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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↗
PubMed2006

Auditory motion perception activates visual motion areas in early blind subjects.

We have previously shown that some visual motion areas can be specifically recruited by auditory motion processing in blindfolded sighted subjects [Poirier, C., Collignon, O., De Volder, A.G., Renier, L., Vanlierde, A., Tranduy, D., Scheiber, C., 2005. Specific activation of V5 brain area by auditory motion processing: an fMRI study. Brain Res. Cogn. Brain Res. 25, 650-658]. The present fMRI study investigated whether auditory motion processing may recruit the same brain areas in early blind subjects. The task consisted of simultaneously determining both the nature of a sound stimulus (pure tone or complex sound) and the presence or absence of its movement. When a movement was present, blind subjects had to identify its direction. Auditory motion processing, as compared to static sound processing, activated the brain network of auditory and visual motion processing classically observed in sighted subjects. Accordingly, brain areas previously considered as specific to visual motion processing could be specifically recruited in blind people by motion stimuli presented through the auditory modality. This indicates that the occipital cortex of blind people could be organized in a modular way, as in sighted people. The similarity of these results with those we previously observed in sighted subjects suggests that occipital recruitment in blind people could be mediated by the same anatomical connections as in sighted subjects.

Adolescent↗
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↗
PubMed2006

A single motion system suffices for global-motion perception.

Global-motion perception is the perception of coherent motion in a noisy motion stimulus. Thresholds for coherent motion perception were measured for different combinations of signal and noise speeds. Previous research [Edwards, M., Badcock, D. R., & Smith, A. T. (1998). Independent speed-tuned global-motion systems. Vision Research, 38 (11), 1573-1580; Khuu, S. K., & Badcock, D. R. (2002). Global speed processing: evidence for local averaging within, but not across two speed ranges. Vision Research, 42 (28), 3031-3042.] showed that thresholds were elevated when signal and noise speeds were similar, but not when they were different. The regions of increased threshold values for low and high signal speeds showed little overlap. On the basis of this evidence two independent speed-tuned systems were proposed: one for slow and one for fast-motion. However, in those studies only two signal speeds were used. We expanded the results by measuring threshold-curves for four different signal speeds. Considerable overlap of the threshold-curves was found between conditions. These results speak against a bipartite global-motion system. Model simulations indicate that present and previous experimental results can be produced by a single motion system providing that the mechanisms within it are speed-tuned.

Humans↗
PubMed2005

Vertical linear self-motion perception during visual and inertial motion: more than weighted summation of sensory inputs.

We evaluated visual and vestibular contributions to vertical self motion perception by exposing subjects to various combinations of 0.2 Hz vertical linear oscillation and visual scene motion. The visual stimuli presented via a head-mounted display consisted of video recordings of the test chamber from the perspective of the subject seated in the oscillator. In the dark, subjects accurately reported the amplitude of vertical linear oscillation with only a slight tendency to underestimate it. In the absence of inertial motion, even low amplitude oscillatory visual motion induced the perception of vertical self-oscillation. When visual and vestibular stimulation were combined, self-motion perception persisted in the presence of large visual-vestibular discordances. A dynamic visual input with magnitude discrepancies tended to dominate the resulting apparent self-motion, but vestibular effects were also evident. With visual and vestibular stimulation either spatially or temporally out-of-phase with one another, the input that dominated depended on their amplitudes. High amplitude visual scene motion was almost completely dominant for the levels tested. These findings are inconsistent with self-motion perception being determined by simple weighted summation of visual and vestibular inputs and constitute evidence against sensory conflict models. They indicate that when the presented visual scene is an accurate representation of the physical test environment, it dominates over vestibular inputs in determining apparent spatial position relative to external space.

Adolescent↗
PubMed1984

Coherent global motion percepts from stochastic local motions.

A percept of global, coherent motion results when many different localized motion vectors are combined. We studied the percept with dynamic random dot kinematograms whose elements took independent, random walks of constant step size; their directions of displacement were drawn from a uniform distribution. The tendency to see global, coherent flow along the mean of the uniform distribution varied with the range of the distribution. Psychometric functions were obtained with kinematograms having various step sizes and element densities. The changes in the psychometric function with step size and density are consistent with Ullman's "minimal map theory" of motion correspondence.

Form Perception↗
PubMed1994

Transparent motion perception as detection of unbalanced motion signals. III. Modeling.

In the preceding two companion articles we studied the conditions under which transparent motion perception occurs through psychophysical experiments, and investigated the underlining neural mechanisms through physiological recordings. The main finding of our perceptual experiments was that whenever a display has finely balanced motion signals in all local areas, it is perceptually nontransparent, and that transparent displays always contain motion signals in different directions that are either spatially unbalanced, or unbalanced in their disparity or spatial frequency contents. In the physiological experiments, we found two stages in the processing of transparent stimuli. The first stage is located primarily in area V1. At this stage motion measurements are made and V1 cells respond well to both the balanced, nontransparent stimuli and the unbalanced, perceptually transparent stimuli. The second stage is located primarily in area MT. MT cells show strong suppression between opposite directions of motion. The suppression for the unbalanced, transparent stimuli is significantly less than that for the balanced, nontransparent stimuli. Therefore, the activity in the second, MT stage correlates better with the perception of motion transparency than the first, V1 stage, which does not distinguish reliably between transparent and nontransparent motion. The above experiments suggest a two-stage model of motion perception with a motion measurement stage in V1 and an opponent-direction suppression stage in area MT. In this article we explicitly test this model through analysis and computer simulations, and compare the response of the model to the perceptual and physiological results using the same balanced and unbalanced stimuli we used in the experiments. In the first stage of the computational model, motion energies in different spatial frequency and disparity ranges are extracted from each local region. Similar to V1, this stage does not distinguish between the balanced and unbalanced stimuli. In the subsequent stage motion energies of opposite directions but with same spatial frequency and disparity contents suppress each other using subtractive or divisive inhibition. This stage responds significantly better to the transparent stimuli than to the nontransparent ones, in agreement with MT activity.

Animals↗
PubMed1990

The temporal range of motion sensing and motion perception.

Apparent motion (AM) was studied using the missing-fundamental square-wave grating, displaced discretely over time. At inter-stimulus intervals (ISIs) greater than about 40 msec, AM was seen in the direction of displacement of the visible features of the pattern, while at shorter ISIs AM was seen in the reversed direction, following the displacement of the third harmonic spatial frequency component. This confirms (a) that the "long-range", feature-based process can bridge much greater time-gaps than the "short-range" motion sensors and (b) that the missing-fundamental pattern is a particularly useful tool for teasing the two processes apart.

Humans↗
PubMed1997

Visual extinction and prior entry: impaired perception of temporal order with intact motion perception after unilateral parietal damage.

Two patients with left-sided visual extinction after right parietal damage were each given two 'prior entry' tasks that have recently been used to study attentional biases in normals. The first task presented two unconnected bars, one in each visual field, with the patients asked to judge which appeared sooner. Both patients reported that the right bar preceded the left unless the latter led by over 200 msec, suggesting a severe bias to the right affecting the time-course of visual awareness. The second task presented one continuous line in a scrolling format across the same spatial extent, with the patients asked to judge which direction the line moved in. The patients now performed normally. Thus, the perception of temporal order for separate events was impaired by the lesions, but without disrupting motion perception within single events. The implications are discussed for theories of normal and pathological attention, visual awareness, and motion perception.

Aged↗
PubMed2004

Effects of spatial arrangement of visual stimulus on inverted self-motion perception induced by the foreground motion: examination of OKN-suppression hypothesis.

Our previous study revealed that a slowly moving foreground, which is presented in front of a fast-moving orthogonal background, can induce self-motion perception in the same direction as its motion (inverted vection; Vis. Res. 40 (2000) 2915). The present study shows that inverted vection becomes stronger in the conditions where the foreground stimulus is presented in the central area of observer's visual field and the observer's eyes converge on the same depth plane. These stimulus conditions are consistent with the one where the foreground can induce observer's optokinetic nystagmus more effectively, and therefore, the results of this study support our hypothesis in that mis-registered eye-movement information caused by the suppression of optokinetic nystagmus induced by the foreground motion is a critical factor in perceiving inverted vection.

Adult↗
PubMed1994

Modeling human motion perception. I. Classical stimuli.

Motion perception is one of the most prominent tasks of the visual system and therefore has been extensively investigated both experimentally and theoretically. A classical model describing the mechanism of motion detection originally developed in the context of insect orientation behavior, the elementary motion detector (EMD) of the correlation type, turned out to be very powerful in explaining many basic aspects of human motion perception. For more complex visual tasks, like the discrimination of a figure from its background by relative motion, on the other hand, further processing of motion information is required. In the first part of this review it will be illustrated by means of a few examples, what kind of motion information can be derived from the mere correlation-type model, and what perceptual phenomena can be accounted for by the EMD. In the second part, more recently developed stimuli will be introduced to answer the question what further processing steps, or more sophisticated mechanisms than the EMD, have to be assumed in order to understand "higher" aspects of human motion perception.

Cybernetics↗
PubMed1990

Motion perception is abnormal in primary open-angle glaucoma and ocular hypertension.

Several lines of evidence suggest that the large optic nerve fibers, which form the magnocellular retinocortical pathway, are preferentially susceptible to early glaucomatous damage. It is evident from studies of the functional architecture of the visual system that the magnocellular pathway underlies the global perception of motion. Therefore, we have developed a psychophysical technique for assessing motion detection thresholds in patients with ocular hypertension (OHT) and primary open-angle glaucoma (POAG). For this purpose we employed a dynamic random dot display that contained varying degrees of a coherent motion signal embedded within a background of random motion noise. We used this technique to measure motion thresholds in POAG patients (n = 37), OHT patients (n = 14), and age-matched controls (n = 39). Motion thresholds were elevated by 70% for the POAG group and 44% for the OHT group relative to controls. In the same patients, no significant deficit in form discrimination was found as measured by Pelli-Robson charts. Our results demonstrate that significant motion perception deficits are evident in POAG and OHT. These findings support the suggestion that significant and selective damage to the magnocellular pathway occurs in OHT and POAG and indicate that motion threshold testing may reveal preclinical optic nerve disease in early POAG.

Contrast Sensitivity↗
PubMed1994

Transparent motion perception as detection of unbalanced motion signals. I. Psychophysics.

Our visual system can solve the difficult problem of representing multiple motions in the same part of the visual space, the motion transparency problem. We investigated the conditions under which transparent motion perception occurs through psychophysical observations, using a series of visual displays composed of two simple patterns moving in opposite directions. We found that whenever a display has finely balanced opposing motion signals in all local regions, it is perceptually nontransparent. The displays that appeared transparent always contain locally unbalanced motion signals, with some local regions having net motion signals in one direction and some other regions in the opposite direction. These interdigitating net motion signals in both directions appear to be integrated separately to form two overlapping transparent surfaces. Displays that were spatially balanced could be made perceptually transparent if the two components moving in opposite directions were at different stereo depth planes or had different spatial frequency contents. Our results can be explained by proposing a disparity- and spatial frequency-specific suppression stage in the motion pathway, at which motion signals of different directions, but of the same disparity and spatial frequency contents, locally inhibit each other. Such a mechanism would suppress noise input to the motion system, which generally activates several direction channels simultaneously, and would still not eliminate activity evoked by transparent surfaces that are at different depths or have different textures.

Cues↗
PubMed2002

Spatial and temporal characteristics of visual motion perception involving V5 visual cortex.

The anatomical substrates of the perception of motion have not yet been established in a detailed way on an individual level. The aim of this study was to develop a systematic procedure for mapping the visual cortex using Transcranial Magnetic Stimulation (TMS). The results showed that such an individual and detailed map of the spatial and temporal characteristics of motion perception can be constructed using TMS.

Adult↗
PubMed2006

The influence of biological motion perception on structure-from-motion interpretations at different speeds.

Nonrigid point-light representations of biological motion are ideal to test higher level influences on structure-from-motion (SFM) perception. Here, we investigated the influence of biological motion perception on 3D SFM interpretations at different speeds. We presented nonrigid biological motion and rigid structures rotating around the vertical axis. The familiarity of the stimuli was changed by presenting three walker types: normal, inverted, and phase scrambled. Subjects had to discriminate rotation in depth and rigidity. We found that at lower-than-natural gait speeds, subjects perceived nonrigid biological motion to be rotating in depth, especially when the walker type was less familiar. In contrast, the percept of rigidity was correct at all speeds. A second experiment, in which a constant fraction of the gait cycle was presented, confirmed the influence of speed and additionally showed that brief displays of a familiar form at a high speed facilitate biological motion interpretations. The more veridical percept of rotation toward higher speeds fits the idea of biological motion channels tuned to higher-more natural walking-speeds that overrule a default assumption to perceive trajectories in depth. We also speculate that the rotation-in-depth percept at lower speeds points toward the existence of low-speed-tuned object motion channels.

Depth Perception↗
PubMed1992

ON- and OFF-pathways form separate neural substrates for motion perception: psychophysical evidence.

We have tested the hypothesis that in humans the signals carried by ON- and OFF-pathway respectively are processed for the perception of motion by two distinct physiological substrates. In vertebrates, onset of a bright visual stimulus is signaled to the CNS by ON-center retinal ganglion cells; onset of a dark stimulus is transmitted by OFF-center cells. We chose apparent motion generated by successive presentation of two adjacent lines as a stimulus. Lines presented on a bright background were either darker or brighter than this background. Delayed onset of a pair of bright or dark lines elicits apparent motion at the same time fulfilling the constraint of stimulating either ON- or OFF-center ganglion cells, respectively. We determined the threshold delay needed for subjects to perceive the temporal order of the onset of the two lines for various angular separations. The threshold delay for a pair of bright lines stayed low for separations from 2' to 7'. The threshold delay for a pair of dark lines was low only within a narrow range of separations centered around 3'. The variation of thresholds with line distance must reflect the existence of a limited processing zone for the perception of motion. The diameter of the processing zone for bright lines is about twice as large as that for dark lines. This suggests that in humans the separation of ON- and OFF-pathways extends to the early stages of motion perception. To test this hypothesis independently, thresholds were determined when a bright and a dark line were presented in succession. This was done for a separation of 3' where thresholds for a pair of lines with equal contrast are similarly low. Temporal order was perceived correctly only when the delay was at least two to four times as high as the threshold delays found for the equal contrast stimuli.

Humans↗
PubMed1994

Motion perception in optic neuropathy.

We tested motion perception in 15 eyes of 13 patients with optic neuropathy. Eleven of the eyes had optic neuritis. The motion perception paradigm tested subjects' ability to discriminate the direction of a global coherent motion signal amid varying levels of background noise. The results showed defective motion processing in eight of the 15 eyes. This defect was not due to low visibility (poor spatial resolution), since 11 of the 15 eyes had Snellen acuities of 20/20 or better. Neither was impaired motion perception due to decreased luminance sensitivity, since attenuating the display signal by 2.1 log units (0.6 units more than the worst relative afferent pupillary defect in any patient) in five normal eyes had no effect. Motion perception and critical flicker fusion were independent of each other. Given proposals that both depend exclusively on the same M, or transient, channel, we had not predicted this double dissociation between flicker and motion perception.

Adult↗