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PubMed1995

[Motion discrimination as as test for visual motion perception].

Recent neurophysiological studies have indicated that there are two parallel pathways in vision processing independently shape and motion. There are many methods for examining perception of color and shape, but none for examining visual motion perception. In this study, we devised a "motion discrimination task (MDT)" for evaluating motion perception, which was displayed on a computer monitor, and recorded normal responses to the MDT in 90 normal subjects. Responses to MDT were not affected by visual acuity, but were affected by dot speed of the MDT. There was little trial-to-trial or subject variability in the MDT. These findings indicate that our MDT is a good clinical test for evaluating motion perception in human subjects.

Adolescent↗
PubMed1993

The effects of background visual roll stimulation on postural and manual control and self-motion perception.

The effects of background visual roll stimulation on postural control, manual control, and self-motion perception were investigated in this study. In the main experiment, 8 subjects were exposed to wide field-of-view background scenes that were tilted and static, continuously rotating, or sinusoidally rotating at frequencies between 0.03 and 0.50 Hz, as well as a baseline condition. The subjects performed either a postural control task (maintain an upright stance) or a manual control task (keep an unstable central display horizontally level). Root-mean square (RMS) error in both the postural and manual control tasks was low in the static tilt condition and extremely high in response to continuous rotation. Although the phases of the postural and manual responses were highly similar, the power and RMS error generated by the sinusoidal visual background stimulation peaked at a lower frequency in the postural task. Vection ratings recorded at the end of the postural and manual trials somewhat paralleled the frequency tuning differences between tasks, which a subsequent experiment showed to be the result of the differential motion of the central display rather than the differential positioning of the subject. In general, these results show that the dynamic characteristics of visual orientation systems vary according to the specific motor and/or perceptual system investigated.

Adult↗
PubMed1995

Eye movements and motion perception induced by off-vertical axis rotation (OVAR) at small angles of tilt after spaceflight.

The nystagmus and motion perception of two astronauts were recorded during Earth-vertical axis rotation and during off-vertical axis rotation (OVAR) before and after 7 days of spaceflight. Postflight, the peak velocity and duration of per- and postrotatory nystagmus during velocity steps about the Earth-vertical axis were the same as preflight values. During OVAR at constant velocity (45/s, tilt angles successively 5, 10, and 15 degrees), the mean horizontal slow-phase eye velocity (bias), produced by the 'velocity storage mechanism' in the vestibular system, and the peak-to-peak amplitude (modulation) in horizontal eye velocity and position, generated from the output of otolith afferents, were also the same before as after flight. There were, however, changes in the vertical eve position and in the perceived body motion during OVAR. The angle of the perceived body path described as a cone was larger in both astronauts postflight. One astronaut experienced either a large cone angle with its axis upright, or a smaller cone angle with its axis tilted backwards, accompanied by an upward vertical eye drift. These results suggest an increase in the sensitivity of the otolithic system after spaceflight and a longer period of readaptation to Earth's gravity for otolith-induced responses than for canal-induced responses. Our data support the hypothesis that just after spaceflight the CNS generally interprets changes in the otolith signals to be due to translation rather than to tilt.

Eye Movements↗
PubMed1998

Age-related deterioration of motion perception and detection.

PURPOSE: The purpose of this study was to evaluate the effect of aging on motion detection and perception. METHODS: Forty-six subjects, ages 19-92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick. RESULTS: Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction. CONCLUSION: The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.

Adult↗
PubMed1997

[The objective evaluation of the interaction between color vision and motion perception].

PURPOSE: To measure equiluminance values of green/red grating luminosity ratios with different moving velocity in normal subjects and to explore the interaction between color vision and motion perception. METHODS: Optokinetic nystagmus (OKN) of eye movement elicited by moving color grating stimulus could be recorded with electrooculograph (EOG). The equiluminance points were determined when OKN changed in direction in various moving velocities. Sixteen cases (32 eyes) normal subjects were tested, 6 cases male and 10 cases female, Age ranged from 20 to 51 years old. RESULTS: The mean equiluminance points were 0.525, 0.425, 0.397, 0.391, 0.367 under 595, 400, 301, 239 and 200 mm/s groups of grating moving velocity respectively. There were statistically significant differences of mean equiluminance points among 595 mm/s group and other groups (P < 0.01), there were no statistically significant differences of mean equiluminance points among other 4 groups (P > 0.05). CONCLUSION: There are some influences to color vision under the high moving condition.

Adult↗
PubMed1998

Effect of eye movements on the magnitude of functional magnetic resonance imaging responses in extrastriate cortex during visual motion perception.

We have studied the effects of pursuit eye movements on the functional magnetic resonance imaging (fMRI) responses in extrastriate visual areas during visual motion perception. Echoplanar imaging of 10-12 image planes through visual cortex was acquired in nine subjects while they viewed sequences of random-dot motion. Images obtained during stimulation periods were compared with baseline images, where subjects viewed a blank field. In a subsidiary experiment, responses to moving dots, viewed under conditions of fixation or pursuit, were compared with those evoked by static dots. Eye movements were recorded with MR-compatible electro-oculographic (EOG) electrodes. Our findings show an enhanced level of activation (as indexed by blood-oxygen level-dependent contrast) during pursuit compared with fixation in two extrastriate areas. The results support earlier findings on a motion-specific area in lateral occipitotemporal cortex (human V5). They also point to a further site of activation in a region approximately 12 mm dorsal of V5. The fMRI response in V5 during pursuit is significantly enhanced. This increased response may represent additional processing demands required for the control of eye movements.

Adult↗
PubMed2000

Attentional modulation of visual motion perception.

How is the perception and processing of visual motion affected by attention? This review examines recent research in cognition, perception and neurophysiology that explores how ongoing behavioural tasks (and the attentional states they impose) modulate the processing of visual motion. Although traditional views hold that motion is processed in an obligatory, 'pre-attentive' manner, evidence for processing in a task-independent manner is scant. Recent studies of human perception that have measured motion priming, motion aftereffects, uncertainty effects, and motion-interaction effects indicate instead that even simple aspects of motion processing may be substantially affected by whether motion information in a task is used or ignored by the perceiver. Single-unit studies in brain areas sensitive to visual motion in monkeys, and functional imaging studies on humans, also indicate that task and attentional state affect activity levels in brain regions thought to be important in motion perception. This review brings together these converging findings of attentional modulation of motion perception and considers them in light of object-oriented theories of attention.

Journal Article↗
PubMed1981

The spatial and temporal organisation of motion perception units in human vision.

Measurements of threshold illumination levels for detection of retinally non-localised moving targets show that detection of a moving target is influenced by both the spatial and the temporal modulation of the background field. The temporal response characteristics obtained from these measurements are similar to those obtained from experiments on detection of temporal flicker. Experiments with spatially modulated background fields reveal visual mechanisms with spatial properties which are essentially independent of many stimulus parameters. The response amplitude of the spatial filter which characterises these mechanisms increases linearly as a function of background contrast and is independent of the relative orientation between the background structure and the direction of target movement. These properties are used to compute the two-dimensional spatial characteristics of mechanisms involved in the detection of moving targets.

Adult↗
PubMed1993

Apparent motion perception: the contribution of the binocular and monocular systems. An improved test based on motion aftereffects.

Research concerning the perception of apparent motion is not easy to conduct: it is hard to obtain quantitative results that can be easily interpreted. A solution to this problem is the use of motion aftereffects (MAEs). Adapting subjects to a specific type of motion leads to apparent motion in the opposite direction when the stimulus is removed. However, subjects are aware of the change in stimulus conditions. A new dynamic test stimulus is proposed in order to avoid artefacts introduced by the awareness of the conditions by the subject. A model, derived from earlier observations, is described which includes contributions from monocular and binocular systems. Results from an experiment in which the dynamic test stimulus was used show that they do not necessarily reproduce the results obtained with a static test stimulus. Central monocular systems are added to the model to account for this discrepancy. The 'pooling hypothesis', which states that the MAE is a weighted mean of the processes involved, permits the estimation of the weights of the individual subsystems. The results of the experiments are explained in terms of this hypothesis by the new model.

Adaptation, Ocular↗
PubMedDate not supplied

Delay of pattern electroretinogram peaks and its correlation to contrast threshold for motion perception in glaucoma.

Peak latencies of pattern electroretinogram (PERG) were compared between glaucomatous eyes and non-glaucomatous eyes. Contrast threshold for motion perception (CTMP) was also measured with a new device in addition to routine static contrast sensitivity, static visual field and visual acuity. In the present recording, configurations for PERG, i.e. low reversal rate, low mean luminance and presence of background illumination, the PERG peak and trough (P1 and N2, respectively) latencies, were significantly prolonged in the glaucomatous eyes. Although both of the two PERG latencies were strongly correlated with the CTMP, only the P1 peak latency was strongly correlated with the perimetric indices. These results suggest that the P1 and N2 latencies reflect different aspects of signal processing in the retina, especially for moving targets.

Adolescent↗
PubMed1994

Motion perception and Alzheimer's disease.

The motion sensitivity of 15 probable Alzheimer disease (AD) patients and 15 healthy elderly adults was investigated with a correlated motion paradigm. The AD patients exhibited significantly higher thresholds for detecting the direction of motion. Contrast sensitivity for a 2 cpd, 7.5 Hz counterphased stimulus was related to motion threshold in the AD group. There also was a significant relationship between an index of dementia severity, Mini-Mental State Exam (MMSE), and motion sensitivity. The results support the hypothesis proposed from neuroanatomical evidence by Hof and Morrison (1990) that AD results in a disruption of the visual signals mediated by area 17. Further, the data suggest that this disruption of visual processing is linked to the progression of dementia. The study offers support for the hypothesis that AD leads to a deficit in the magnocellular or M pathway of visual processing.

Aged↗
PubMed1992

Insect motion perception.

The first step in this work of reconstruction of a theory of insect vision was to demonstrate that visual behaviour relies on scanning by self-motion and apparently involves measurement of angular velocities of contrasts moving across the eye. The next step was to demonstrate that parallax is also significant as a way of segmenting the visual scene into separate objects. There followed a series of experiments to rule out the existing theory that motion perception depends on autocorrelation, and at the same time an alternative theory was developed. The new theory assumes that at the level of the optic medulla there are numerous parallel channels on each visual axis, representing different neurons, all looking out for their specific combination of signals. The combinations are formed by positive, negative or no-change temporal contrasts at two adjacent visual axes at two successive times, forming 3(4) = 81 possible templates. Simulation of this highly parallel system shows that it can represent the moving image in a compact form that would be adequate to explain what is known for motion and form vision (but not colour vision) in insects. Form, like colour, would be seen as the ratio of numbers of responses of particular templates, in the same way that colours are seen as ratios of responses of receptors for different wavelengths.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1985

A model for direction selectivity in threshold motion perception.

Thresholds were measured for a moving line superimposed on moving sinusoidal gratings. When line and grating moved in the same direction significant subthreshold summation was observed over a range of spatial frequencies. For motion of the line and grating in opposite directions, summation was never observed. This supports the hypothesis that direction selective mechanisms are responsible for motion perception at threshold. Further analysis of the data produced estimates of the spatial frequency tuning of these mechanisms. A quantitative model is proposed to interpret the data, and it is suggested that flickering gratings are not decomposed into their moving components by the visual system.

Cybernetics↗
PubMed1993

Neural dynamics of motion perception: direction fields, apertures, and resonant grouping.

A neural network model of global motion segmentation by visual cortex is described. Called the motion boundary contour system (BCS), the model clarifies how ambiguous local movements on a complex moving shape are actively reorganized into a coherent global motion signal. Unlike many previous researchers, we analyze how a coherent motion signal is imparted to all regions of a moving figure, not only to regions at which unambiguous motion signals exist. The model hereby suggests a solution to the global aperture problem. The motion BCS describes how preprocessing of motion signals by a motion oriented contrast (MOC) filter is joined to long-range cooperative grouping mechanisms in a motion cooperative-competitive (MOCC) loop to control phenomena such as motion capture. The motion BCS is computed in parallel with the static BCS of Grossberg and Mingolla (1985a, 1985b, 1987). Homologous properties of the motion BCS and the static BCS, specialized to process motion directions and static orientations, respectively, support a unified explanation of many data about static form perception and motion form perception that have heretofore been unexplained or treated separately. Predictions about microscopic computational differences of the parallel cortical streams V1-->MT and V1-->V2-->MT are made--notably, the magnocellular thick stripe and parvocellular interstripe streams. It is shown how the motion BCS can compute motion directions that may be synthesized from multiple orientations with opposite directions of contrast. Interactions of model simple cells, complex cells, hyper-complex cells, and bipole cells are described, with special emphasis given to new functional roles in direction disambiguation for endstopping at multiple processing stages and to the dynamic interplay of spatially short-range and long-range interactions.

Animals↗
PubMed2000

Effects of glaucoma and aging on photopic and scotopic motion perception.

PURPOSE: To examine the effects of primary open-angle glaucoma and normal aging on visual sensitivity for targets known to bias responses from the magnocellular visual processing stream. METHODS: Contrast sensitivity was measured for the detection and direction discrimination of low-spatial-frequency (0.5 cyc/deg), drifting (4-24 Hz) sinusoidal gratings in 15 patients with glaucoma (mean age, 58.7 years), 14 age-matched control subjects (mean age 55.8 years), and 10 young control subjects (mean age, 24.4 years). As a control, sensitivity was measured for the detection of stationary stimuli. Stimuli of 4.7 degrees square were presented at either 0 degrees eccentricity or at 20 degrees along the nasal horizontal meridian, under both photopic and scotopic levels of lighting. RESULTS: Across a wide range of conditions, the ability to detect and discriminate visual motion declined significantly (P < 0.05) with increasing age, whereas the ability to detect stationary patterns was generally unaffected. The rate of decline was adequately described by a simple linear function. Control studies showed that the age-related motion sensitivity losses could not be attributed solely to decreases in retinal illuminance associated with increasing age. Of note, however, there were no significant differences in mean sensitivity between glaucoma and age-matched control groups for any of the conditions used. CONCLUSIONS: Even under conditions believed to bias the response of the visual system to the magnocellular pathway, glaucoma subjects could not be reliably differentiated from control subjects on the basis of mean sensitivity to motion stimuli. The findings have two broad implications: first, that substantial neural loss specific for motion perception occurs during the processes of normal aging, and second, that sensitivity to motion targets per se may not be a useful indicator of neural integrity in the early stages of glaucoma.

Adult↗