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At least 19 recordsLinked to original sources
PubMed1987

Effects of proposed preflight adaptation training on eye movements, self-motion perception, and motion sickness: a progress report.

A program has been initiated to develop apparatus and procedures to preadapt astronauts to the sensory rearrangement associated with weightlessness in spaceflight. If space motion sickness is a consequence of adaptation to that sensory rearrangement, preflight training could afford astronauts significant relief from the motion sickness. The preflight adaptation trainer (PAT) was designed to produce rearranged relationships between visual and otolith signals analogous to those experienced in space. Investigations have been undertaken with three prototype trainers. The results indicated that exposure to the PAT sensory rearrangement altered self-motion perception, induced motion sickness, and changed the amplitude and phase of the horizontal eye movements evoked by roll stimulation. However, the changes were inconsistent. Appropriate measures of adaptation and protocols for producing the adaptation efficiently remain to be determined.

Adaptation, Physiological↗
PubMed2002

Motion perception and motion estimation by total-least squares.

A computational model of motion perception is proposed. The model, which is gradient-based, adheres to the neural constraint that transmitted signals are positive-valued functions by posing the estimation of image motion as a quadratic programming problem combined with total-least squares: a model that assumes that image signals are contaminated by noise in both the spatial and temporal dimensions. By shrinking motion estimates with a regularizer whose subtractive effect introduces a contrast dependent speed threshold into motion computations, it is shown that the total-least squares model when posed as a quadratic programming problem, is capable of explaining both increases and decreases in perceived speed as these effects were reported by Thompson (1982) to vary as a function of image contrast and temporal frequency. The correlation that exists between the model's contrast speed response and results reported from visual psychophysics is consistent with the view that the visual system assumes that image signals may be contaminated by noise in both the spatial and the temporal domain, and that visual motion is influenced by the consequence of these assumptions.

Humans↗
PubMed1998

Successive episodes produce direction contrast effects in motion perception.

Motion coherence thresholds decline with an increase in the number of frames in a random dot kinematogram (RDK), indicating that motion information can be integrated across successive frames. We investigated whether such temporal integration would be disrupted by a brief interval (32-600 msec) inserted into a motion sequence, perceptually dividing it into two successive episodes. Both episodes consisted of only a few frames (between 3 and 15), with the first episode being 100% coherent and the coherence of the second episode being adjusted to determine threshold. In four experiments we observed that coherence threshold for motion in the second episode was elevated if the directions in the two episodes matched, was lowered if they were opposite, and was unaffected if they were orthogonal. This successive direction contrast effect did not vary with the duration of the interval, suggesting that it is not an adaptation effect. The result of varying the number of frames in the second episode suggests that these effects are not due to alterations in cooperative activity among motion detectors. We suggest that successive direction contrast effects may reflect activity of higher-order perceptual organization mechanisms.

Adult↗
PubMed1993

Functional segregation of color and motion perception examined in motion nulling.

We examine two hypotheses about the functional segregation of color and motion perception, using a motion nulling task. The most common interpretation of functional segregation, that motion perception depends only on one of the three dimensions of color, is rejected. We propose and test an alternative formulation of functional segregation: that motion perception depends on a univariate motion signal driven by all three color dimensions, and that the motion signal is determined by the product of the stimulus contrast and a term that depends only on the relative cone excitations. Two predictions of this model are confirmed. First, motion nulling is transitive: when two stimuli null a third they also null another. Second, motion nulling is homogeneous: if two stimuli null one another, they continue to null one another when their contrasts are scaled equally. We describe how to apply our formulation of functional segregation to other behavioral and physiological measurements.

Color Perception↗
PubMed1997

Visual motion perception after brain damage: I. Deficits in global motion perception.

We report on the test results of a group of 32 mostly unilaterally brain-damaged patients examined for global visual motion perception. Three of these patients had severely impaired visual motion perception in their contralateral visual half-field, a deficit remarkably similar to the perceptual defects found in V5-lesioned monkeys. Two of these three patients had a right-hemisphere lesion; the remaining one had a left-hemisphere lesion. We conclude that both hemispheres of the human brain contain an area, functionally equivalent to V5, which subserves visual motion perception in the contralateral visual half-field. Lesion analysis revealed that this area is located in the posterior medial temporal gyrus.

Adult↗
PubMed1996

Object motion perception during ego-motion: patients with a complete loss of vestibular function vs. normals.

Object motion perception was assessed in avestibular patients and normal controls. Two experiments were conducted, in which subjects were required to assess the motion of a visual stimulus with respect to earth. In the first experiment, we measured the velocity at which a briefly presented (200 ms) grating was perceived as earth fixed, while the subject maintained fixation on a visual target fixed relative to the body, during whole-body yaw rotation (VOR suppression). In this experimental setup, the influence of the semicircular canal signals on object motion perception was evaluated. The avestibular patients judged the grating to be stationary with respect to earth, when it was moving at the same velocity as their body, whereas for normal controls, the grating was perceived as stationary when it moved at a velocity slower than their body motion, but greater than zero. The difference between the two subject groups was significant, and showed the strong contribution of the vestibular system to object motion perception. Similarly, a measurement of the velocity at which a grating was perceived as stationary was obtained during smooth pursuit eye movements. In this experiment the contribution of the efference copy of the oculomotor signal and proprioceptive signals to object motion perception were assessed. As with the first experiment, the normal controls displayed a more veridical sense of object motion perception than the patients, although the difference was only just significant. We suggest that the difference could be an adaptive change in the patients perception of motion, which allows them to reduce the effects of oscillopsia.

Humans↗
PubMed1997

Visual motion perception after brain damage: II. Deficits in form-from-motion perception.

We investigated form-from-motion perception (FFM perception) in a sample of 39 patients with acquired brain damage. Pronounced FFM deficits were found in two patients (FM1 and FM2) with biparietal lesions. Both patients were able to identify the relevant figure, when it was not embedded in obstructive texture. Moreover, they could localize the figures in the FFM condition, although they could not reliably identify them. The two patients had normal motion coherence thresholds. Their performance in a static figure-ground task did not differ from that of other patients. These findings imply that the FFM deficits are not caused by impairment of basic visual motion or form perception but are the consequence of damage to a parietal brain structure involved in the combined analysis of visual motion and form information. The nature and functional role of this brain structure as well as the implications of our results for models of FFM perception are discussed.

Adult↗
PubMed1996

Undersampling produces non-veridical motion perception, but not necessarily motion reversal, in peripheral vision.

We investigated motion perception in peripheral vision (10-40 deg eccentricity) for drifting gratings above and below the Nyquist limit set by neural sampling of the retinal image. We found that psychometric functions for motion discrimination rarely exhibited worse-than-chance performance indicative of motion reversal. A series of control experiments indicated that failure to demonstrate motion reversal could not be attributed to: (1) failure to detect the contrast of the stimulus; (2) failure to detect the motion of the stimulus; (3) use of an inappropriate range of spatial frequencies. Although consistent motion reversal was not observed, additional experiments demonstrated that motion perception was nevertheless non-veridical for spatial frequencies above the Nyquist limit. These seemingly contradictory results were reconciled by the observation that aliased patterns could appear to move in several different directions, all of which were different from the direction of stimulus, but only of which was opposite to the stimulus direction. Nyquist limits inferred from motion discrimination lie near the predictions for P-ganglion cells in human retina and well above M-cell predictions, which implies the M-cell array is too sparse to account for the limits to verdical motion perception in peripheral vision.

Contrast Sensitivity↗
PubMed1994

Modelling human motion perception. II. Beyond Fourier motion stimuli.

In the first part of this review a basic mechanism of motion perception was illustrated. The elementary motion detector (EMD) of the correlation type can account for the detection of "Fourier" motion stimuli in which the spatial intensity distribution on the retina is shifted over time. In recent years, novel classes of stimuli such as "drift-balanced" or "theta" motion (in which the picture elements carrying luminance contrast do not move, or move in the opposite direction to the traveling object defined by such element motion) were introduced into psychophysics. Such stimuli may play an important role in the understanding of "higher" visual processing which goes beyond the pure detection of motion. Thus, in the second part of the review, the question will be addressed as to what further processing steps, or more sophisticated mechanisms than the EMD, have to be assumed in order to understand more complex aspects of human motion perception.

Fourier Analysis↗
PubMed2002

Topography of evoked potentials associated with illusory motion perception as a motion aftereffect.

Motion aftereffect (MAE) is a type of motion illusion. After visual focusing on an object moving in one direction, an illusory perception of motion in the opposite direction occurs while the object suddenly stops moving. In this study we explored components and distribution of evoked potentials related to this motion illusion using MAE caused by motion of concentric rings. When a single array of moving rings was placed to straddle right and left visual fields, a significant bilateral increase of a positive component at about 160 ms (P160) was observed in the occipitotemporal region at the time subjects perceived the motion illusion; this increase was most prominent in the right posterior temporal region. Thus, an early positive component P160 occurs in relation to motion illusion, in agreement with previous results concerning perception of actual motion. When stimuli were presented to produce MAE limited to either the right or left visual hemifield, we also observed a P160 distributed mainly in the right temporal and parietal region. A significant increase in this component was observed in the right posterior temporal region with left hemifield stimulation, while no significant increase was observed with right hemifield stimulation. The right hemispheric dominance of P160 seemed to result partly from functional specialization of the right hemisphere, but hemispheric differences in attentional mechanisms also might contribute to the asymmetric distribution of P160.

Adult↗
PubMed1985

A revised analysis of the role of efference in motion perception.

The analysis of motion perception historically has included efferent as well as afferent mechanisms to account for the perception of motion during eye movement. The application of efferent mechanisms to motion perception has been limited, however, by several illusions which are apparently inconsistent with the notion that oculomotor mechanisms contribute to motion perception. An alternative account is presented of the manner in which efference may contribute to the perception of motion. It is proposed that distinct smooth eye-movement systems contribute differentially to object motion perception. Specifically, activity in the smooth pursuit system gives rise to the perception of object motion, whereas activity in the smooth component of reflexive eye movements does not. Tracking of a moving object results in object motion perception as a result of efference in the pursuit system. However, the pursuit system may be activated to oppose the smooth component of reflexive eye movements in order to preserve fixation on a stationary object. In such cases neither the fixated object nor the eye is moving but illusory movement results from the efference in the pursuit system. A number of illusory movement phenomena are interpreted in terms of this model.

Eye Movements↗
PubMed2003

Laterality and pattern persistence in bistable motion perception.

Bistable motion perception refers to two competing perceptions that can result when frames consisting of three elements are displaced laterally by one element. At short inter-frame intervals, the dominant percept is that the end elements in the display are moving; at long inter-frame intervals, perception is of all the elements moving coherently to the right or left. This research shows that coherent motion is more likely to be perceived when presentations are parafoveal than foveal and when they are to the right visual field than the left visual field. These results support the idea that visual pattern persistence is shorter in the parafovea than in the fovea, and shorter in the right than in the left visual field.

Adult↗
PubMed1991

Residual motion perception in a "motion-blind" patient, assessed with limited-lifetime random dot stimuli.

A neurological patient (L.M.) suffering a specific loss of visual motion perception (Zihl et al., 1983) due to extrastriate cortical damage was studied using random dot "limited-lifetime" stimuli with a direction discrimination task. With a stimulus like that of Newsome and Pare (1988), the patient exhibited a severe deficit for motion perception, only being able to perform well for very high values of coherence. Different versions of the stimulus were employed to separate out the effects of limited lifetime versus the effects of additive noise as coherence was lowered. When all "signal" dots had a fixed, specified value of lifetime, and varying percentages of "noise" dots were added, the patient showed a profound deficit. In contrast, a stimulus consisting of no noise dots at all, and signal dots having fixed values of lifetime, revealed relatively good performance for surprisingly brief dot lifetimes. Thus, it is the presence of noisy, incoherent dot motion, rather than brief lifetimes, that causes such poor performance on the stimulus of Newsome and Pare (1988). Most surprising was the finding that the presence of even very small percentages of stationary noise dots was sufficient to disrupt totally direction discrimination of moving signal dots. The findings reported here suggest that one major role of extrastriate cortical processing might be the interpretation of stimuli that suffer from an impaired signal-to-noise ratio; the most commonly encountered form of "noise" would presumably be contamination by irrelevant directional spatio-temporal frequency components.

Humans↗
PubMedDate not supplied

Motion perception following lesions of the superior temporal sulcus in the monkey.

We examined the effect of bilateral ibotenic acid lesions, aimed at areas MT/MST in three macaques, on their perception of motion. The medial boundary of the lesions in the three monkeys was near the dorsal end of the STS, but the lesions extended different lengths ventrally along the STS. The lesions extended the shortest distance ventrally monkeys 1 and 2, covering most of MST but possibly sparing a portion of lateral MT. That in monkey 3 damaged all of MT and MST bilaterally and extended through most of FST. All three lesions caused a temporary disruption, followed by at least partial recovery, of most motion thresholds. Permanent effects of the lesions on visual sensitivity were graded with lesion extent. Contrast sensitivity for detecting low-spatial-frequency (1 cycle/degree) drifting gratings over a wide range of drift rates, as well as for identifying their direction of motion, was slightly affected only in monkey 3. Only monkeys 2 and 3 showed a deficit in discriminating stimulus speed, and the size of the loss was two- to fourfold. Discrimination of opposite directions of dot pattern motion, which required integration of local motion signals, was mildly affected in monkeys 2 and 3, and not affected in monkey 1. However, addition of directional noise to this discrimination caused the performance of all monkeys to be permanently disrupted, especially that of monkeys 2 and 3. Finally, direction difference thresholds were elevated by a factor of 2-4 after the lesions in all three monkeys. Many of these deficits were more pronounced during the first 2 months of testing following the lesion. Thus, our results demonstrate that areas within dorsal STS make an important contribution to the performance of various motion perception tasks including the discrimination of small differences in direction and speed, and the perception of global motion in the presence of directional noise. The residual motion perception, even in the monkey with virtually complete removal of areas MT/MST, may suggest either that these tasks are normally mediated in part by cortical areas outside of areas MT and MST, or that the disrupted functions were partially assumed by other cortical areas after lesions.

Animals↗
PubMed1993

Quantification of monocular optokinetic nystagmus asymmetries and motion perception with motion-nulling techniques.

When tested monocularly, strabismic and amblyopic subjects often show asymmetries of optokinetic nystagmus (OKN), with OKN being more readily elicited by temporal-to-nasal than by nasal-to-temporal stimulus motion. We tested five visually normal subjects and ten strabismic and/or amblyopic subjects by use of motion-nulling stimuli, which consisted of superimposed temporal-to-nasal and nasal-to-temporal sinusoidal-grating components with a summed contrast of 100%. Both the direction of OKN and the subject's perceived direction of motion (PDM) were tested. Most normal subjects showed symmetrical OKN and PDM, but a rightward OKN bias was observed in one of the visually normal subjects. Temporal-to-nasal eye-movement biases were seen in most strabismic and amblyopic subjects, whereas PDM biases were smaller and less frequent. The primary purpose of this study was to demonstrate the feasibility of quantifying OKN and PDM asymmetries in a diverse group of visually abnormal adults by use of the motion-nulling technique. Application of this technique to larger and more homogeneous clinical populations may contribute to the continued differentiation and characterization of variants of the visual disorders associated with strabismus and amblyopia and with other defects of binocular vision.

Adolescent↗