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Results for “Motion Perception”

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At least 253 records · Page 14Linked to original sources
PubMed2006

Frame of reference transformations in motion perception during smooth pursuit eye movements.

Smooth pursuit eye movements change the retinal image velocity of objects in the visual field. In order to change from a retinocentric frame of reference into a head-centric one, the visual system has to take the eye movements into account. Studies on motion perception during smooth pursuit eye movements have measured either perceived speed or perceived direction during smooth pursuit to investigate this frame of reference transformation, but never both at the same time. We devised a new velocity matching task, in which participants matched both perceived speed and direction during fixation to that during pursuit. In Experiment 1, the velocity matches were determined for a range of stimulus directions, with the head-centric stimulus speed kept constant. In Experiment 2, the retinal stimulus speed was kept approximately constant, with the same range of stimulus directions. In both experiments, the velocity matches for all directions were shifted against the pursuit direction, suggesting an incomplete transformation of the frame of reference. The degree of compensation was approximately constant across stimulus direction. We fitted the classical linear model, the model of Turano and Massof (2001) and that of Freeman (2001) to the velocity matches. The model of Turano and Massof fitted the velocity matches best, but the differences between de model fits were quite small. Evaluation of the models and comparison to a few alternatives suggests that further specification of the potential effect of retinal image characteristics on the eye movement signal is needed.

Adult↗
PubMedDate not supplied

Arthrokinetic information affects linear self-motion perception.

A sensation of linear self-motion can be induced in a blindfolded stationary sitting subject, who keeps contact with a linearly moving platform (acceleration 0.1 m/s2) in the frontoparallel plane by means of a hand-over-hand walking action. When discordant suprathreshold vestibular information from the otoliths is added by moving the subject laterally (acceleration 0.1 m/s2) in the same direction as the platform (acceleration of the platform 0.2 m/s2, so the arthrokinetic stimulus is also an acceleration of 0.1 m/s2, but into the opposite direction), the arthrokinetic information was found to have a predominant effect on the perceived direction of self-motion.

Humans↗
PubMed1994

An electrophysiological correlate of learning in motion perception.

We investigated learning in a motion-detection task using both psychophysical and neurophysiological methods in normal humans. A total of 20 naive observers had to discriminate between a small motion to the left versus to the right (jump displacement) or between a motion upward versus downward. Their performance improved significantly within less than 30 min in discriminating between directions in the psychophysical jump-displacement task. The improvement of performance with practice was very specific and did not transfer to the same stimulus rotated by 90 degrees. After training for the same task, multichannel evoked-potential recordings changed significantly in component latency and in the distribution of field potentials. This indicates that neuronal ensembles rather than single cells are involved in perceptual learning. Significant differences between the potential distributions occur for potentials at latencies of less than 100 ms over the occipital pole, suggesting an involvement of and plasticity in the primary visual cortex of human adults.

Adult↗
PubMed1991

Visual motion perception from stimulation of the human medial parieto-occipital cortex.

Visual phenomena evoked by direct electrical stimulation of extrastriate cortex were observed in 30 epileptic patients as part of a presurgical investigation. An incremental sequence of low-level bipolar stimulation trains was delivered at medial and lateral pairs of contacts of stereotaxically-implanted multilead intracerebral electrodes in parietal, occipital and posterior temporal regions. Diffusion of stimulus afterdischarges was monitored by electrodes in temporal and frontal lobes and by the non-stimulated contacts of the stimulated electrode. Localized stimulations evoked few visual phenomena. The strongest anatomo-perceptual correlation was found for stimulation in the medial parieto-occipital fissure which evoked visual motion phenomena in all three patients stimulated in that region. The evoked motion perceptions were not associated with eye movements or any particular localization of the epileptic focus. These perceptions were only evoked once outside of the medial PO region at the 61 sites examined. The results suggest that the medial parieto-occipital region is closely linked to the human visual motion processing system.

Brain Mapping↗
PubMed1997

A belongingness principle of motion perception.

Four experiments are reported that investigated the role of the perceived coplanarity of a moving target with respect to a frame of reference in the third dimension on the perceived path of that target. When a target dot and small moving frame appeared coplanar, the dot's perceived trajectory was governed entirely by its changing position relative to the moving frame. However, when the target and a large stationary frame appeared in a different plane than the small moving frame, the motion of the dot was seen independently of the moving frame. The results support a belongingness principle of motion perception: The displacement of an object relative to a frame of reference to which it belongs governs its perceived path of motion.

Adult↗
PubMed1993

Representational development of direction in motion perception: a fragile process.

Response to a change in direction is more rapid if the target moves in a predictable direction before the change than if the pre-change direction is not predictable. However, if the target trajectory is viewed for approximately half a second before the change in direction, the effect of directional predictability disappears. Visual information gathered prior to change in direction is used to construct an increasingly more accurate representation of target trajectory. To study this process, we inject various temporal transients into the trajectory prior to the change in direction. We find that extraction of directional information is interrupted if: (i) motion continues along a constant trajectory, but the target disappears briefly behind an implicit or real occluder, (ii) the target pauses briefly, but remains visible, or (iii) the target changes speed briefly, while continuing to move in the same direction. The theoretical implications for motion perception are discussed. These implications include a framework for understanding interactions between stimulus-derived information and a priori information.

Cognition↗
PubMed1993

The effect of interactions between one-dimensional component gratings on two-dimensional motion perception.

Ferrera and Wilson [(1990) Vision Research, 30, 273-287] reported veridical perception of the direction of motion of Type I plaids, whose component gratings span the resultant direction, but marked misperception of the direction of motion of Type II plaids, whose component gratings both lie on one side of the resultant direction. Because they failed to find any effect of component direction (angular) separation on this misperception, Ferrera and Wilson concluded that the misperception was not due to perceptual repulsion of component directions. We report that component direction repulsion does occur, that plaid direction misperception is tuned to component separation, with larger repulsions for smaller angles. It is concluded that there is no fundamental difference in direction coding for Type I and Type II plaids, and that Ferrera and Wilson failed to find a direction separation effect because the range of separations they used was insufficiently broad to detect the slope of the angular function.

Humans↗
PubMed2005

Contribution of self-motion perception to acoustic target localization.

CONCLUSION: The findings of this study suggest that acoustic spatial perception during head movement is achieved by the vestibular system, which is responsible for the correct dynamic of acoustic target pursuit. OBJECTIVE: The ability to localize sounds in space during whole-body rotation relies on the auditory localization system, which recognizes the position of sound in a head-related frame, and on the sensory systems, namely the vestibular system, which perceive head and body movement. The aim of this study was to analyse the contribution of head motion cues to the spatial representation of acoustic targets in humans. MATERIAL AND METHODS: Healthy subjects standing on a rotating platform in the dark were asked to pursue with a laser pointer an acoustic target which was horizontally rotated while the body was kept stationary or maintained stationary while the whole body was rotated. The contribution of head motion to the spatial acoustic representation could be inferred by comparing the gains and phases of the pursuit in the two experimental conditions when the frequency was varied. RESULTS: During acoustic target rotation there was a reduction in the gain and an increase in the phase lag, while during whole-body rotations the gain tended to increase and the phase remained constant. The different contributions of the vestibular and acoustic systems were confirmed by analysing the acoustic pursuit during asymmetric body rotation. In this particular condition, in which self-motion perception gradually diminished, an increasing delay in target pursuit was observed.

Acoustics↗
PubMed1995

Does motion perception follow Weber's law?

The subjective strength of a percept often depends on the stimulus intensity in a nonlinear way. Such coding is often reflected by the observation that the just-noticeable difference between two stimulus intensities (JND) is proportional to the absolute stimulus intensity. This behaviour, which is usually referred to as Weber's Law, can be interpreted as a compressive nonlinearity extending the operating range of a sensory system. When the noise superimposed on a motion stimulus is increased along a logarithmic scale (in order to provide linear steps in subjective difference) in motion-coherency measurements, observers often report that the subjective differences between the various noise levels increase together with the absolute level. This observation could indicate a deviation from Weber's Law for variation of motion strength as obtained by changing the signal-to-noise ratio in random-dot kinematograms. Thus JNDs were measured for the superposition of uncorrelated random-dot patterns on static random-dot patterns and three types of motion stimuli realised as random-dot kinematograms, namely large-field and object 'Fourier' motion (all or a group of dots move coherently), 'drift-balanced' motion (a travelling region of static dots), and paradoxical 'theta' motion (the dots on the surface of an object move in opposite direction to the object itself). For all classes of stimuli, the JNDs when expressed as differences in signal-to-noise ratio turned out to increase with the signal-to-noise ratio, whereas the JNDs given as percentage of superimposed noise appear to be similar for all tested noise levels. Thus motion perception is in accordance with Weber's Law when the signal-to-noise ratio is regarded as stimulus intensity, which in turn appears to be coded in a nonlinear fashion. In general the Weber fractions are very large, indicating a poor differential sensitivity in signal-to-noise measurements.

Acceleration↗
PubMed2005

An event-related potentials study of biological motion perception in human infants.

To clarify the dynamical processing aspect of biological motion (BM) perception from a developmental point of view, we measured event-related potentials (ERPs) in 8-month-old infants during the perception of BM or a scrambled motion (SM; randomization of BM's spatial structure). We found that activation of the right hemisphere in 8-month-old infants was similar to that of adults, suggesting that the neural substrates for processing BM perception begin to mature at around 8 months of age.

Analysis of Variance↗
PubMed1998

Alteration of eye movements and motion perception in microgravity.

This review article summarizes the results of space research on eye movements and subjective perception during vestibular stimulation. Inflight and postflight changes in reflex eye movements gain are described for head angular rotation (yaw, pitch, and roll), linear acceleration, off-vertical axis rotation, and optokinetic stimulation. There is evidence that changes in eye movements in microgravity primarily occur for head movements in pitch or roll which normally stimulate the otolith organs on Earth, but the data are not conclusive. The relationship between the eye movements gain and self-motion perception remains to be determined. We advocate the use of a human on- and off-axis rotator combined with the measurements of both tri-dimensional eye movement and perceptual response as a method to systematically investigate the adaptive changes in vestibular function to microgravity.

Eye Movements↗
PubMed2002

Implicit motion perception in schizotypy and schizophrenia: a Representational Momentum study.

INTRODUCTION: Human observers exhibit a distortion in recognition memory for pictures that imply motion because of an automatic mental process, which extrapolates along the implied trajectory of the picture. This is known as Representational Momentum (RM). Converging evidence (functional imaging; magnetic stimulation studies) suggests activity in area MT/MST (V5) is necessary for RM to occur. Patients with schizophrenia and healthy schizotypic individuals have been found to show motion perception deficits and abnormal eye-tracking (both indicative of abnormal functioning within brain area V5), therefore it was hypothesised that these individuals would show a reduced or absent RM effect. METHOD: Fifty healthy individuals and seven patients diagnosed with schizophrenia undertook a task previously found to elicit the RM effect. RESULTS: Although the size of the RM effect was not significantly different between either low and high schizotypes or low schizotypes and patients, there was a trend (in the opposite direction to that predicted) for the patients with schizophrenia and the high schizotypes to exhibit a larger RM effect. CONCLUSION: The findings are discussed in terms of functional connectivity between frontal areas and V5, and of schizophrenia involving a failure to inhibit automatic processes.

Journal Article↗
PubMed2005

What learning to see arbitrary motion tells us about biological motion perception.

In separate studies, observers viewed upright biological motion, inverted biological motion, or arbitrary motion created from systematically randomizing the positions of point-light dots. Results showed that observers (a) could learn to detect the presence of arbitrary motion, (b) could not learn to discriminate the coherence of arbitrary motion, although they could do so for upright biological motion, (c) could apply a detection strategy to learn to detect the presence of inverted biological motion nearly as well as they detected upright biological motion, and (d) performed better discriminating the coherence of upright biological motion compared with inverted biological motion. These results suggest that learning and form information play an important role in perceiving biological motion, although this role may only be apparent in tasks that require processing information from multiple parts of the motion display.

Attention↗
PubMed2002

Neural correlates of structure-from-motion perception in macaque V1 and MT.

Structure-from-motion (SFM) is the perception of three-dimensional shape from motion cues. We used a bistable SFM stimulus, which can be perceived in one of two different ways, to study how neural activity in cortical areas V1 and MT is related to SFM perception. Monkeys performed a depth-order task, where they indicated in which direction the front surface of a rotating SFM cylinder display was moving. To prevent contamination of the neural data because of eye position effects, all experiments with significant effects of radius, vergence, and velocity were excluded. As expected, the activity of approximately 50% of neurons in V1 and approximately 80% of neurons in MT is affected by the stimulus. Furthermore, the activity of 20% of neurons in area V1 is modulated with the percept. This proportion is higher in MT, where the activity of >60% of neurons is modulated with the percept. In both areas, this perceptual modulation occurs only in neurons with activity that is also affected by the stimulus. The perceptual modulation is not correlated with neural tuning properties in area V1, but it is in area MT. Together, these results suggest that V1 is not directly involved in the generation of the SFM percept, whereas MT is. The perceptual modulation in V1 may be attributable to top-down feedback from MT.

Action Potentials↗
PubMed1985

Eccentricity-dependent scaling of the limits for short-range apparent motion perception.

The ability to report the direction of apparent motion when an array of random dots is displaced fails when the displacement exceeds a limiting value (dmax). We find that dmax increases rapidly with retinal eccentricity, in a manner different from spatial measures such as acuity which are believed to depend on the "magnification factor" of projection to area 17. The minimum displacement giving detectable motion (dmin) shows a shallower increase with eccentricity which is more compatible with the variation of cortical magnification. The dependence of apparent motion on the timing variables (exposure duration, inter-stimulus interval) changes negligibly with eccentricity. Consequently the dynamic range and the upper limit of detectable velocities increases greatly with eccentricity. The increase of dmax with eccentricity means that the perception of apparent motion will show an approximate invariance with display scale, even though dmax has a locally fixed value depending on receptive field structure.

Fixation, Ocular↗
PubMed2006

Visual motion interferes with tactile motion perception.

Previous studies have demonstrated that visual apparent motion can alter the judgment of auditory apparent motion. We investigated the effect of visual apparent motion on judgments of the direction of tactile apparent motion. When visual motion was presented at the same time as, but in a direction opposite to, tactile motion, accuracy in judging the direction of tactile apparent motion was substantially reduced. This reduction in performance is referred to as 'the congruency effect'. Similar effects were observed when the visual display was placed either near to the tactile display or at some distance from the tactile display (experiment 1). In experiment 2, the relative alignment between the visual and tactile directions of motion was varied. The size of the congruency effect was similar at 0 degrees and 45 degrees alignments but much reduced at a 90 degrees alignment. In experiment 3, subjects made confidence ratings of their judgments of the direction of the tactile motion. The results indicated that the congruency effect was not due to subjects being unsure of the direction of motion and being forced to guess. In experiment 4, static visual stimuli were shown to have no effect on the judgments of direction of the tactile stimuli. The extent to which the congruency effect reflects capture effects and is the result of perceptual versus post-perceptual processes is discussed.

Analysis of Variance↗
PubMed2005

A binocular rivalry study of motion perception in the human brain.

The relationship between brain activity and conscious visual experience is central to our understanding of the neural mechanisms underlying perception. Binocular rivalry, where monocular stimuli compete for perceptual dominance, has been previously used to dissociate the constant stimulus from the varying percept. We report here fMRI results from humans experiencing binocular rivalry under a dichoptic stimulation paradigm that consisted of two drifting random dot patterns with different motion coherence. Each pattern had also a different color, which both enhanced rivalry and was used for reporting which of the two patterns was visible at each time. As the perception of the subjects alternated between coherent motion and motion noise, we examined the effect that these alternations had on the strength of the MR signal throughout the brain. Our results demonstrate that motion perception is able to modulate the activity of several of the visual areas which are known to be involved in motion processing. More specifically, in addition to area V5 which showed the strongest modulation, a higher activity during the perception of motion than during the perception of noise was also clearly observed in areas V3A and LOC, and less so in area V3. In previous studies, these areas had been selectively activated by motion stimuli but whether their activity reflects motion perception or not remained unclear; here we show that they are involved in motion perception as well. The present findings therefore suggest a lack of a clear distinction between 'processing' versus 'perceptual' areas in the brain, but rather that the areas involved in the processing of a specific visual attribute are also part of the neuronal network that is collectively responsible for its perceptual representation.

Adult↗