Motion Processing System Research Articles

Devising a Multi-camera Motion Capture and Processing System for Production Plant Monitoring and Operator's Training in Virtual Reality

Devising a Multi-camera Motion Capture and Processing System for Production Plant Monitoring and Operator's Training in Virtual Reality

Prior Exposure to Dynamic Visual Displays Reduces Vection Onset Latency

While compelling illusions of self-motion (vection) can be induced purely by visual motion, they are rarely experienced immediately. This vection onset latency is thought to represent the time required to resolve sensory conflicts between the stationary observer's visual and nonvisual information about self-motion. In this study, we investigated whether manipulations designed to increase the weightings assigned to vision (compared to the nonvisual senses) might reduce vection onset latency. We presented two different types of visual priming displays directly before our main vection-inducing displays: (1) 'random motion' priming displays- designed to pre-activate general, as opposed to self-motion-specific, visual motion processing systems; and (2) 'dynamic no-motion' priming displays- designed to stimulate vision, but not generate conscious motion perceptions. Prior exposure to both types of priming displays was found to significantly shorten vection onset latencies for the main self-motion display. These experiments show that vection onset latencies can be reduced by pre-activating the visual system with both types of priming display. Importantly, these visual priming displays did not need to be capable of inducing vection or conscious motion perception in order to produce such benefits.

Interpretation of Swedish Sign Language Using Convolutional Neural Networks and Transfer Learning

The automatic interpretation of sign languages is a challenging task, as it requires the usage of high-level vision and high-level motion processing systems for providing accurate image perception. In this paper, we use Convolutional Neural Networks (CNNs) and transfer learning to make computers able to interpret signs of the Swedish Sign Language (SSL) hand alphabet. Our model consists of the implementation of a pre-trained InceptionV3 network, and the usage of the mini-batch gradient descent optimization algorithm. We rely on transfer learning during the pre-training of the model and its data. The final accuracy of the model, based on 8 study subjects and 9400 images, is 85%. Our results indicate that the usage of CNNs is a promising approach to interpret sign languages, and transfer learning can be used to achieve high testing accuracy despite using a small training dataset. Furthermore, we describe the implementation details of our model to interpret signs as a user-friendly web application.

EP-1632: A motion monitoring and processing system based on computer vision: prototype and proof of principle

EP-1632: A motion monitoring and processing system based on computer vision: prototype and proof of principle

The interaction between orientation and motion signals in moving oriented Glass patterns.

Previous psychophysical evidence suggests that motion and orientation processing systems interact asymmetrically in the human visual system, with orientation information having a stronger influence on the perceived motion direction than vice versa. To investigate the mechanisms underlying this motion-form interaction we used moving and oriented Glass patterns (GPs), which consist of randomly distributed dot pairs (dipoles) that induce the percept of an oriented texture. In Experiment 1 we varied the angle between dipole orientation and motion direction (conflict angle). In separate sessions participants either judged the orientation or motion direction of the GP. In addition, the spatiotemporal characteristics of dipole motion were manipulated as a way to limit (Experiment 1) or favor (Experiment 2) the availability of orientation signals from motion (motion streaks). The results of Experiment 1 showed that apparent GP motion direction is attracted toward dipole orientation, and apparent GP orientation is repulsed from GP motion. The results of Experiment 2 showed stronger repulsion effects when judging the GP orientation, but stronger motion streaks from the GP motion can dominate over the signals provided by conflicting dipole orientation. These results are consistent with the proposal that two separate mechanisms contribute to our perception of stimuli which contain conflicting orientation and motion information: (i) perceived GP motion is mediated by spatial motion-direction sensors, in which signals from motion sensors are combined with excitatory input from orientation-tuned sensors tuned to orientations parallel to the axis of GP motion, (ii) perceived GP orientation is mediated by orientation-tuned sensors which mutually inhibit each other. The two mechanisms are revealed by the different effects of conflict angle and dipole lifetime on perceived orientation and motion direction.

Children's Brain Responses to Optic Flow Vary by Pattern Type and Motion Speed.

Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG) responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction) at three different speeds (2, 4, and 8 deg/s). Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood.

The neural development of the biological motion processing system does not rely on early visual input

Naturally occurring sensory deprivation in humans provides a unique opportunity to identify sensitive phases for the development of neuro-cognitive functions. Patients who had experienced a transient period of congenital visual deprivation due to bilateral dense cataracts (congenital cataract, cc) have shown, after visual re-afferentation, deficits in a number of higher visual functions including global motion and face processing. By contrast, biological motion (BM) perception seemed to be spared. The present study investigated the neural correlates of BM processing in a sample of 12 congenital cataract-reversal individuals who had underwent visual restoration surgery at the age of a few months up to several years. The individual threshold for extracting BM from noise was assessed in a behavioral task while event-related potentials (ERPs) were recorded in response to point-light displays of a walking man and of a scrambled version of the same stimuli. The threshold of the cc group at detecting BM did not differ from that of a group of matched controls (mc). In both groups, the N1 was modulated by BM. These largely unimpaired neural responses to BM stimuli together with a lack of behavioral group differences suggest that, in contrast to the neural systems for faces the neural systems for BM processing specialize independent of early visual input.

Sensitivity of a harbor seal (Phoca vitulina) to coherent visual motion in random dot displays.

Motion vision is one of the fundamental properties of the visual system and is involved in numerous tasks. Previous work has shown that harbor seals are able to perceive visual motion. Tying in with this experimental finding, we assessed the sensitivity of harbor seals to visual motion using random dot displays. In these random dot displays, either all or a percentage of the dots plotted in the display area move into one direction which is referred to as percent coherence. Using random dot displays allows determining motion sensitivity free from form or position cues. Moreover, when reducing the lifetime of the dots, the experimental subjects need to rely on the global motion over the display area instead of on local motion events, such as the streaks of single dots. For marine mammals, the interpretation of global motion stimuli seems important in the context of locomotion, orientation and foraging. The first experiment required the seal to detect coherent motion directed upwards in one out of two stimulus displays and psychophysical motion coherence detection thresholds were obtained ranging from 5% to 35% coherence. At the beginning of the second experiment, which was conducted to reduce the differential flickering of the motion stimulus as secondary cue, the seal was directly able to transfer from coherent motion detection to a discrimination of coherent motion direction, leftward versus rightward. The seal performed well even when the duration of the local motion event was extremely short in the last experiment, in which noise was programmed as random position noise. Its coherence threshold was determined at 23% coherence in this experiment. This motion sensitivity compares well to the performance of most species tested so far excluding monkeys, humans and cats. To conclude, harbor seals possess an effective global motion processing system. For seals, the interpretation of global and coherent motion might e. g. play a role in the interpretation of optic flow information or when breaking the camouflage of cryptic prey items.

Neural representation of motion-in-depth in area MT.

Neural processing of 2D visual motion has been studied extensively, but relatively little is known about how visual cortical neurons represent visual motion trajectories that include a component toward or away from the observer (motion in depth). Psychophysical studies have demonstrated that humans perceive motion in depth based on both changes in binocular disparity over time (CD cue) and interocular velocity differences (IOVD cue). However, evidence for neurons that represent motion in depth has been limited, especially in primates, and it is unknown whether such neurons make use of CD or IOVD cues. We show that approximately one-half of neurons in macaque area MT are selective for the direction of motion in depth, and that this selectivity is driven primarily by IOVD cues, with a small contribution from the CD cue. Our results establish that area MT, a central hub of the primate visual motion processing system, contains a 3D representation of visual motion.

Motion‐onset visual evoked potentials ‐ Important tool in vision and eye research

AbstractPurpose Despite quite a long history of visual evoked potentials (VEPs), their use has been limited so far almost exclusively to flash or pattern related responses of the primary visual cortex (mediated mainly via activation of the parvocellular system of the visual pathway. It is surprising that efforts to extend it to more complex testing including an examination of the motion processing system (magnocellular system and dorsal stream) are quite rare (e.g. Kuba and Kubová, Doc Ophthalmol, 1992, 80, 83‐89; Kubová et al., 1995, Vision Res, 35, 197‐205.Methods Early or selective involvement of the motion processing system is suspected in many CNS disorders and we suggest that motion‐onset VEPs may recognize functional problems of this kind better than imagine techniques (Kuba et al., Vision Res, 2007, 47, 189‐202.Results Motion‐onset VEPs display latency shortening up to the age of about 18 years representing very slow individually different maturation of the motion processing system (Langrova et al., Vision Res., 2006, 46, 536‐544. In early adulthood they start accelerated latency prolongation when compared to pattern‐reversal, which might be a good indicator of individual biological ageing (Kuba et al., Vision Res, 2012, 62, 9‐16.Conclusion Since about 30% of pathological findings in our parallel pattern‐reversal and motion‐onset VEPs examinations in neuro‐ophthalmological patients display exclusively the motion‐onset VEPs pathology, we strongly recommend using them both in the theoretical vision research and ophthalmological diagnostics. Acknowledgement: Supported by the project PRVOUK ‐ P37/07.

Spectral inputs and ocellar contributions to a pitch-sensitive descending neuron in the honeybee

By measuring insect compensatory optomotor reflexes to visual motion, researchers have examined the computational mechanisms of the motion processing system. However, establishing the spectral sensitivity of the neural pathways that underlie this motion behavior has been difficult, and the contribution of the simple eyes (ocelli) has been rarely examined. In this study we investigate the spectral response properties and ocellar inputs of an anatomically identified descending neuron (DNII(2)) in the honeybee optomotor pathway. Using a panoramic stimulus, we show that it responds selectively to optic flow associated with pitch rotations. The neuron is also stimulated with a custom-built light-emitting diode array that presented moving bars that were either all-green (spectrum 500-600 nm, peak 530 nm) or all-short wavelength (spectrum 350-430 nm, peak 380 nm). Although the optomotor response is thought to be dominated by green-sensitive inputs, we show that DNII(2) is equally responsive to, and direction selective to, both green- and short-wavelength stimuli. The color of the background image also influences the spontaneous spiking behavior of the cell: a green background produces significantly higher spontaneous spiking rates. Stimulating the ocelli produces strong modulatory effects on DNII(2), significantly increasing the amplitude of its responses in the preferred motion direction and decreasing the response latency by adding a directional, short-latency response component. Our results suggest that the spectral sensitivity of the optomotor response in honeybees may be more complicated than previously thought and that ocelli play a significant role in shaping the timing of motion signals.

Aging effect in pattern, motion and cognitive visual evoked potentials

An electrophysiological study on the effect of aging on the visual pathway and various levels of visual information processing (primary cortex, associate visual motion processing cortex and cognitive cortical areas) was performed. We examined visual evoked potentials (VEPs) to pattern-reversal, motion-onset (translation and radial motion) and visual stimuli with a cognitive task (cognitive VEPs – P300 wave) at luminance of 17cd/m2. The most significant age-related change in a group of 150 healthy volunteers (15–85years of age) was the increase in the P300 wave latency (2ms per 1year of age). Delays of the motion-onset VEPs (0.47ms/year in translation and 0.46ms/year in radial motion) and the pattern-reversal VEPs (0.26ms/year) and the reductions of their amplitudes with increasing subject age (primarily in P300) were also found to be significant. The amplitude of the motion-onset VEPs to radial motion remained the most constant parameter with increasing age. Age-related changes were stronger in males.Our results indicate that cognitive VEPs, despite larger variability of their parameters, could be a useful criterion for an objective evaluation of the aging processes within the CNS. Possible differences in aging between the motion-processing system and the form-processing system within the visual pathway might be indicated by the more pronounced delay in the motion-onset VEPs and by their preserved size for radial motion (a biologically significant variant of motion) compared to the changes in pattern-reversal VEPs.

Do infants use a generalised motion processing system for discriminating facial motion

Abstract presented at The 28th European Conference on Visual Perception, 22-26 August 2005, A Coruna, Spain

Visual evoked potentials to pattern, motion and cognitive stimuli in Alzheimer’s disease

The aim of our study was to verify reported visual dysfunctions of patients with Alzheimer disease with the use of several variants of VEPs and visual ERPs and to learn whether these methods can be useful in diagnostics of AD. We tested 15 patients (6 women and 9 men, aged from 58 to 87) with mild to moderate Alzheimer disease (12-23 points of Mini Mental State Examination) and 15 age, gender and education level matched controls. The examination consisted of VEPs to pattern-reversal and motion-onset stimulation (to translational and radial movement) and of visual ERPs recorded during an odd-ball test. The subjects were instructed to signalize target stimuli by pressing of a button, which enabled to evaluate also the reaction time. While pattern-reversal VEPs were comparable in patients and controls, there were significantly smaller N2 peak amplitudes of motion-onset VEPs in patients with AD (in particular in radial moving stimuli outside the central 20 deg of the visual field), which suggests a dysfunction of the motion-processing (magnocellular) system or the dorsal cortical stream. ERPs, having significantly longer latencies in patients than in controls, distinguished well both groups. However, the individual AD diagnostics based on ERPs seems to be limited by rather high inter-individual variability of the ERP latencies. The ERPs might, however, be useful in disease progress and therapy effect estimation. Electrophysiological parameters did not correlate with neuropsychological ADAS cog test (Alzheimer Disease Assessment Scale--cognitive part).

Working memory, deafness and sign language

Working memory (WM) for sign language has an architecture similar to that for speech-based languages at both functional and neural levels. However, there are some processing differences between language modalities that are not yet fully explained, although a number of hypotheses have been mooted. This article reviews some of the literature on differences in sensory, perceptual and cognitive processing systems induced by auditory deprivation and sign language use and discusses how these differences may contribute to differences in WM architecture for signed and speech-based languages. In conclusion, it is suggested that left-hemisphere reorganization of the motion-processing system as a result of native sign-language use may interfere with the development of the order processing system in WM.

Amblyopic perception of biological motion

Although a number of low-level visual deficits in amblyopia have been identified, it is still unclear to what extent these deficits extend throughout the visual processing hierarchy. Biological motion perception can be a useful measure of local and global visual processing since the point-light stimuli that are often used to study this ability carry both local motion and global form information. To investigate the integrity of the biological motion processing system in amblyopia, we employed both detection and discrimination tasks with coherent or scrambled point-light walkers either alone or embedded in different types of point-light masks. These manipulations allowed for control over the amount of form and/or motion information available to the observers that could be used for task performance. We found that amblyopic eyes could process both the global form and local motion components of point-light walkers, indicating intact processing for these stimuli. However, amblyopic eyes did show an increased susceptibility to the addition of masking dots suggesting that segregation of signal from noise is deficient in amblyopia.

Development of cortical responses to optic flow

Humans discriminate approaching objects from receding ones shortly after birth, and optic flow associated with self-motion may activate distinctive brain networks, including the human MT+ complex. We sought evidence for evoked brain activity that distinguished radial motion from other optic flow patterns, such as translation or rotation by recording steady-state visual evoked potentials (ssVEPs), in both adults and 4-6 month-old infants to direction-reversing optic flow patterns. In adults, radial flow evoked distinctive brain responses in both the time and frequency domains. Differences between expansion/contraction and both translation and rotation were especially strong in lateral channels (PO7 and PO8), and there was an asymmetry between responses to expansion and contraction. In contrast, infants' evoked response waveforms to all flow types were equivalent, and showed no evidence of the expansion/contraction asymmetry. Infants' responses were largest and most reliable for the translation patterns in which all dots moved in the same direction. This pattern of response is consistent with an account in which motion processing systems detecting locally uniform motion develop earlier than do systems specializing in complex, globally non-uniform patterns of motion, and with evidence suggesting that motion processing undergoes prolonged postnatal development.

Signaling against the Wind: Modifying Motion-Signal Structure in Response to Increased Noise

Animal signals are optimized for particular signaling environments [1-3]. While signaling, senders often choose favorable conditions that ensure reliable detection and transmission [4-8], suggesting that they are sensitive to changes in signal efficacy. Recent evidence has also shown that animals will increase the amplitude or intensity of their acoustic signals at times of increased environmental noise [9-11]. The nature of these adjustments provides important insights into sensory processing. However, only a single piece of correlative evidence for signals defined by movement suggests that visual-signal design depends on ambient motion noise [12]. Here we show experimentally for the first time that animals communicating with movement will adjust their displays when environmental motion noise increases. Surprisingly, under sustained wind conditions, the Australian lizard Amphibolurus muricatus changed the structure and increased the duration of its introductory tail flicking, rather than increasing signaling speed. The way these lizards restructure the alerting component of their movement-based aggressive display in the presence of increased motion noise highlights the challenge we face in understanding motion-detection mechanisms under natural operating conditions.

Recovery from object substitution masking induced by transient suppression of visual motion processing: A repetitive transcranial magnetic stimulation study.

Object substitution masking is a form of visual backward masking in which a briefly presented target is rendered invisible by a lingering mask that is too sparse to produce lower image-level interference. Recent studies suggested the importance of an updating process in a higher object-level representation, which should rely on the processing of visual motion, in this masking. Repetitive transcranial magnetic stimulation (rTMS) was used to investigate whether functional suppression of motion processing would selectively reduce substitution masking. rTMS-induced transient functional disruption of cortical area V5/MT+, which is important for motion analysis, or V1, which is reciprocally connected with V5/MT+, produced recovery from masking, whereas sham stimulation did not. Furthermore, masking remained undiminished following rTMS over the region 2 cm posterior to V5/MT+, ruling out nonspecific effects of real stimulation and confirming regional specificity of the rTMS effect. The results suggest that object continuity via the normal function of the visual motion processing system might in part contribute to this masking. The relation of these findings to the reentrant processing view of object substitution masking and other visual phenomena is discussed.

Motion-onset VEPs: Characteristics, methods, and diagnostic use

This review article summarises the research on the motion-onset visual evoked potentials (VEPs) and important motion stimulus parameters which have been clarified. For activation of the visual motion processing system and evocation of the motion-onset specific N2 peak (with latency of 160–200 ms) from the extra-striate temporo-occipital and/or parietal cortex, the following stimulus parameters can be recently recommended: low luminance (<ca. 20 cd/m 2) and low contrast (<ca. 10%—sinusoidally modulated) of a moving structure with low velocity and temporal frequency (<ca. 6 Hz). A short (up to 200 ms) duration of motion and a long (at least 1 s) inter-stimulus interval reduce adaptation to motion and predominance of a pattern-related P1 peak. Radial motion (with increasing velocity and decreasing spatial frequency towards the periphery) produces larger reactions as compared to a unidirectional translation. In view of the slow maturation (up to the age of 18 years) and early ageing of the visual motion processing system, the use of age-dependent latency norms may be necessary. Since early or selective involvement of the motion processing system is suspected in some CNS disorders, we suggest an evaluation of the utility of motion-onset VEPs as part of the electrophysiological CNS examination since this method may recognise motion processing involvement better than other methods. Motion-onset VEPs might increase the sensitivity of this examination for diagnosing CNS diseases including Multiple Sclerosis, Neuroborreliosis, Glaucoma, Dyslexia and Encephalopathies.