Motion Stimuli Research Articles

Poor fixation stability does not account for motion perception deficits in amblyopia

People with amblyopia show deficits in global motion perception, especially at slow speeds. These observers are also known to have unstable fixation when viewing stationary fixation targets, relative to healthy controls. It is possible that poor fixation stability during motion viewing interferes with the fidelity of the input to motion-sensitive neurons in visual cortex. To probe these mechanisms at a behavioral level, we assessed motion coherence thresholds in adults with amblyopia while measuring fixation stability. Consistent with prior work, participants with amblyopia had elevated coherence thresholds for the slow speed stimuli, but not the fast speed stimuli, using either the amblyopic or the fellow eye. Fixation stability was elevated in the amblyopic eye relative to controls across all motion stimuli, and not selective for conditions on which perceptual deficits were observed. Fixation stability was not related to visual acuity, nor did it predict coherence thresholds. These results suggest that motion perception deficits might not be a result of poor input to the motion processing system due to unstable fixation, but rather due to processing deficits in motion-sensitive visual areas.

Distinct detection and discrimination sensitivities in visual processing of real versus unreal optic flow.

We examined the intricate mechanisms underlying visual processing of complex motion stimuli by measuring the detection sensitivity to contraction and expansion patterns and the discrimination sensitivityto the location of the center of motion (CoM) in various real and unreal optic flow stimuli. We conducted two experiments (N = 20 each) and compared responses to both "real" optic flow stimuli containing information about self-movement in a three-dimensional scene and "unreal" optic flow stimuli lacking such information. We found that detection sensitivity to contraction surpassed that to expansion patterns for unreal optic flow stimuli, whereas this trend was reversed for real optic flow stimuli. Furthermore, while discrimination sensitivity to the CoM location was not affected by stimulus duration for unreal optic flow stimuli, it showed a significant improvement when stimulus duration increased from 100 to 400 ms for real optic flow stimuli. These findings provide compelling evidence that the visual system employs distinct processing approaches for real versus unreal optic flow even when they are perfectly matched for two-dimensional global features and local motion signals. These differences reveal influences of self-movement in natural environments, enabling the visual system to uniquely process stimuli with significant survival implications.

Linking neural population formatting to function.

Animals capable of complex behaviors tend to have more distinct brain areas than simpler organisms, and artificial networks that perform many tasks tend to self-organize into modules (1-3). This suggests that different brain areas serve distinct functions supporting complex behavior. However, a common observation is that essentially anything that an animal senses, knows, or does can be decoded from neural activity in any brain area (4-6). If everything is everywhere, why have distinct areas? Here we show that the function of a brain area is more related to how different types of information are combined (formatted) in neural representations than merely whether that information is present. We compared two brain areas: the middle temporal area (MT), which is important for visual motion perception (7, 8), and the dorsolateral prefrontal cortex (dlPFC), which is linked to decision-making and reward expectation (9,10)). When monkeys based decisions on a combination of motion and reward information, both types of information were present in both areas. However, they were formatted differently: in MT, they were encoded separably, while in dlPFC, they were represented jointly in ways that reflected the monkeys' decision-making. A recurrent neural network (RNN) model that mirrored the information formatting in MT and dlPFC predicted that manipulating activity in these areas would differently affect decision-making. Consistent with model predictions, electrically stimulating MT biased choices midway between the visual motion stimulus and the preferred direction of the stimulated units (11), while stimulating dlPFC produced 'winner-take-all' decisions that sometimes reflected the visual motion stimulus and sometimes reflected the preference of the stimulated units, but never in between. These results are consistent with the tantalizing possibility that a modular structure enables complex behavior by flexibly reformatting information to accomplish behavioral goals.

Target interception in virtual reality is better for natural versus unnatural trajectory shapes and orientations.

Human performance in perceptual and visuomotor tasks is enhanced when stimulus motion follows the laws of gravitational physics, including acceleration consistent with Earth's gravity, g. Here we used a manual interception task in virtual reality to investigate the effects of trajectory shape and orientation on interception timing and accuracy. Participants punched to intercept a ball moving along one of four trajectories that varied in shape (parabola or tent) and orientation (upright or inverted). We also varied the location of visual fixation such that trajectories fell entirely within the lower or upper visual field. Reaction times were faster for more natural shapes and orientations, regardless of visual field. Overall accuracy was poorer and movement time was longer for the inverted tent condition than the other three conditions, perhaps because it was imperfectly reminiscent of a bouncing ball. A detailed analysis of spatial errors revealed that interception endpoints were more likely to fall along the path of the final trajectory in upright vs. inverted conditions, suggesting stronger expectations regarding the final trajectory direction for these conditions. Taken together, these results suggest that the naturalness of the shape and orientation of a trajectory contributes to performance in a virtual interception task.

Evoked Potentials to the Movement of Sound Stimuli with Interaural Intensity Differences

Evoked Potentials to the Movement of Sound Stimuli with Interaural Intensity Differences

Correlation Analysis Approach Between Features and Motor Movement Stimulus for Stroke Severity Classification of EEG Signal Based on Time Domain, Frequency Domain, and Signal Decomposition Domain

The healing process of a stroke necessitates tools for measuring relevant parameters to facilitate monitoring, evaluation, and medical rehabilitation. Accurate parameter measures can be observed in stroke patients' severity to ascertain suitable interventions by identifying components pertinent to monitoring, evaluation, and medical rehabilitation. The components are derived from the observation collection process utilizing an EEG device, accompanied by a motor stimulus, to ensure the acquisition of EEG signals for monitoring, evaluation, and medical rehabilitation while preventing any loss of information during data collection. The acquired information encounters challenges due to the signal's unstable, nonlinear, and non-stationary characteristics, necessitating efforts to stabilize, render stationary, and linearize it through suitable signal processing and feature extraction techniques to achieve a pertinent feature composition. The subsequent difficulty is achieving the objectives of medical monitoring, evaluation, and rehabilitation, necessitating the correlation between EEG signal characteristics and motor movement stimuli, ensuring that the process adheres to appropriate parameter identification and scheduling per the established plan. In response to this difficulty, a correlation analysis methodology is established, incorporating normalcy tests, significance tests, and correlation analysis to ensure that the relevant factors for identifying stroke severity categorization patterns are precisely identified beforehand. The correlation analysis strategy employs raw data situations, preprocessing, feature extraction, feature selection, and correlation analysis for classification purposes. Our experimental findings indicate that the correlation analysis approach for assessing stroke severity classification patterns is evident in the Hajorth Complexity feature, utilizing the Shoulder motor movement stimulus and the SVM classification type, achieving an accuracy significant value of 98%. These findings confirm the efficacy of correlation analysis between EEG signal features and motor movement stimuli in identifying the optimal parameters within a reduced dimensional space to assess stroke severity effectively.

A paradoxical misperception of relative motion

Detecting the motion of an object relative to a world-fixed frame of reference is an exquisite human capability [G. E. Legge, F. Campbell, Vis. Res. 21, 205-213 (1981)]. However, there is a special condition where humans are unable to accurately detect relative motion: Images moving in a direction consistent with retinal slip where the motion is unnaturally amplified can, under some conditions, appear stable [D. W. Arathorn, S. B. Stevenson, Q. Yang, P. Tiruveedhula, A. Roorda, J. Vis. 13, 22 (2013)]. We asked: Is world-fixed retinal image background content necessary for the visual system to compute the direction of eye motion, and consequently generate stable percepts of images moving with amplified slip? Or, are nonvisual cues sufficient? Subjects adjusted the parameters of a stimulus moving in a random trajectory to match the perceived motion of images moving contingent to the retina. Experiments were done with and without retinal image background content. The perceived motion of stimuli moving with amplified retinal slip was suppressed in the presence of a visible background; however, higher magnitudes of motion were perceived under conditions when there was none. Our results demonstrate that the presence of retinal image background content is essential for the visual system to compute its direction of motion. The visual content that might be thought to provide a strong frame of reference to detect amplified retinal slips, instead paradoxically drives the misperception of relative motion.

Visual Upward/Downward Motion Elicits Fast and Fluent High-/Low-Pitched Speech Production

Abstract Participants tend to produce a higher or lower vocal pitch in response to upward or downward visual motion, suggesting a pitch–motion correspondence between the visual and speech production processes. However, previous studies were contaminated by factors such as the meaning of vocalized words and the intrinsic pitch or tongue movements associated with the vowels. To address these issues, we examined the pitch–motion correspondence between simple visual motion and pitched speech production. Participants were required to produce a high- or low-pitched meaningless single vowel [a] in response to the upward or downward direction of a visual motion stimulus. Using a single vowel, we eliminated the artifacts related to the meaning, intrinsic pitch, and tongue movements of multiple vocalized vowels. The results revealed that vocal responses were faster when the pitch corresponded to the visual motion (consistent condition) than when it did not (inconsistent condition). This result indicates that the pitch–motion correspondence in speech production does not depend on the stimulus meaning, intrinsic pitch, or tongue movement of the vocalized words. In other words, the present study suggests that the pitch–motion correspondence can be explained more parsimoniously as an association between simple sensory (visual motion) and motoric (vocal pitch) features. Additionally, acoustic analysis revealed that speech production aligned with visual motion exhibited lower stress, greater confidence, and higher vocal fluency.

Different effects of smooth pursuit eye movements on motion-based stimulus response congruency.

In the motion-based stimulus-response compatibility (SRC) effect, responses are faster when the task-irrelevant stimulus motion is congruent with the response movement performance. In the present study, we tested whether smooth pursuit eye movements, related to tracking a moving object, influence motion-based SRC when present on their own or when combined with position-based SRC. We examined the motion-based SRC effect during both the response selection and response execution stages. When investigating motion-based SRC alone, participants responded with left or right movements of the single hand to the left or right movements of a centrally presented stimulus, either with their eyes fixated at the center or tracking the moving object. In the case of combined motion-based and position-based SRC, participants responded with left or right movements of the left or right hand to stimulus motion presented on the left or right side of the screen, again with eyes either fixated at the center or following the moving target. Results showed that during the response selection stage, smooth pursuit type eye movements had no effect on the motion-based SRC when the stimulus moved in the center, whereas the effect was enhanced when the stimulus presentation was lateralized. This aligns with the idea that attentional shifts differ between central and peripheral vision and that cognitive system computes various spatial maps for stimulus and response. In the case of response execution, smooth pursuit type eye movements had no effect on the motion-based SRC effect, regardless of stimulus location.

Inability to pursue nonrigid motion produces instability of spatial perception.

Vision generates a stable representation of space by combining retinal input with internal predictions about the visual consequences of eye movements. We report a type of nonrigid motion that disrupts the connection between eye movements and perception, causing visual instability. This motion is accurately perceived during fixation, but it cannot be pursued. Catch-up saccades are accurately directed to the moving target but the motion stimulus appears to jump in space with each saccade. Our results reveal four major findings about perception and the visuomotor system: (i) Pursuit fails for certain types of motion; (ii) pursuit and catch-up saccades are independently controlled; (iii) prediction of saccade consequences is independent from saccade control; and (iv) the visual stability of moving objects relies on similar motion mechanisms as pursuit.

When sounds come alive: animacy in the auditory sense.

Despite the interest in animacy perception, few studies have considered sensory modalities other than vision. However, even everyday experience suggests that the auditory sense can also contribute to the recognition of animate beings, for example through the identification of voice-like sounds or through the perception of sounds that are the by-products of locomotion. Here we review the studies that have investigated the responses of humans and other animals to different acoustic features that may indicate the presence of a living entity, with particular attention to the neurophysiological mechanisms underlying such perception. Specifically, we have identified three different auditory animacy cues in the existing literature, namely voicelikeness, consonance, and acoustic motion. While the first two characteristics are clearly exclusive to the auditory sense and indicate the presence of an animate being capable of producing vocalizations or harmonic sounds-with the adaptive value of consonance also being exploited in musical compositions in which the musician wants to convey certain meanings-acoustic movement is, on the other hand, closely linked to the perception of animacy in the visual sense, in particular to self-propelled and biological motion stimuli. The results presented here support the existence of a multifaceted auditory sense of animacy that is shared by different distantly related species and probably represents an innate predisposition, and also suggest that the mechanisms underlying the perception of living things may all be part of an integrated network involving different sensory modalities.

Time courses of brain plasticity underpinning visual motion perceptual learning

Visual perceptual learning (VPL) refers to a long-term improvement of visual task performance through training or experience, reflecting brain plasticity even in adults. In human subjects, VPL has been mostly studied using functional magnetic resonance imaging (fMRI). However, due to the low temporal resolution of fMRI, how VPL affects the time course of visual information processing is largely unknown. To address this issue, we trained human subjects to perform a visual motion direction discrimination task. Their behavioral performance and magnetoencephalography (MEG) signals responding to the motion stimuli were measured before, immediately after, and two weeks after training. Training induced a long-lasting behavioral improvement for the trained direction. Based on the MEG signals from occipital sensors, we found that, for the trained motion direction, VPL increased the motion direction decoding accuracy, reduced the motion direction decoding latency, enhanced the direction-selective channel response, and narrowed the tuning profile. Following the MEG source reconstruction, we showed that VPL enhanced the cortical response in early visual cortex (EVC) and strengthened the feedforward connection from EVC to V3A. These VPL-induced neural changes co-occurred in 160–230 ms after stimulus onset. Complementary to previous fMRI findings on VPL, this study provides a comprehensive description on the neural mechanisms of visual motion perceptual learning from a temporal perspective and reveals how VPL shapes the time course of visual motion processing in the adult human brain.

Direct observation of the neural computations underlying a single decision

Neurobiological investigations of perceptual decision-making have furnished the first glimpse of a flexible cognitive process at the level of single neurons. Neurons in the parietal and prefrontal cortex are thought to represent the accumulation of noisy evidence, acquired over time, leading to a decision. Neural recordings averaged over many decisions have provided support for the deterministic rise in activity to a termination bound. Critically, it is the unobserved stochastic component that is thought to confer variability in both choice and decision time. Here, we elucidate this drift-diffusion signal on individual decisions. We recorded simultaneously from hundreds of neurons in the lateral intraparietal cortex of monkeys while they made decisions about the direction of random dot motion. We show that a single scalar quantity, derived from the weighted sum of the population activity, represents a combination of deterministic drift and stochastic diffusion. Moreover, we provide direct support for the hypothesis that this drift-diffusion signal approximates the quantity responsible for the variability in choice and reaction times. The population-derived signals rely on a small subset of neurons with response fields that overlap the choice targets. These neurons represent the integral of noisy evidence. Another subset of direction-selective neurons with response fields that overlap the motion stimulus appear to represent the integrand. This parsimonious architecture would escape detection by state-space analyses, absent a clear hypothesis.

Direct observation of the neural computations underlying a single decision.

Neurobiological investigations of perceptual decision-making have furnished the first glimpse of a flexible cognitive process at the level of single neurons. Neurons in the parietal and prefrontal cortex are thought to represent the accumulation of noisy evidence, acquired over time, leading to a decision. Neural recordings averaged over many decisions have provided support for the deterministic rise in activity to a termination bound. Critically, it is the unobserved stochastic component that is thought to confer variability in both choice and decision time. Here, we elucidate this drift-diffusion signal on individual decisions. We recorded simultaneously from hundreds of neurons in the lateral intraparietal cortex of monkeys while they made decisions about the direction of random dot motion. We show that a single scalar quantity, derived from the weighted sum of the population activity, represents a combination of deterministic drift and stochastic diffusion. Moreover, we provide direct support for the hypothesis that this drift-diffusion signal approximates the quantity responsible for the variability in choice and reaction times. The population-derived signals rely on a small subset of neurons with response fields that overlap the choice targets. These neurons represent the integral of noisy evidence. Another subset of direction-selective neurons with response fields that overlap the motion stimulus appear to represent the integrand. This parsimonious architecture would escape detection by state-space analyses, absent a clear hypothesis.

Use of anti-motion sickness reading glasses in vehicles: study protocol for a cluster-randomised trial

Motion sickness, or kinetosis, is a common phenomenon and is usually induced during passive locomotion in vehicles, generated by different body accelerations when movement stimuli occur. Its main symptoms are nausea, vomiting, paleness, and sweating in the exposed individual. Thus, the anti-motion sickness glasses were developed, which work using a fluid that moves in rings arranged around the eyes. This study protocol aims to evaluate the possibility that these glasses can avoid the sensory conflict that causes motion sickness, attenuating or eliminating the symptoms of motion sickness while reading in vehicles. Therefore, a crossover study shall be conducted, in which volunteers in two groups will travel in a standard car using antikinetosis goggles while reading, covering a predetermined path, in a trajectory that will last for 15 minutes. The first group (G1) will use functional glasses on the first day of testing. The second group (G2), in turn, will start the tests using the adulterated glasses, similar to the functional ones in appearance, but without the proposed effects of reducing or eliminating symptoms. On the second day of testing, for each group, the previously unused model will be employed instead. At the end of each clinical trial day, a questionnaire based in the MSSQ-Short shall be applied, evaluating the intensity of possible symptoms, their duration and the time till their appearance. Thus, the persistence of symptoms or the appearance of some clinical improvement will be evaluated, making it possible to verify the effectiveness of the object of study.

Evaluating the Effects of Motion Cues in Virtual Truck Driver Training

The integration of simulation technology into professional training has transformed learning in various sectors. Although prior research has explored motion cueing in simulators such as aviation training, driver navigation and performance, there is limited investigation into the impact of motion stimuli in VR-based truck driver training. This study investigates the driving performance of truck drivers in two virtual driving tasks, comparing conditions with and without motion cues. Participants wore virtual reality headsets and were situated within an immersive motion simulator. They completed two driving tasks involving truck docking and highway driving. Simulator sickness, stress, and user experience were assessed using the simulator sickness questionnaire, subjective unit of distress scale, and user experience questionnaire, respectively. Our findings suggest that motion cues hold potential to enhance subjective experiences, making driving more engaging, stimulating, and mitigating motion sickness. However, they did not significantly affect overall driving performance, except for steering behavior. Participants exhibited more engaged steering during highway driving when motion cues were present. Our findings suggest that the impact of motion cues is task-dependent, with their absence not showing a significant detrimental effect on driving performance in the simulated environment. Further validation with field-observed data is necessary to confirm these findings. These insights can guide future policies and regulations governing virtual truck driver training, ultimately ensuring improved safety and performance in the industry.

Moving spiders do not boost visual search in spider fear

Previous research on attention to fear-relevant stimuli has largely focused on static pictures or drawings, and thus did not consider the potential effect of natural motion. Here, we aimed to investigate the effect of motion on attentional capture in spider-fearful and non-fearful participants by using point-light stimuli and naturalistic videos. Point-light stimuli consist of moving dots representing joints and thereby visualizing biological motion (e.g. of a walking human or cat) without needing a visible body. Spider-fearful (n = 30) and non-spider-fearful (n = 31) participants completed a visual search task with moving targets (point-light/naturalistic videos) and static distractors (images), static targets and moving distractors, or static targets and static distractors. Participants searched for a specified animal type (snakes, spiders, cats, or doves) as quickly as possible. We replicated previous findings with static stimuli: snakes were detected faster and increased distraction, while spiders just increased distraction. However, contrary to our hypotheses, spider targets did not speed up responses, neither in the group of control nor in the group of spider-fearful participants. Interestingly, stimuli-specific effects were toned down, abolished, or even changed direction when motion was introduced. Also, we demonstrated that point-light stimuli were of similar efficiency as naturalistic videos, indicating that for testing effects of motion in visual search, “pure” motion stimuli might be sufficient. As we do show a substantial modulation of visual search phenomena by biological motion, we advocate for future studies to use moving stimuli, equivalent to our dynamic environment, to increase ecological validity.

Clinically established early Parkinson's disease patients do not show impaired use of priors in conditions of perceptual uncertainty

The ability to use past learned experiences to guide decisions is an important component of adaptive behavior, especially when decision-making is performed under time pressure or when perceptual information is unreliable. Previous studies using visual discrimination tasks have shown that this prior-informed decision-making ability is impaired in Parkinson's disease (PD), but the mechanisms underlying this deficit and the precise impact of dopaminergic denervation within cortico-basal circuits remain unclear. To shed light on this problem, we evaluated prior-informed decision-making under various conditions of perceptual uncertainty in a sample of 13 clinically established early PD patients, and compared behavioral performance with healthy control (HC) subjects matched in age, sex and education. PD patients and HC subjects performed a random dot motion task in which they had to decide the net direction (leftward vs. rightward) of a field of moving dots and communicate their choices through manual button presses. We manipulated prior knowledge by modulating the probability of occurrence of leftward vs. rightward motion stimuli between blocks of trials, and by explicitly giving these probabilities to subjects at the beginning of each block. We further manipulated stimulus discriminability by varying the proportion of dots moving coherently in the signal direction and speed-accuracy instructions. PD patients used choice probabilities to guide perceptual decisions in both speed and accuracy conditions, and their performance did not significantly differ from that of HC subjects. An additional analysis of the data with the diffusion decision model confirmed this conclusion. These results suggest that the impaired use of priors during visual discrimination observed at more advanced stages of PD is independent of dopaminergic denervation, though additional studies with larger sample sizes are needed to more firmly establish this conclusion.

Hue and orientation pinwheels in macaque area V4.

Area V4 is an intermediate-level area of the macaque visual cortical hierarchy that serves key functions in visual processing by integrating inputs from lower areas such as V1 and V2 and providing feedforward inputs to many higher cortical areas. Previous V4 imaging studies have focused on differential responses to color, orientation, disparity, and motion stimuli, but many details of the spatial organization of significant hue and orientation tuning have not been fully described. We used support vector machine (SVM) decoding of intrinsic cortical single-condition responses to generate high-resolution maps of hue and orientation tuning and to describe the organization of hue and orientation pinwheels in V4. Like V1 and V2, V4 contains maps of orientation that are organized as pinwheels. V4 also contains maps of hue that are organized as pinwheels, whose circular organization more closely represents the perception of hue than is observed in antecedent cortical areas. Unlike V1, where orientation is continuously mapped across the surface, V4 hue and orientation pinwheels are organized in limited numbers of pinwheel sequences. The organization of these sequences and the distance between pinwheels may provide insight into the functional organization of V4. Regions significantly tuned for hue occupy roughly four times that of the orientation, are largely separated from each other, and overlap by roughly 5%. This spatial organization is largely consistent with segregated inputs arising from V2 thin and interstripes. This modular organization of V4 suggests that further integration of color and shape might occur in higher areas in inferotemporal cortical.NEW & NOTEWORTHY The representation of hue and orientation in macaque monkey area V4 was determined by intrinsic cortical imaging of responses to isoluminant hues and achromatic grating stimuli. Vector summation of support vector machine (SVM) decoded single-condition responses was used to generate hue and orientation maps that, like V1 orientation maps, were both characterized by distinct pinwheel patterns. These data suggest that pinwheels are an important structure to represent different stimulus features across multiple visual cortical areas.

Weighted power summation and contrast normalization mechanisms account for short-latency eye movements to motion and disparity of sine-wave gratings and broadband visual stimuli in humans.

In this paper, we show that the model we proposed earlier to account for the disparity vergence eye movements (disparity vergence responses, or DVRs) in response to horizontal and vertical disparity steps of white noise visual stimuli also provides an excellent description of the short-latency ocular following responses (OFRs) to broadband stimuli in the visual motion domain. In addition, we reanalyzed the data and applied the model to several earlier studies that used sine-wave gratings (single or a combination of two or three gratings) and white noise stimuli. The model provides a very good account of all of these data. The model postulates that the short-latency eye movements-OFRs and DVRs-can be accounted for by the operation of two factors: an excitatory drive, determined by a weighted sum of contributions of stimulus Fourier components, scaled by a global contrast normalization mechanism. The output of the operation of these two factors is then nonlinearly scaled by the total contrast of the stimulus. Despite different roles of disparity (horizontal and vertical) and motion signals in visual scene analyses, the earliest processing stages of these different signals appear to be very similar.