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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↗

PubMed1999

Optokinetic nystagmus with spontaneous reversal of transparent motion perception.

When two visual patterns moving in opposite directions are superimposed, they appear to be at different depths and to slide over each other. Because the stimulus does not specify the depth-order between the surfaces, this transparent motion perception is essentially ambiguous. With prolonged observation, the perceived depth-order of the two moving surfaces reverses spontaneously. In the present study, the correlation between the perceived direction of transparent motion and optokinetic nystagmus (OKN) was examined. While viewing superimposed random-dot patterns moving in opposite horizontal or vertical directions, subjects attempted to fixate the center of the stimulus, while paying attention to either the near or far depth plane, and reported any changes of the direction of surface-motion at the attended depth. Even with attention focused on a particular depth, the spontaneous reversal of transparent motion perception still occurred. This indicates that the perceptual reversal may reflect a preattentive mechanism for depth-from-motion. Furthermore, the OKN slow-phase tended to be in the same direction as the perceived motion of the surface at the attended depth. These results support the idea that the mechanisms for OKN maintenance are sensitive to perception of depth-from-motion and, therefore, cortically mediated.

Adult↗

PubMed2000

The functional neuroanatomy of implicit-motion perception or representational momentum.

BACKGROUND: When we view static scenes that imply motion - such as an object dropping off a shelf - recognition memory for the position of the object is extrapolated forward. It is as if the object in our mind's eye comes alive and continues on its course. This phenomenon is known as representational momentum and results in a distortion of recognition memory in the implied direction of motion. Representational momentum is modifiable; simply labelling a drawing of a pointed object as 'rocket' will facilitate the effect, whereas the label 'steeple' will impede it. We used functional magnetic resonance imaging (fMRI) to explore the neural substrate for representational momentum. RESULTS: Subjects participated in two experiments. In the first, they were presented with video excerpts of objects in motion (versus the same objects in a resting position). This identified brain areas responsible for motion perception. In the second experiment, they were presented with still photographs of the same target items, only some of which implied motion (representational momentum stimuli). When viewing still photographs of scenes implying motion, activity was revealed in secondary visual cortical regions that overlap with areas responsible for the perception of actual motion. Additional bilateral activity was revealed within a posterior satellite of V5 for the representational momentum stimuli. Activation was also engendered in the anterior cingulate cortex. CONCLUSIONS: Considering the implicit nature of representational momentum and its modifiability, the findings suggest that higher-order semantic information can act on secondary visual cortex to alter perception without explicit awareness.

Adult↗

PubMed2001

Three-systems theory of human visual motion perception: review and update.

Lu and Sperling [Vision Res. 35, 2697 (1995)] proposed that human visual motion perception is served by three separate motion systems: a first-order system that responds to moving luminance patterns, a second-order system that responds to moving modulations of feature types-stimuli in which the expected luminance is the same everywhere but an area of higher contrast or of flicker moves, and a third-order system that computes the motion of marked locations in a "salience map," that is, a neural representation of visual space in which the locations of important visual features ("figure") are marked and "ground" is unmarked. Subsequently, there have been some strongly confirmatory reports: different gain-control mechanisms for first- and second-order motion, selective impairment of first- versus second- and/or third-order motion by different brain injuries, and the classification of new third-order motions, e.g., isoluminant chromatic motion. Various procedures have successfully discriminated between second- and third-order motion (when first-order motion is excluded): dual tasks, second-order reversed phi, motion competition, and selective adaptation. Meanwhile, eight apparent contradictions to the three-systems theory have been proposed. A review and reanalysis here of the new evidence, pro and con, resolves the challenges and yields a more clearly defined and significantly strengthened theory.

Contrast Sensitivity↗

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↗

PubMed2001

Transducer models of head-centred motion perception.

By adding retinal and pursuit eye-movement velocity one can determine the motion of an object with respect to the head. It would seem likely that the visual system carries out a similar computation by summing extra-retinal, eye-velocity signals with retinal motion signals. Perceived head-centred motion may therefore be determined by differences in the way these signals encode speed. For example, if extra-retinal signals provide the lower estimate of speed then moving objects will appear slower when pursued (Aubert-Fleischl phenomenon) and stationary objects will move opposite to an eye movement (Filehne illusion). Most previous work proposes that these illusions exist because retinal signals encode retinal motion accurately while extra-retinal signals under-estimate eye speed. A more general model is presented in which both signals could be in error. Two types of input/output speed relationship are examined. The first uses linear speed transducers and the second non-linear speed transducers, the latter based on power laws. It is shown that studies of the Aubert-Fleischl phenomenon and Filehne illusion reveal the gain ratio or power ratio alone. We also consider general velocity-matching and show that in theory matching functions are limited by gain ratio in the linear case. However, in the non-linear case individual transducer shapes are revealed albeit up to an unknown scaling factor. The experiments show that the Aubert-Fleischl phenomenon and Filehne illusion are adequately described by linear speed transducers with a gain ratio less than one. For some observers, this is also the case in general velocity-matching experiments. For other observers, however, behaviour is non-linear and, according to the transducer model, indicates the existence of expansive non-linearities in speed encoding. This surprising result is discussed in relation to other theories of head-centred motion perception and the possible strategies some observers might adopt when judging stimulus motion during an eye movement.

Eye Movements↗

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↗

PubMed2002

Conditions under which stereopsis and motion perception are blind.

We describe modified random-dot stereograms in which the corresponding elements differ from non-corresponding elements in colour, size, and luminance. Despite these visible differences between the elements, depth perception collapses when the spatially integrated luminous flux is similar for the corresponding and non-corresponding elements. Our results suggest that a low-pass spatial filter precedes the mechanism that recognises disparity. A similar phenomenon is observed for the perception of coherent motion in random-dot kinematograms. Our modified stereograms and kinematograms may find other uses when experimenters wish to study the contribution of colour to visual processes and require a method of eliminating edge artifacts.

Adult↗

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↗