attempted to quantify proprioception of the lower back or to examine the relationship between injury and proprioception in this region. The primary purpose of this study was to explore relationships between low back injury and proprioception of the lower back. Subjects were 88 working male firefighters from public emergency medical service departments. Three types of lower back proprioception (passive motion threshold, directional motion perception, and repositioning accuracy) were tested. Each type of proprioception was examined in the three primary planes of motion using a device designed by the author. Some anthropometric and personal variables were statistically controlled. All variables underwent multiple correlation analysis. The primary findings were: 1) longevity factors [age (r = .30, p < .01) and years of experience (r = .35, p < .001)] were best correlated with proprioceptive deficits in the sagittal plane; 2) injuries were correlated (p < .05) with proprioceptive deficits in the coronal (r = .22) and sagittal planes (r = .17) and with deficits in multiple planes (r = .19); 3) proprioceptive asymmetries were associated with injuries; and 4) the factor most highly correlated with the history of low back injuries was the presence of a spinal disorder (r = .40, p < .001). Impaired proprioception resulting from injury may degrade lumbar motor function, increasing workers' risk of reinjury. Restoring proprioception of the lumbar spine after injury should be a goal of treatment.

Adult↗
PubMed1990

The binocular representation of uniform motion.

In the model of motion perception proposed by Swanston, Wade, and Day (1987, Perception 16 143-159) it was suggested that retinocentric motion and eye movement information are combined independently for each eye, to give left and right orbitocentric representations of movement. The weighted orbitocentric values are then added, to give a single agocentric representation. It is shown that for a physical motion observed without pursuit eye movements this formulation predicts a reduction in the perceived extent of motion with monocular as opposed to binocular viewing. This prediction was tested, and shown to be incorrect. Accordingly, a modification of the model is proposed, in which the left and right retinocentric signals are weighted according to the presence or absence of stimulation, and combined to give a binocular retinocentric representation. In a similar way left-eye and right-eye position signals are combined to give a single binocular eye movement signal for version. This is then added to the binocular retinocentric signal to give the egocentric representation. This modification provides a unified account of both static visual direction and movement perception.

Attention↗
PubMedDate not supplied

Perception of horizontal head and trunk rotation in patients with loss of vestibular functions.

In patients with loss of vestibular functions, we studied psychophysically the self-motion perception for 'trunk in space' and 'head in space' during various combinations of horizontal head and trunk rotation in the dark. The results were compared to those of normal subjects. For their 'trunk in space' perception, the subjects relied on their internal image of space, derived from the vestibular receptors in the head, and referred their trunk to this as a reference by adding to it a nuchal trunk-to-head signal. The patients, by contrast, always considered the trunk as stationary. Obviously because they were devoid of any space cues, they abandoned or suppressed a neck contribution to their 'trunk in space' perception, which, in fact, would yield an erroneous perception in almost all conditions in the dark. Both the patients and the subjects based their 'head in space' perception on their internal representation of 'trunk in space' and added to this a nuchal head-to-trunk signal. However, the patients' head-to-trunk signal, unlike that of the subjects, was considerably larger than the actual head-to-trunk rotation at low stimulus frequency. We relate this finding to some unconscious modification of their neck muscle activity during passive head rotation. It appears that the patients' gain of the neck input per se is not increased, but rather that subsets of this input are modified according to the particular function they serve.

Adolescent↗
PubMed1996

Precise assessment of the mean effective luminance of texture patches--an approach based on reverse-phi motion.

In studying the response of mechanisms to contrast-defined texture stimuli, it is critical that the average effective luminance of these textures be equal to that of the background, to minimize net luminance-based signals. We present an efficient and accurate technique for constructing such equiluminant textures to isolate contrast-sensitive mechanisms for investigating their properties. The technique is based on the reverse-phi motion phenomenon, and the resulting settings agree closely with those obtained by photometric means for the class of textures studied. The method also allows one to explore the properties of contrast- and luminance-driven motion mechanisms and, in particular, to evaluate the contribution of putative second-order mechanisms to the motion percept. Results of applying the method are presented, and its advantages over the minimum-flicker and minimum-motion techniques are discussed.

Humans↗
PubMed2002

Activity patterns in human motion-sensitive areas depend on the interpretation of global motion.

Numerous imaging studies have contributed to the localization of motion-sensitive areas in the human brain. It is, however, still unclear how these areas contribute to global motion perception. Here, we investigate with functional MRI whether the motion-sensitive area hMT+/V5 is involved in perceptual segmentation and integration of motion signals. Stimuli were overlapping moving gratings that can be perceived either as two independently moving, transparent surfaces or as a single surface moving in an intermediate direction. We examined whether motion-sensitive area hMT+/V5 is involved in mediating the switches between the two percepts. The data show differential activation of hMT+/V5 with perceptual switches, suggesting that these are associated with a reconfiguration of cell assemblies in this area.

Brain↗
PubMed2003

Visual processing of coherent rotation in the central visual field: an fMRI study.

Functional magnetic resonance imaging was used to determine the brain areas that process coherent motion. To reduce the activity related to eye-movement planning and self-motion perception, rotation was used as coherent motion and the stimulus was restricted to the central visual field. Coherent rotation relative to incoherent random-dot motion resulted in consistent activation in the superior parietal lobule (SPL), in the lateral occipital gyrus (presumptive kinetic occipital region, KO), and in the fusiform gyrus (FG). The main novel finding in present study is the bilateral SPL activation, which has not been found in any previous study contrasting coherent and incoherent motion. It is suggested that the SPL activation is related to form-from-motion processing. The stimulus modification that prevented abrupt appearances of dots at the borders of the stimulus field increased the strength of rolling disk-like percept of the coherent stimulus. This perception of form may also be at least partly responsible for the activation in KO and FG. With this explanation, our three consistent activation areas are in line with previous findings. Furthermore, these results demonstrate that even delicate changes in some stimulus aspects can lead to significant changes in the activation of the brain.

Adult↗
PubMed1975

Perception and extrapolation of velocity and acceleration.

A moving target disappeared behind a screen and subjects predicted when the target passed behind a marker on the screen. When the target moved with constant velocity, predictions were extremely accurate, regardless of the spatial and temporal exposure and concealment of the target and regardless of its rate of velocity. When the target accelerated, accuracy of prediction decreased with increasing acceleration and with increasing target concealment. Analyses of the results suggest that the perception of velocity and acceleration is direct and accurate and that extrapolation of velocity and acceleration incorporates concrete and abstract characteristics of the motion that was seen. It is proposed that the motion perception system is tuned to accelerated rather than to constant velocity movement.

Acceleration↗
PubMed1989

Reaction times to motion onset and motion detection thresholds reflect the properties of bilocal motion detectors.

Several different psychophysical paradigms are used to study human motion perception. A unifying framework for the interpretation of all data is lacking. As a step towards a universal model for motion detection we show that previously published reaction times to motion onset and thresholds for the detection of periodic motion may be derived from the velocity dependent properties of bilocal motion detectors of the Reichardt correlator type. Thus, these data sets seem to support the concept of bilocal motion detectors.

Humans↗