Visual Motion Stimuli Research Articles

Measurement of generalization fields for the recognition of biological motion

The human visual system processes complex biological motion stimuli with high sensitivity and selectivity. The characterization of spatio-temporal generalization in the perception of biological motion is still a largely unresolved problem. We present an experiment that investigates how the visual system responds to motion stimuli that interpolate spatio-temporally between natural biological motion patterns. Inspired by analogous studies in stationary object recognition, we generated stimuli that interpolate between natural perceptual categories by morphing. Spatio-temporal morphs between natural movement patterns were obtained with a technique that allows to calculate linear combinations of spatio-temporal patterns. The weights of such linear combinations define a linear metric space over the set of generated movement patterns, so that the spatio-temporal similarity of the motion patterns can be quantified. In our experiments, we found smooth and continuous variation of the categorization probabilities with the weights of the prototypes in the morphs. For bipedal locomotion patterns we could accurately predict the perceived properties of the morphs by linear combinations of the perceived properties of the prototypes. Such predictions were not possible for morphs between locomotion and very dissimilar movements. We conclude that the visual system shows generalization within classes of motion patterns with similar basic structure, such as bipedal locomotion.

Visual motion stimulation, but not visually induced perception of self-motion, biases the perceived direction of verticality

Large-field torsional optokinetic stimulation is known to affect the perceived direction of gravity with verticality judgements deviating towards the direction of visual stimulus rotation. The present study aimed to replicate this effect and to examine it further by subjecting participants to optokinetic stimulation in roll, resulting in spontaneous alternations between the perception of object-motion and that of contradirectional self-motion (vection), as reported by the subjects. Simultaneously, subjects were oscillated laterally in a flight simulator and indicated their perception of postural verticality. Results confirmed that rotation of the visual environment in the frontal plane biases the perceived orientation of gravity towards the direction of visual stimulus motion. However, no differential effect of perceptual state on postural verticality was obtained when contrasting verticality judgements made during the perception of object-motion with those obtained during reported self-motion perception. This finding is likely to reflect a functional segregation of central nervous visual–vestibular subsystems that process the perception of self-tilt and that of self-rotation to some degree independently.

Stimulus size selectivity and receptive field organization of ectostriatal neurons in the pigeon.

The avian ectostriatum is the telencephalic recipient zone of the tectofugal pathway, which may be homologous to the colliculo-pulvinar-cortical pathway in mammals. The present paper studies the visual response properties and receptive field organization of ectostriatal cells in pigeons with extracellular recording and computer mapping techniques. The results indicate that 90% of ectostriatal cells prefer forward, downward and upward motion of visual stimuli at velocities in the range of 16-128 degrees s(-1). They respond optimally to small stimuli (1-4 degrees visual angle), mostly preferring a target of 2 degrees. Most cells (78.8%) have one excitatory receptive field that usually possesses one or two hotspots, some cells (13.5%) have two excitatory receptive fields each having one or two hotspots, and a few cells (7.7%) have one excitatory receptive field with an unresponsive region in the center. An inhibitory receptive field is not found surrounding the excitatory receptive field in the ectostriatal cells examined. These response properties and receptive field organization may reflect the possible roles of the ectostriatum in stimulus discrimination and visual cognition.

Cortical magnetic responses during linear apparent self motion

Electrophysiological studies in monkeys identified region of cerebral cortex that receive vestibular inputs including poserior part of the insula (parieto-insular vestibular cortex: PIVC), portions of the intraparietal sulcus (area 2~). and the central sulcus (area 3aV). Some past studies demonstrated that sensations of apparent whole body rotation also activate these regions. The information of whole body rotation is received by semicircular canals. On the other hand, the information of whole-body linear motion is received by otolith receptors, and its cortical processes are still unclear. In this study, the cortical sites that process sensations of linear apparent self motion (linear vection) were studied using neuromagnetic measurements. Brain magnetic fields evoked by visual motion stimuli were measured in 7 healthy volunteers (6 males, 22-34 years, right-handed, normal or corrected-to-normal vision), who reported they experienced sensation of apparent motion during measurements. Measurements of magnetic fields were carried out using 122ch whole-head neuromagnetometer (Neuromag-122TM) in a magnetically shielded room. Following white expanding stimuli (maximum size: 21*10.5 degrees) were presented on the black screen. (a) a rectangle expanding at 5.3 &g/s, 71.4 %, (b:vection stimulus) a rectangle expanding at 26.5 deg/s, 14.3 8, (c: control stimuli) a circle expanding at 5.3 deg/s, 14.3 %. The activated cortical areas were determined by first localizing single equivalent current dipoles (ECDs) in various local regions of a spherical head model. Among the calculated ECDs, those having a goodness-of-fit > 80% and with a 95%-confidence volume < 2000 mm3 were selected. The localization of ECDs was based on the spherical conductor model, which takes into account the volume current within the sphere. For both the vection and the control stimuli, the activation of post-central gyms (100 200 ms), infero-posterior temporal lobe (300 500 ms), lingual/fusiform gyrus (300 500 ms) were found. On the other hand, activations in posterior insula (300 400 ms), posterior operculum (400 500 ms). parietal lobule (300 500 ms), pre-central gyrus (300 400 ms), superir temporal gyms (400 500 ms) were observed for only vection stimulus. These areas are recognized as human analogs of vestibular cortex identified by former studies in monkey. The results also suggest these areas integrate multi-modal information.

Calibrating Visual Path Integration in VEs

When moving around in the world, humans can use the motion sensations provided by their kinesthetic, vestibular, and visual senses to maintain their sense of direction. Previous research in virtual environments (VEs) has shown that this so-called path integration process is inaccurate in the case that only visual motion stimuli are present, which may lead to disorientation. In an experiment, we investigated whether participants can calibrate this visual path integration process for rotations; in other words, can they learn the relation between visual flow and the angle that they traverse in the VE? Results show that, by providing participants with knowledge of results (KR), they can indeed calibrate the biases in their path integration process, and also maintain their improved level of performance on a retention test the next day.

Two classes of visual motion sensitive interneurons differ in direction and velocity dependency of in vivo calcium dynamics.

Neurons exploit both membrane biophysics and biochemical pathways of the cytoplasm for dendritic integration of synaptic input. Here we quantify the tuning discrepancy of electrical and chemical response properties in two kinds of neurons using in vivo visual stimulation. Dendritic calcium concentration changes and membrane potential of visual interneurons of the fly were measured in response to visual motion stimuli. Two classes of tangential cells of the lobula plate were compared, HS-cells and CH-cells. Both neuronal classes are known to receive retinotopic input with similar properties, yet they differ in morphology, physiology, and computational context. Velocity tuning and directional selectivity of the electrical and calcium responses were investigated. In both cell classes, motion-induced calcium accumulation did not follow the early transient of the membrane potential. Rather, the amplitude of the calcium signal seemed to be related to the late component of the depolarization, where it was close to a steady state. Electrical and calcium responses differed with respect to their velocity tuning in CH-cells, but not in HS-cells. Furthermore, velocity tuning of the calcium response, but not of the electrical response differed between neuronal classes. While null-direction motion caused hyperpolarization in both classes, this led to a calcium decrement in CH-cells, but had no effect on the calcium signal in HS-cells, not even when calcium levels had been raised by a preceding excitatory motion stimulus. Finally, the voltage-[Ca2+]i-relationship for motion-induced, transient potential changes was steeper and less rectifying in CH-cells than in HS-cells. These results represent an example of dendritic information processing in vivo, where two neuronal classes respond to identical stimuli with a similar electrical response, but differing calcium response. This highlights the capacity of neurons to segregate two response components.

Processing of irrelevant visual motion during performance of an auditory attention task

The extent to which irrelevant perception of visual motion distractors can be modulated by manipulating auditory load in a relevant task was assessed with Positron Emission Tomography (PET) and behavioural experiments. Subjects performed an auditory task and ignored an irrelevant visual motion stimulus, under two conditions. In a low load condition, subjects were asked to detect words spoken in a loud voice among words spoken in a quiet voice, while in a high load condition they attempted to detect bisyllabic words among monosyllabic and trisyllabic words. We found that motion-related visual areas were strongly activated by the irrelevant motion stimulus, compared to a static stimulus, under both conditions of load in the auditory task. In a second behavioural experiment, the duration of the motion after-effect was similarly unaffected by adaptation under low or high auditory load. These results are in clear contrast with the strong modulation of irrelevant motion processing by visual load, as reflected in the duration of the motion after effect ( Section 6) and neural responses in motion-related visual areas (Rees et al., Science, (1997) 278, 338). These findings support the claim that attentional capacity is restricted within but not between sensory modalities, and indicate that processing of visual distractors may occur whenever there is sufficient visual capacity to process them, despite being task- and modality-irrelevant.

Cholinergic and GABAergic pathways in fly motion vision

BackgroundThe fly visual system is a highly ordered brain structure with well-established physiological and behavioral functions. A large number of interneurons in the posterior part of the third visual neuropil, the lobula plate tangential cells (LPTCs), respond to visual motion stimuli. In these cells the mechanism of motion detection has been studied in great detail. Nevertheless, the cellular computations leading to their directionally selective responses are not yet fully understood. Earlier studies addressed the neuropharmacological basis of the motion response in lobula plate interneurons. In the present study we investigated the distribution of the respective neurotransmitter receptors in the fly visual system, namely nicotinic acetylcholine receptors (nAChRs) and GABA receptors (GABARs) demonstrated by antibody labeling.ResultsThe medulla shows a laminar distribution of both nAChRs and GABARs. Both receptor types are present in layers that participate in motion processing. The lobula also shows a characteristic layering of immunoreactivity for either receptor in its posterior portion. Furthermore, immunostaining for nAChRs and GABARs can be observed in close vicinity of lobula plate tangential cells. Immunostaining of GABAergic fibers suggests that inhibitory inputs from the medulla are relayed through the lobula to the lobula plate rather than through direct connections between medulla and lobula plate.ConclusionsThe interaction of excitatory and inhibitory pathways is essential for the computation of visual motion responses and discussed in the context of the Reichardt model for motion detection.

The multiple roles of visual cortical areas MT/MST in remembering the direction of visual motion.

Although the role of cortical areas MT and MST (MT/MST) in the processing of directional motion information is well established, little is known about the way these areas contribute to the execution of complex behavioral tasks requiring the use of such information. We tested monkeys with unilateral lesions of these areas on a visual working memory task in which motion signals not only had to be encoded, but also stored for brief periods of time and then retrieved. The monkeys compared the directions of motion of two random-dot stimuli, sample and test, separated by a temporal delay. By increasing the temporal delay and spatially separating the two stimuli, placing one in the affected visual field and the other in the intact visual field, we were able to assess the contribution of MT/MST to specific components of the task: encoding (sample), retention (delay) and encoding/retrieval/comparison (test). We found that the effects of MT/MST lesions on specific components depended upon the demands of the task and the nature of the visual motion stimuli. Whenever stimuli consisted of random dots moving in a broad range of directions, MT/MST lesions appeared to affect encoding. Furthermore, when the lesions affected encoding of the sample, retention of the direction of stimulus motion was also affected. However, when the stimulus was coherent and the emphasis of the task was on the comparison of small direction differences, the absence of MT/MST had major impact on the retrieval/comparison component of the task and not on encoding or storage.

Source localization of visually evoked magnetic fields to stimuli in apparent motion

When at least two spatially separated visual stimuli are delivered sequentially under appropriate temporal conditions, a continuous moving sensation, which is called apparent motion, can be perceived. To investigate the cortical activation associated with visual apparent motion, brain evoked magnetic fields in response to visual half field apparent motion stimuli were measured using a whole-head magnetometer. Peak magnetic fields were observed in the latency range of 170-190 msec after the stimulus onset. The neural sources in this epoch were estimated to lie in the border between occipital and temporal areas in the contralateral hemisphere, which corresponds to the extrastriate visual cortex, including the middle temporal area. The results suggest that the activities in the extrastriate cortex reflect apparent motion perception.

Human brain regions responsive to visual motion stimuli: determination by magnetoencephalography and three dimensional MRI

Human brain regions responsive to visual motion stimuli: determination by magnetoencephalography and three dimensional MRI

Motion and stereoscopic tilt perception

Abstract— Stereoscopic perception of tilt about a vertical or horizontal axis is influenced by size and shear disparities, respectively. Other researchers have reported that, under certain conditions, stereoscopic perception deficits occur when the dots in a random‐dot stereogram move at a velocity that produces optokinetic nystagmus. Here we examine how size disparity and shear disparity affect stereoscopic tilt perception under various motion conditions. We hypothesized that visual stimulus motion may interact with these disparities to affect tilt perception. Our results indicate that shear disparity and size disparity effects under static conditions are maintained under motion conditions. A possible explanation for the conflict between the current and previous results is discussed, as are implications for binocular head‐mounted display applications.

The interaction of otolith and proprioceptive information in the perception of verticality. The effects of labyrinthine and CNS disease.

A review of recent experiments in patients with labyrinthine and neurological disorders assessing the subjective postural vertical (SPV) and the subjective visual vertical (SVV) is presented. The SPV was measured with subjects (Ss) seated in a motorized flight simulator tilting at 1.5 deg/s in roll and pitch; the Ss' task was to indicate when they entered and left self-verticality. The SVV was measured by Ss adjusting a straight line to what they perceived as gravitational upright. Clear dissociations between the SVV and SPV were found, for example, patients with acute unilateral vestibular disorders had marked tilts of the SVV toward the side of the lesion but a "lean" (bias, tilt) of the SPV was never found. Dissociations of the SPV and SVV could also be induced in normal subjects by roll-plane visual motion stimuli: the SVV was tilted in the direction of motion, but the SPV was not. Prolonged lateral body tilt did, however, bias the SVV (the "A" effect) and the SPV, but these effects are likely to be mediated by somatosensory rather than otolithic input. Evidence for the latter came from (i) findings in patients with absent vestibular function, who showed an enhanced "A" effect, and (ii) from a patient with a thalamic infarction, who showed absence of the "A" effect when leaning on the hemihypesthetic side. In separate experiments where normal Ss indicated space-vertical and space-horizontal with saccadic eye movements, we found differences between these percepts, that is, subjective external space lost orthogonality. The findings in these various experiments can be interpreted if we abandon the idea of a single, "internal representation" of verticality. Different sensory modalities convey different and sometimes conflicting messages about verticality. Otolithic and somatosensory signals can have opposite sign effects during verticality estimates while tilted. In man, somatosensory cues have a prominent role in verticality perception.

Brain location and visual topography of cortical area V6A in the macaque monkey.

The brain location, extent and functional organization of the cortical visual area V6A was investigated in macaque monkeys by using single cell recording techniques in awake, behaving animals. Six hemispheres of four animals were studied. Area V6A occupies a horseshoe-like region of cortex in the caudalmost part of the superior parietal lobule. It extends from the medial surface of the brain, through the anterior bank of the parieto-occipital sulcus, up to the most lateral part of the fundus of the same sulcus. Area V6A borders on areas V6 ventrally, PEc dorsally, PGm medially and MIP laterally. Of 1348 neurons recorded in V6A, 61% were visual and 39% non-visual in nature. The visual neurons were particularly sensitive to orientation and direction of movement of visual stimuli. The inferior contralateral quadrant was the most represented one. Visual receptive fields were also found in the inferior ipsilateral quadrant and in the upper visual field. Receptive fields were on average smaller in the lower visual field than in the upper one. Both central and peripheral parts of the visual field were represented. Large parts of the visual field were represented in small regions of area V6A, and the same regions of the visual field were re-represented many times in different parts of this area, without any apparent topographical order. The only reliable sign of retinotopic organization was the predominance of central representation dorsally and far periphery ventrally. The functional organization of area V6A is discussed in the view that this area could be involved in the control of reaching out and grasping objects.

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°/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.

The intrinsic electrophysiological characteristics of fly lobula plate tangential cells: III. Visual response properties.

In this last paper in a series (Borst and Haag, 1996; Haag et al., 1997) about the lobula plate tangential cells of the fly visual system (CH, HS, and VS cells), the visual response properties were examined using intracellular recordings and computer simulations. In response to visual motion stimuli, all cells responded mainly by a graded shift of their axonal membrane potential. While ipsilateral motion resulted in a graded membrane potential shift, contralateral motion led to distinct EPSPs. For HS cells, simultaneous extracellular recorded action potentials of a spiking interneuron, presumably the H2 cell, corresponded to the EPSPs in the HS cell in a one-to-one fashion. When HS cells were hyperpolarized during ipsilateral motion, they mainly produced action potentials, but when they were hyperpolarized during contralateral motion only a slight increase of EPSP amplitude, could be observed. Intracellular application of the sodium channel blocker QX 314 abolished action potentials of HS cells while having little effect on the graded membrane response to ipsilateral motion. HS and CH cells were also studied with respect to their spatial integration properties. For both cell types, their graded membrane response was found to increase less than linearly with the size of the ipsilateral motion pattern. However, while for HS cells various amounts of hyperpolarizing current injected during motion stimulation led to different saturation levels, this was not the case for CH cells. In response to a sinusoidal velocity modulation, CH cells followed pattern motion only up to 10 Hz modulation frequency, but HS cells still revealed significant membrane depolarizations up to about 40 Hz. In the computer simulations, the compartmental models of tangential cells, as derived in the previous papers, were linked to an array of local motion detectors. The model cells revealed the same basic response features as their natural counterparts. They showed a response saturation as a function of stimulus size. In CH-models, however, the saturation was less pronounced than in real CH-cells, indicating spatially nonuniform membrane resistances with higher values in the dendrite. As in the experiments, HS models responded to high-frequency velocity modulation with a higher amplitude than did CH models.

Oscillopsia: visual function during motion in the absence of vestibulo-ocular reflex

OBJECTIVESTo investigate (1) the effects of loss of vestibular function on spatiotemporal vision and (2) the mechanisms which enable labyrinthine defective (LD) patients to adapt to oscillopsia.METHODSVisual function and eye...

Roll motion stimuli: sensory conflict, perceptual weighting and motion sickness

In an experiment with 17 subjects, interactions of visual roll motion stimuli and vestibular body tilt stimuli were examined in determining the subjective vertical. Interindividual differences in weighting the visual information were observed, but in general, visual and vestibular responses added in setting the vertical. Despite the conflicting sensory information, motion sickness was not reported apart from one subject on one single occasion. This is in conflict with the sensory mismatch theory on motion sickness, but in agreement with the subjective vertical conflict theory.

Active Membrane Properties and Signal Encoding in Graded Potential Neurons

We investigated the influence of active membrane properties on the precision by which the stimulus velocity is encoded in the membrane potential of a motion-sensitive interneuron in the blowfly. The so-called HS-cells respond to visual motion stimuli with a graded shift in membrane potential. Superimposed on this graded response are small spike-like events. This "mixed" visual response mode can be modified by current injection in two different ways. (1) By ongoing injection of hyperpolarizing current, the spike-like events are turned into full-blown action potentials, and (2) by injection of depolarizing current, the spike-like events become completely suppressed. The visual response then consists of a graded shift of membrane potential only. As a measure of the fidelity, we calculated the coherence between the motion stimulus and the response of the cell elicited with different electrical manipulations of the cell. We found that the coherence was highest for the cell at rest. Any electrical manipulation resulted in a reduced coherence. This was attributable partly to a lower signal-to-noise ratio and partly to an increased nonlinearity in the response. By applying a threshold operation we transformed the analog membrane response into an all-or-none spike train. A comparison between these two ways of signal representation revealed that more information about the stimulus velocity is inherent in the analog membrane potential than in the spike train.

Reciprocal inhibitory visual-vestibular interaction. Visual motion stimulation deactivates the parieto-insular vestibular cortex.

The vestibular system--a sensor of head accelerations--cannot detect self-motion at constant velocity and thus requires supplementary visual information. The perception of self-motion during constant velocity movement is completely dependent on visually induced vection. This can be linear vection or circular vection (CV). CV is induced by large-field visual motion stimulation during which the stationary subject perceives the moving surroundings as being stable and himself as being moved. To determine the unknown cortical visual-vestibular interaction during CV, we conducted a PET activation study on CV in 10 human volunteers. The PET images of cortical areas activated during visual motion stimulation without CV were compared with those with CV. Hitherto, CV was explained neurophysiologically by visual-vestibular convergence with activation of the vestibular nuclei, thalamic subnuclei and vestibular cortex. If CV were mediated by the vestibular cortex, one would expect that an adequate visual motion stimulus would activate both the visual and vestibular cortex. Contrary to this expectation, it was shown for the first time that visual motion stimulation with CV not only activates a medial parieto-occipital visual area bilaterally, separate from middle temporal/medial superior temporal areas, it also simultaneously deactivates the parieto-insular vestibular cortex. There was a positive correlation between the perceived intensity of CV and relative changes in regional CBF in parietal and occipital areas. These findings support a new functional interpretation: reciprocal inhibitory visual-vestibular interaction as a multisensory mechanism for self-motion perception. Inhibitory visual-vestibular interaction might protect visual perception of self-motion from potential vestibular mismatches caused by involuntary head accelerations during locomotion, and this would allow the dominant sensorial weight during self-motion perception to shift from one sensory modality to the other.