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PubMed1999

The mechanism of isoluminant chromatic motion perception.

An isoluminant chromatic display is a color display in which the component colors have been so carefully equated in luminance that they stimulate only color-sensitive perceptual mechanisms and not luminance-sensitive mechanisms. The nature of the mechanism by which isoluminant chromatic motion is perceived is an important issue because color and motion processing historically have been associated with different neural pathways. Here we show that isoluminant chromatic motion (i) fails a pedestal test, (ii) has a temporal tuning function that declines to half-amplitude at 3-6 Hz, and (iii) is perceived equally well when the entire motion sequence is presented monocularly (entire motion sequence to one eye) versus interocularly (the frames of motion sequence alternate between eyes so that neither eye individually could perceive motion). These three characteristics indicate that chromatic motion is detected by the third-order motion system. Based on this theory, it was possible to take a moving isoluminant red-green grating and, by simply increasing the chromatic contrast of the green component, to generate the full gamut of motion percepts, from compelling smooth motion to motion standstill. The perception of motion standstill when the third-order mechanism is nullified indicates that there is no other motion computation available for purely chromatic motion. It follows that isoluminant chromatic motion is not computed by specialized chromatic motion mechanisms within a color pathway but by the third-order motion system at a brain level where binocular inputs of form, color, depth, and texture are simultaneously available and where selective attention can exert a major influence.

Calibration↗
PubMed1995

The functional architecture of human visual motion perception.

UNLABELLED: A powerful paradigm (the pedestal-plus-test display) is combined with several subsidiary paradigms (interocular presentation, stimulus superpositions with varying phases, and attentional manipulations) to determine the functional architecture of visual motion perception: i.e. the nature of the various mechanisms of motion perception and their relations to each other. Three systems are isolated: a first-order system that uses a primitive motion energy computation to extract motion from moving luminance modulations; a second-order system that uses motion energy to extract motion from moving texture-contrast modulations; and a third-order system that tracks features. Pedestal displays exclude feature-tracking and thereby yield pure measures of the first- and second-order systems which are found to be exclusively monocular. Interocular displays exclude the first- and second-order systems and thereby to yield pure measures of feature-tracking. RESULTS: both first- and second-order systems are fast (with temporal frequency cutoff at 12 Hz) and sensitive. Feature tracking operates interocularly almost as well as monocularly. It is slower (cutoff frequency is 3 Hz) and it requires much more stimulus contrast than the first- and second-order systems. Feature tracking is both bottom-up (it computes motion from luminance modulation, texture-contrast modulation, depth modulation, motion modulation, flicker modulation, and from other types of stimuli) and top-down--e.g. attentional instructions can determine the direction of perceived motion.

Attention↗
PubMed1987

Influence of head or trunk oscillations on visually induced self-motion perception in humans.

The influence of concurrent head or trunk movements on optokinetically induced self-motion perception has been investigated by measuring circularvection (CV) latencies. Active head as well as passive trunk oscillation cause an increase in circularvection latency of about 50% as compared to latencies with the head and trunk stationary during full field optokinetic stimulation. The results point towards an intersensory inhibition of self-motion perception.

Adolescent↗
PubMed1998

First- and second-order motion perception in Gabor micropattern stimuli: psychophysics and computational modelling.

This paper examines the perception of first- and second-order motion in human vision. In an extension of previous work by Boulton and Baker [J.B. Boulton, C.L. Baker, Motion detection is dependent on spatial frequency not size, Vision Res., 31 (1991) 77-87; J.B. Boulton, C.L. Baker, Different parameters control motion perception above and below a critical density, Vision Res., 33 (1993) 1803-1811], the direction of two-frame apparent motion is measured for stimuli composed of Gabor or Gaussian micropatterns. Three conditions are investigated. Condition 1 is that used by Boulton and Baker, in which motion is defined by the displacement of Gabor micropatterns. In condition 2, motion is defined by the displacement of Gaussian micropatterns. In condition 3, the envelopes of Gabor micropatterns are displaced while their carriers remain static. Using sparsely distributed micropatterns, direction judgements in all three conditions are determined by the spacing of the micropatterns. With a dense stimulus, direction judgements vary as a function of displacement in qualitatively different ways for the three conditions. The psychophysical results are predicted by a two-channel computational model. In one channel, motion is calculated directly from stimulus luminance, while in the other it is preceded by a texture-grabbing operation. The relative activities of the two channels dictates which governs direction judgements for any given stimulus.

Computer Simulation↗
PubMed1990

Consequences of spatial sampling for human motion perception.

This paper describes evidence for spatial aliasing in human motion perception. For a certain range of spatial frequencies, interference fringes drifting across the extrafoveal retina resemble two-dimensional spatial noise drifting in the opposite direction. For retinal locations within 10 deg of the fovea, the perceived direction of motion is veridical up to spatial frequencies near the cone Nyquist frequency, reverses between one and two times the cone Nyquist frequency, and sometimes reverses back to the correct direction at still higher frequencies. Thus two "motion nulls", or spatial frequencies at which the direction of motion is ambiguous, are typically observed at each retinal eccentricity. A computational model is described in which sinusoidal gratings are sampled by a cone mosaic and the direction of motion of the filtered output is computed. The model predicts that the second motion null, but not the first, should be relatively immune to postreceptoral processing and should roughly equal twice the cone Nyquist frequency. This prediction is confirmed by psychophysical experiments, providing a new technique to estimate cone spacing in the living human eye.

Discrimination, Psychological↗
PubMed1995

Motion perception deficits in glaucomatous optic neuropathy.

The mechanisms mediating impaired motion perception in glaucoma were investigated. Direction discrimination thresholds for low (4.2 deg/sec) and high (12.5 deg/sec) velocity random-dot kinematograms were measured in controls and patients with glaucoma or ocular hypertension. Thresholds were elevated significantly in glaucoma patients and individual ocular hypertensives. Threshold elevations were not due to blur or pupil size. After compensating for motion reversals, high but not low velocity thresholds remained elevated. Only high velocity thresholds correlated with differential luminance sensitivity. A hypothesis that different mechanisms mediate glaucoma-induced deficits at high and low velocities is presented.

Adult↗
PubMed1997

[The test of motion perception in normal subjects].

OBJECTIVE: To study the properties of motion perception (MP) of normal Chinese subjects. METHOD: MPs were tested for 56 cases (112 eyes) of normal subjects, their ages ranging from 11 years to 68 years, by using vertical moving bars generated on VGA monitor in a PC compatible computer. RESULTS: MPs were affected by age when the bars moved horizontally for 2 pixels, the ratios of MP were increased with age growing from 10 year group to 30 year group, then the ratios of MP were gradually decreased from 40 year group. MPs were not affected by age under the horizontally moving conditions of 4 pixels and 6 pixels and > 40 Hz flicker movement. There were no relationships between either MP and sex or MP and eye side difference. CONCLUSIONS: The characteristics of MP are determined and the normal reference values are provided in normal Chinese subjects.

Adolescent↗
PubMed1993

Motion perception during saccades.

Although the retinal image is displaced by each saccade performed we do not perceive the visual environment moving concordant with the saccades. In this study experiments were designed in which additional movement of most of the visual scene was applied during saccades. The subjects perceived the intrasaccadic movement after the saccade. The perceived speed of this movement was decreased and the threshold amplitude was increased compared to perception during fixation. The intrasaccadic movement perception was based on a novel aftereffect of motion perception. The velocity of retinal slip did not affect the threshold. If the retinal slip speed during saccades was temporally reduced by an intrasaccadic movement parallel to the saccade, the threshold amplitude was identical to the threshold amplitude obtained by intrasaccadic movement opposite to the saccade increasing retinal slip speed. Horizontal intrasaccadic movements were detected at lower thresholds than vertical movements independent of saccade direction. In addition, the thresholds were not effected by the saccade amplitude suggesting that neither speed, duration, nor direction of eye movement related retinal slip affects the amount of suppression. Our results suggest that saccadic suppression is related to delayed central processing of retinal information during saccades. This processing does not involve saccade parameters such as direction and amplitude.

Adult↗
PubMed1998

The test of motion perception of the normal Chinese subjects.

OBJECTIVE: To investigate the characteristic of motion perception (MP) of normal Chinese subjects. METHODS: MPs were recorded from 56 normal subjects (112 eyes), age ranged from 11 to 68 years, and the MP software was controlled by PC compatible computer which appeared as the vertical bar targets in VGA screen. RESULTS: The Mp rates were ascending gradually from 10 age-group to 30 age-group as the age increased in the 2 pixels (2P) horizontal motion, and the MP rates were decreasing gradually over 40 age-group, and the MP rates were not affected by the age in the 4 pixels (4P), 6 pixels (6P) horizontal motion and > 40 Hz flick motion. There was no relation between the MP and the sex and the different eyes. CONCLUSIONS: The characteristic of MP of the normal Chinese subjects was determined and the results provided the normal reference values.

Adolescent↗
PubMed1995

Development of motion perception in early infancy.

This article summarizes some research on the development of motion perception in early infancy. The sensitivity for slow and rapid motion was studied with 1-month-old and 3-month-old babies. The findings suggest that there are different developmental courses for the detection of slow and rapid motion. The ability to detect very slow motion seems to improve gradually with age whereas the sensitivity for very rapid motion seems to be at a level comparable to adults soon after birth. Three-month-old babies do use kinetic visual information in order to perceive object boundaries and form. After having seen a form visible only when moving they are able to "identify" the same form when seeing it under static conditions. Infants and young children do use kinetic visual information for recognizing figures that are never completely in sight only if they have been familiarized with the fully visible form first. Even 4-year-olds have difficulties in perceiving the full form of a figure that moves behind a slit in an opaque occluding surface if there is no familiarity or "priming" with the global form first. In conclusion, infants are able to detect visual motion very early in life and do extract information which leads to the perception of form. However, this ability may be limited to events with uninterrupted, continuous movement of visible elements.

Age Factors↗
PubMed1996

The shape of self-motion perception--I. Equivalence classification for sustained motions.

Two completely different motions of a subject relative to the earth can induce exactly the same stimuli to the vestibular, somatosensory and visual systems. When this happens, the subject may experience disorientation and misperception of self-motion. We have identified large classes of motions that are perceptually equivalent, i.e. indistinguishable by the subject, under three sets of conditions: no vision, with vision and earth-fixed visual surround, and with vision during possible movement of the visual surround. For each of these sets of conditions, we have developed a classification of all sustained motions according to their perceptual equivalences. The result is a complete list of the possible misperceptions of sustained motion due to equivalence of the forces and other direct stimuli to the sensors under the given conditions. This research expands the range of possible experiments by including all components of linear and angular velocity and acceleration. Many of the predictions in this paper can be tested experimentally. In addition, the equivalence classes developed here predict perceptual phenomena in unusual motion environments that are difficult or impossible to investigate in the laboratory.

Humans↗
PubMed1997

Constant affine velocity predicts the 1/3 power law of planar motion perception and generation.

Numerous studies have shown that the power of 1/3 is important in relating Euclidean velocity to radius of curvature (R) in the generation and perception of planar movement. Although the relation between velocity and curvature is clear and very intuitive, no valid explanation for the specific 1/3 value has yet been found. We show that if instead of computing the Euclidean velocity we compute the affine one, a velocity which is invariant to affine transformations, then we obtain that the unique function of R which will give (constant) affine invariant velocity is precisely R1/3. This means that the 1/3 power law, experimentally found in the studies of hand-drawing and planar motion perception, implies motion at constant affine velocity. Since drawing/perceiving at constant affine velocity implies that curves of equal affine length will be drawn in equal time, we performed an experiment to further support this result. Results showed agreement between the 1/3 power law and drawing at constant affine velocity. Possible reasons for the appearance of affine transformations in the generation and perception of planar movement are discussed.

Analysis of Variance↗
PubMed1994

A reduction in the number of directionally selective neurons extends the spatial limit for global motion perception.

Dynamic random-dot targets were used to study neural mechanisms underlying motion perception. Performance of cats with severely reduced numbers of cortical directionally selective neurons (reduced DS) was compared to that of normal animals. We assessed the spatial properties of the residual motion mechanism by measuring direction discriminations at various dot displacements. At small displacements, reduced DS cats' motion integration thresholds for opposite direction discrimination were nearly normal. At larger displacements, their thresholds surpassed those of normal cats and their upper displacement limit (dmax) was increased by 0.35 deg. The accuracy of direction discrimination was reduced at small displacements, but at larger displacements direction difference thresholds of reduced DS cats approached or surpassed those of normals. These data were compared to the performance of humans who showed an extension of dmax for peripherally viewed targets. The data support the hypothesis that expansion in spatial scale of the motion mechanism may contribute to extension of dmax. Additional support for this hypothesis is provided by a modified direction discriminating line-element model. The model also suggests that changes in sampling of motion mechanisms in the reduced DS system may play a role.

Animals↗
PubMed1982

Motion perception in the peripheral visual field.

Literature dealing with the peripheral retina and its 'specialization for motion detection' is reviewed. The data at hand seem to indicate that the central retina is more 'specialized' for motion perception than the peripheral retina. It is clear that motion improves vision for stimuli presented peripherally.

Eye Movements↗
PubMedDate not supplied

A comparison of the latencies of visually induced postural change and self-motion perception.

This study compared the latencies of visually induced postural change and self-motion perception under identical visual conditions. The results showed that a visual roll stimulus elicits postural tilt in the direction of scene motion and an increase in postural instability several seconds before the subject begins to perceive illusory self-motion (vection) in the opposite direction. Postural and vection latencies correlate highly with one another, but bear little relationship with the magnitude of either sway or vection.

Adolescent↗
PubMed1998

Human motion perception and smooth eye movements show similar directional biases for elongated apertures.

Although numerous studies have examined the relationship between smooth-pursuit eye movements and motion perception, it remains unresolved whether a common motion-processing system subserves both perception and pursuit. To address this question, we simultaneously recorded perceptual direction judgments and the concomitant smooth eye-movement response to a plaid stimulus that we have previously shown generates systematic perceptual errors. We measured the perceptual direction biases psychophysically and the smooth eye-movement direction biases using two methods (standard averaging and oculometric analysis). We found that the perceptual and oculomotor biases were nearly identical, suggesting that pursuit and perception share a critical motion processing stage, perhaps in area MT or MST of extrastriate visual cortex.

Humans↗
PubMedDate not supplied

Cervico-vestibular and visuo-vestibular interaction. Self-motion perception, nystagmus, and gaze shift.

In 8 healthy subjects we studied self-motion perception and nystagmus due to sinusoidal stimulation (amplitude 90 degrees peak to peak, frequency 0.05 Hz) of the horizontal semicircular canals, the cervical proprioceptors, and the retina. We used an electrically driven rotatory chair and optokinetic drum combination. For cervical stimulation the subject's head was placed in a clamp, attached to the drum. Eye movements were recorded by means of electrooculography, d.c. amplification. Subjects signalled the estimated head position by means of a 'joystick'. In the present series of experiments the vestibular and cervical informations were played off against each other in combined stimulation conditions with an interstimulus phase lag of 0 to 315 degrees, in steps of 45 degrees. Similarly, the vestibular and visual informations were played off against each other. Concerning estimated head position, our main finding is that both the visually and the cervically induced illusion of head rotation overrule the vestibular sensation of head motion. The ocular response to combined vestibular plus cervical stimulation shows that both nystagmus slow phases and saccades of the cervical and the vestibular responses add up by vectorial summation.

Adult↗