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PubMedDate not supplied

Topographical analysis of motion-triggered visual-evoked potentials in man.

PURPOSE: The middle temporal (MT) area of the cortex of the monkey is involved in visual motion analysis. Previous studies using brain-imaging techniques have shown that the area around the anterior occipital cortex in man is homologous to the area MT of the monkey. In this study, we investigated the cortical components of motion-triggered visual evoked potentials and their topography in the visual cortex of man. METHODS: Visual evoked potentials to the onset of a visual motion stimulus (m-VEPs) were recorded from 5 normal subjects aged 25 to 34 years. A random dot pattern was used as the stimulus for the m-VEPs. The dots moved horizontally to the right and then to the left alternately for 500 milliseconds with interstimulus intervals of 1500 milliseconds. The speed of motion was varied in five steps from 5-25 degrees/s. Fifteen electrodes were placed on the occiput around O(z) at 5-cm intervals. Color contour maps showing the distribution of voltage over the 15 electrodes at latencies ranging from 0-200 milliseconds with a 20-millisecond interval were made for each subject. These were coregistered with three-dimensional magnetic resonance images of the same brain to specify the topography of the main components of the m-VEPs in relation to the sulcal and gyral pattern of the visual cortex. RESULTS: We consistently observed a positive wave with a peak latency of about 100 milliseconds (P100) and a negative wave with a peak latency of about 150 milliseconds (N150) for all subjects. Topographical analysis showed that P100 was dominant in a relatively wide area caudal to O(z), whereas N150 was dominant in a relatively small area posterior to the right anterior occipital sulcus, which included the area corresponding to the area MT in man. CONCLUSIONS: These findings suggest that N150 represents the activity of the area MT in the human visual cortex related to motion perception.

Adult↗
PubMed2002

Should bad workmen always blame their tools?

In this issue of Neuron, differentiated brain regions in humans that are selectively responsive to viewing motion: (1) of humans, (2) of tools/utensils, and (3) in general. Active regions were the superior temporal sulcus, middle temporal gyrus, and MT/V5, respectively. This study provides impetus for future work in motion perception and its relationship to apraxia.

Animals↗
PubMed2006

Spatiotemporal tuning of rapid interactions between visual-motion analysis and reaching movement.

In addition to the goal-directed preplanned control, which strongly governs reaching movements, another type of control mechanism is suggested by recent findings that arm movements are rapidly entrained by surrounding visual motion. It remains, however, controversial whether this rapid manual response is generated in a goal-oriented manner similarly to preplanned control or is reflexively and directly induced by visual motion. To investigate the sensorimotor process underlying rapid manual responses induced by large-field visual motion, we examined the effects of contrast and spatiotemporal frequency of the visual-motion stimulus. The manual response amplitude increased steeply with image contrast up to 10% and leveled off thereafter. Regardless of the spatial frequency, the response amplitude increased almost proportionally to the logarithm of stimulus speed until the temporal frequency reached 15-20 Hz and then fell off. The maximum response was obtained at the lowest spatial frequency we examined (0.05 cycles/degrees). These stimulus specificities are surprisingly similar to those of the reflexive ocular-following response induced by visual motion, although there is no direct motor entrainment from the ocular to manual responses. In addition, the spatiotemporal tuning is clearly different from that of perceptual effects caused by visual motion. These comparisons suggest that the rapid manual response is generated by a reflexive sensorimotor mechanism. This mechanism shares a distinctive visual-motion processing stage with the reflexive control for other motor systems yet is distinct from visual-motion perception.

Adult↗
PubMed2006

Subthreshold features of visual objects: unseen but not unbound.

The object is a basic unit that is thought to organize the way in which we perceive and think about the world. According to theories of object-based attention, perception of unified objects depends on the binding together of the disparate features of each object via attention. Here we show that a visual feature that is not consciously perceived is nonetheless modulated by object-based attention: the influence of a subthreshold motion signal (prime) on subsequent motion perception depended critically on whether it was associated with the attended object or another, spatially overlapping object. These results show that invisibly weak features of attended objects are not lost, but are organized by and selected together with the object by attention.

Attention↗
PubMed1997

The motion analogue of the Café Wall illusion.

Detecting visual motion is computationally equivalent to detecting spatiotemporally oriented contours. The question addressed in this study is whether the illusory oriented contour in the space-space domain induces corresponding illusory motion perception. Two experiments were conducted. In experiment 1, the Café Wall pattern, which elicits a strong illusion of orientation (Café Wall illusion), was found to induce an illusion of motion when this pattern was converted to the space-time domain. The strength of the motion illusion depends on the mortar luminance and width, as for the Café Wall illusion. In experiment 2, the adaptation to this illusion of motion was found to induce a motion aftereffect in a static test, which indicates that a first-order-motion system contributes to the induction of the motion illusion. In fact, the motion-energy model was able to predict the strength of this motion aftereffect.

Computers↗
PubMed1999

Stages in motion processing revealed by the ocular following response.

Motion perception and associated involuntary eye movements depend on factors such as the physical attributes of the stimulus and visual attention. Cues from spatial changes in luminance (first-order motion in the Fourier domain) or more complicated transitions involving two-dimensional patterns (second-order, non-Fourier) require rather different kinds of analyses to detect their net motion. During a fixation task we monitored eye movements induced by the onset of motion to examine the functional properties of the monkey cortical motion processing system. Eye movement velocity was indistinguishable to first- and second-order motion; concomitant response latency confirmed an additional calculation is required to detect the direction and velocity of second-order motion.

Analysis of Variance↗
PubMed1988

Temporal properties of apparent motion in subjective figures.

In 'Kanizsa' figures, vivid subjective shapes are seen in the absence of explicit contours to define them. When two or more such figures are presented sequentially, so that the subjective shape occupies different positions, good apparent motion of the shape is usually reported. This motion percept must be mediated by a high-level process, in which form extraction precedes motion detection. Some spatial and temporal properties of this motion process are investigated. A major finding is that motion is only perceived when the time interval between successive frames falls below about 500 ms, and the duration of each frame exceeds about 80 ms.

Form Perception↗
PubMed1999

Anomalous perception of coherence and transparency in moving plaid patterns.

While the low-level processes mediating the detection of primary visual attributes are well understood, much less is known about the way in which these attributes are assigned to objects in the visual world. For example, when a region of the retinal image contains multiple motion signals at a range of spatial scales, how do we know whether these signals come from a single object or multiple objects? Here, we present data from four neurological patients on a psychophysical task requiring them to report whether the two components of a plaid pattern appear to move coherently or transparently. The spatial frequency of one component of the plaid is held constant while that of the other is manipulated. While some of the patients perceive coherent motion over a much smaller range of spatial frequencies than normal controls, others report coherence over almost the entire range tested. We discuss the implications of these findings for computational theories of motion perception and higher-level visual processing.

Adult↗
PubMed1977

Arthrokinetic nystagmus and ego-motion sensation.

A compelling illusion of body rotation and nystagmus can be induced when the horizontally extended arm of a stationary subject is passively rotated about a vertical axis in the shoulder joint. Lateral nystagmus with the fast phase beating in the opposite direction to the arm movement was found consistently; the mean slow phase velocity increased with increasing actual arm velocity and reached about 15 degrees/sec; the mean position of the eyes was deviated towards the fast phase as in optokinetic nystagmus, and the nystagmus continued after the cessation of stimulation (arthrokinetic after-nystagmus). The existence of an arthrokinetic circularvection and nystagmus indicates a convergence of vestibular and somatosensory afferents from joint receptors. It is concluded that information about joint movements plays an important role within the multisensory processes of self-motion perception.

Adult↗
PubMed1997

Pupil response triggered by the onset of coherent motion.

BACKGROUND: Recent studies have shown that transient constrictions of the pupil can be elicited by visual stimuli that do not cause an increment in light flux level on the retina. Such stimuli include achromatic gratings and isoluminant chromatic patterns. METHOD: We investigated pupillary responses to the onset of coherent movement generated in a pattern of dots in random motion. Measurements were carried out in normal observers and in a subject with hemianopia caused by damaged primary visual cortex. RESULTS: The experimental findings show that the onset of coherent motion triggers systematic constrictions of the pupil that cannot be accounted for in terms of a pupil light reflex response. We labelled these constrictions Pupil motion responses (PMRs). Results show that PMRs have large response latencies and on average are of small response amplitudes. The dependence of PMRs on changes in motion parameters such as stimulus speed and direction of motion has been investigated. CONCLUSIONS: The existence of PMRs to the onset of the coherent motion in human vision has been demonstrated. These new findings are discussed in relation to the psychophysical and physiological data on motion perception and the possible pathways involved in the control of the pupil response.

Hemianopsia↗
PubMed1994

Frames of reference and motion aftereffects.

Evidence concerning the origin of the motion aftereffect (MAE) is assessed in terms of a model of levels of representation in visual motion perception proposed by Wade and Swanston. Very few experiments have been designed so as to permit unambiguous conclusions to be drawn. The requirements for such experiments are identified. Whereas retinocentric motion could in principle give rise to the MAE, data are not available which would enable a conclusion to be drawn. There is good evidence for a patterncentric origin, indicating that the MAE is primarily the result of adaptation in the systems responsible for detecting relative visual motion. There is evidence for a further contribution from the process that compensates retinocentric motion for eye movements, in the form of nonveridical information for eye movements. There may also be an effect at the level at which perceived distance and self-movement information are combined with egocentric motion to give a geocentric representation which provides the basis for reports of phenomenal experience. It is concluded that the MAE can be caused by changes in activity at more than one level of representation, and cannot be ascribed to a single underlying process.

Eye Movements↗
PubMed2002

Coherent motion pops out during smooth pursuit.

Stimulus motion is a prominent feature that is used by the visual system to segment figure from ground and perceptually bind widely separated objects. Pursuit eye movements can be influenced by such perceptual grouping processes. We have examined the subjects' ability to detect small amounts of coherent motion in random dot kinematograms during pursuit. We compared performance on tests of coherent motion perception while subjects fixated a stationary spot or while they tracked a moving target. The results indicate that smooth pursuit can improve subjects' ability to detect the presence of coherent motion. We tentatively propose that an efference copy of the eye movement signal can enhance the ability of the visual system to detect correlations between sparsely placed targets among noisy distractors.

Artifacts↗
PubMed2006

The continuous wagon wheel illusion is associated with changes in electroencephalogram power at approximately 13 Hz.

Continuously moving objects sometimes appear to spontaneously reverse their motion direction. The mechanisms underlying this bistable phenomenon (the "continuous wagon wheel illusion") are heavily debated, but one interpretation suggests that motion information is perceived in discrete episodes at a rate between 10 and 15 Hz. Here, we asked observers to report the perceived direction of a continuously rotating wheel while 32-channel electroencephalogram (EEG) was recorded. We then separated periods of perceived true from illusory (reversed) motion and compared the EEG power spectrum under these two perceptually distinct yet physically identical conditions. The only reliable difference was observed approximately 13 Hz over centroparietal electrodes, independent of the temporal frequency of the wheel. Thus, it is likely to reflect internal processes rather than purely stimulus-driven activity. EEG power (13 Hz) decreased before the onset of illusory motion and increased before transitions back to real motion. Using this relationship, it was possible to predict above chance, on a trial-by-trial basis, the direction of the upcoming perceptual transition. These data are compatible with the idea that motion perception occurs in snapshots <100 ms in duration.

Adult↗
PubMed2005

Perception of opposite-moving dots in 3- to 5-month-old infants.

We conducted four experiments on the development of motion perception in a total of 109 3- to 5-month-old infants using motion stimuli consisting of opposite-moving dots. A psychophysical study showed that adult subjects perceived two global planes with opposite-moving dots, but this global perception collapsed when paired opposite-moving dots were located within 0.4 deg of one another (Qian, Andersen, & Adelson, 1994). We used this paired-dot stimulus as a non-target and the opponent motion stimulus as a target and examined target preference using methods based on forced-choice-preferential looking (Teller, 1979). In Experiment 1, we used 90 moving dots as stimuli. The results showed that 5-month-old infants had a significant preference for the targets but 4- and 3-month-olds did not. In Experiment 2, we used a small number of dots, and the results showed that 5-month-old infants did not prefer the target significantly. These results suggest that the preference for a target decreases according to the number of dots. In Experiment 3, we used opponent motion with long traveling length of the dots, and the results showed that all age groups, including 3-month-olds, had a preference for the moving targets. We showed that the preference observed in Experiment 3 was dependent not on local traveling length but on the global opponency. These results suggest that the perception of motion opponency based on a global motion cue emerges at 5 months of age (Experiments 1 and 2) and that the traveling length of the dots promote this perception (Experiments 3 and 4).

Child Development↗
PubMed2000

Hemifield visual motion stimulation: an example of interhemispheric crosstalk.

Coherent motion stimulation of the right or left visual hemifield was performed in nine healthy volunteers in order to investigate interhemispheric visuo-visual interaction by means of functional magnetic resonance imaging. The vertical edge of the motion pattern field was located 8 degrees distant from the fixation point to avoid stimulating the vertical meridian, which is represented retinotopically in both hemispheres. Bilateral activation was significant in the middle occipital gyrus (motion-sensitive middle temporal/middle superior temporal areas; BA 19/37). A negative signal change was found in the primary visual cortex including the lingual and fusiform gyri (BA 18/17) and the occipital white matter containing the optic radiation contralateral to the stimulated hemisphere. These data are most compatible with an interhemispheric transfer of visual motion information, most likely through the corpus callosum. Transcallosal transfer of visual motion information, evident as increases (BA 19/37) and decreases (BA 18/17) of the fMRI signals, may be functionally significant for the processing of motion perception.

Adult↗
PubMed1997

Dual multiple-scale processing for motion in the human visual system.

A number of psychophysical and physiological studies have suggested that first- and second-order motion signals are processed, at least initially, by independent pathways, and that the two pathways both consist of multiple motion-detecting channels that are each narrowly tuned to a different spatial scale (spatial frequency). However, the precise number and nature of the mechanisms that subserve first- and second-order motion perception in human vision remain both controversial and speculative. We sought to clarify this issue by conducting selective adaptation experiments, in which modulation-depth thresholds for identifying the direction of stimulus motion of first-order (luminance-defined) and second-order (contrast-defined) drifting gratings were measured both prior to and following adaptation to motion. The drift direction, spatial frequency and stimulus type (either first- or second-order) of the adaptation and test stimuli were systematically manipulated. When the adaptation and test stimuli were either both first-order gratings or both second-order gratings, robust elevations of direction-identification thresholds were found and, importantly, these aftereffects exhibited both direction-selectivity and spatial-frequency selectivity. Cross-over-adaptation effects between first- and second-order gratings were also sometimes observed, but were very weak and not spatial-frequency selective. These findings give direct support for the existence of multiple-scale processing for first- and second-order motion in the human visual system and provide additional evidence that the two varieties of motion are initially processed by independent pathways.

Adaptation, Ocular↗