Motion Stimuli Research Articles

Visual Neurophysiological Biomarkers for Patient Stratification and Treatment Development Across Neuropsychiatric Disorders.

The human visual system begins in the retina and projects to cortex through both the thalamocortical and retinotectal visual pathways. The thalamocortical system is divided into separate magnocellular and parvocellular divisions, which engage separate layers of the lateral geniculate nucleus (LGN) and project preferentially to the dorsal and ventral visual streams, respectively. The retinotectal system, in contrast, projects to the superior colliculus, pulvinar nucleus of the thalamus and amygdala. The pulvinar nucleus also plays a critical role in the integration of information processing across early visual regions.The functions of the visual system can be assessed using convergent EEG- and functional brain imaging approaches, increasingly supplemented by simultaneously collected eye-tracking information. These approaches may be used for tracing the flow of information from retina through early visual regions, as well as the contribution of these regions to higher-order cognitive processing. A pathway of increasing interest in relationship to neuropsychiatric disorders is the primate-specific "third visual pathway" that relies extensively on motion-related input and contributes preferentially to social information processing. Thus, disturbances in the brain's responsiveness to motion stimuli may be especially useful as biomarkers for early visual dysfunction related to impaired social cognition.Visual event-related potentials (ERPs) can be collected with high-fidelity and have proven effective for the study of neuropsychiatric disorders such as schizophrenia and Alzheimer's disease, in which alterations in visual processing may occur early in the disorder, andautism-spectrum disorder (ASD), in which abnormal persistence of early childhood patterns may persist into adulthood, leading to impaired functioning of visual social pathways. The utility of visual ERPs as biomarkers for larger clinical studies is limited at present by the need for standardization of visual stimuli across laboratories, which requires specialized protocols and equipment. The development of optimized stimulation protocols as well as newer headset-based systems may increase the clinical utility of present stimulation approaches.

Incongruent active head rotations increase visual motion detection thresholds.

Attributing a visual motion signal to its correct source-be that external object motion, self-motion, or some combination of both-seems effortless, and yet often involves disentangling a complex web of motion signals. Existing literature focuses on either translational motion (heading) or eye movements, leaving much to be learnt about the influence of a wider range of self-motions, such as active head rotations, on visual motion perception. This study investigated how active head rotations affect visual motion detection thresholds, comparing conditions where visual motion and head-turn direction were either congruent or incongruent. Participants judged the direction of a visual motion stimulus while rotating their head or remaining stationary, using a fixation-locked Virtual Reality display with integrated head-movement recordings. Thresholds to perceive visual motion were higher in both active-head rotation conditions compared to stationary, though no differences were found between congruent or incongruent conditions. Participants also showed a significant bias to report seeing visual motion travelling in the same direction as the head rotation. Together, these results demonstrate active head rotations increase visual motion perceptual thresholds, particularly in cases of incongruent visual and active vestibular stimulation.

The effect of rhythmic stimuli with spatial information on sensorimotor synchronization: an EEG and EMG study.

Sensorimotor synchronization (SMS) is the human ability to align body movement rhythms with external rhythmic stimuli. While the effects of rhythmic stimuli containing only temporal information on SMS have been extensively studied, less is known about how spatial information affects SMS performance. This study investigates the neural mechanisms underlying SMS with rhythmic stimuli that include both temporal and spatial information, providing insights into the influence of these factors across different sensory modalities. This study compared the effects temporal information and spatial information on SMS performance across different stimuli conditions. We simultaneously recorded the electroencephalogram (EEG), the electromyogram (EMG), and behavioral data as subjects performed synchronized tapping to rhythmic stimuli. The study analyzed SMS performance under conditions including auditory, visual, and auditory-visual motion stimuli (containing both temporal and spatial information), as well as auditory, visual, and auditory-visual non-motion stimuli (containing only temporal information). Specifically, the research examined behavioral data (i.e., mean asynchrony, absolute asynchrony, and variability), neural oscillations, cortico-muscular coherence (CMC), and brain connectivity. The results demonstrated that SMS performance was superior with rhythmic stimuli containing both temporal and spatial information compared to stimuli with only temporal information. Moreover, sensory-motor neural entrainment was stronger during SMS with rhythmic stimuli containing spatial information within the same sensory modality. SMS with both types of rhythmic stimuli was found to be dynamically modulated by neural oscillations and cortical-muscular coupling in the beta band (13-30 Hz). These findings provide deeper insights into the combined effects of temporal and spatial information, as well as sensory modality, on SMS performance. The study highlights the dynamic modulation of SMS by neural oscillations and CMC, particularly in the beta band, offering valuable contributions to understanding the neural basis of sensorimotor synchronization.

Automatic imitation in children: Age-related change and comparison to adults.

Automatic imitation, in which one person's movement is affected by the observation of another person's movements, has been widely reported. However, it remains unclear how automatic imitation changes over a wide age range, particularly during childhood. In this study, we examined the differences in the tendency for automatic imitation between adults and children and the cross-sectional age-related changes in children aged 5-12 years, using a stimulus-response conflict paradigm. In this task, participants perform a choice-reactive finger movement corresponding to a given response stimulus while observing another participant's compatible or incompatible movement stimuli. The tendency for automatic imitation was assessed based on the reaction time, correct rate, and inverse efficiency score. The results showed that the degree of automatic imitation was weak until the children were 7 years old. Interestingly, our results show that the tendency for automatic imitation during childhood changed to an inverted U-shape, indicating nonlinear changes in automatic imitation during childhood. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Head-centric computing for vestibular stimulation under head-free conditions.

Background: The vestibular end organs (semicircular canals, saccule and utricle) monitor head orientation and motion. Vestibular stimulation by means of controlled translations, rotations or tilts of the head represents a routine manoeuvre to test the vestibular apparatus in a laboratory or clinical setting. In diagnostics, it is used to assess oculomotor postural or perceptual responses, whose abnormalities can reveal subclinical vestibular dysfunctions due to pathology, aging or drugs. Objective: The assessment of the vestibular function requires the alignment of the motion stimuli as close as possible with reference axes of the head, for instance the cardinal axes naso-occipital, interaural, cranio-caudal. This is often achieved by using a head restraint, such as a helmet or strap holding the head tightly in a predefined posture that guarantees the alignment described above. However, such restraints may be quite uncomfortable, especially for elderly or claustrophobic patients. Moreover, it might be desirable to test the vestibular function under the more natural conditions in which the head is free to move, as when subjects are tracking a visual target or they are standing erect on the moving platform. Here, we document algorithms that allow delivering motion stimuli aligned with head-fixed axes under head-free conditions. Methods: We implemented and validated these algorithms using a MOOG-6DOF motion platform in two different conditions. 1) The participant kept the head in a resting, fully unrestrained posture, while inter-aural, naso-occipital or cranio-caudal translations were applied. 2) The participant moved the head continuously while a naso-occipital translation was applied. Head and platform motion were monitored in real-time using Vicon. Results: The results for both conditions showed excellent agreement between the theoretical spatio-temporal profile of the motion stimuli and the corresponding profile of actual motion as measured in real-time. Conclusion: We propose our approach as a safe, non-intrusive method to test the vestibular system under the natural head-free conditions required by the experiential perspective of the patients.

Mapping the avian visual tectofugal pathway using 3D reconstruction.

Image processing in amniotes is usually accomplished by the thalamofugal and/or tectofugal visual systems. In laterally eyed birds, the tectofugal system dominates with functions such as color and motion processing, spatial orientation, stimulus identification, and localization. This makes it a critical system for complex avian behavior. Here, the brains of chicks, Gallus gallus, were used to produce serial brain sections in either coronal, sagittal, or horizontal planes and stained with either Nissl and Gallyas silver myelin or Luxol fast blue stain and cresyl echt violet (CEV). The emerging techniques of diffusible iodine-based contrast-enhanced computed tomography (diceCT) coupled with serial histochemistry in three planes were used to generate a comprehensive three-dimensional (3D) model of the avian tectofugal visual system. This enabled the 3D reconstruction of tectofugal circuits, including the three primary neuronal projections. Specifically, major components of the system included four regions of the retina, layers of the optic tectum, subdivisions of the nucleus rotundus in the thalamus, the entopallium in the forebrain, and supplementary components connecting into or out of this major avian visual sensory system. The resulting 3D model enabled a better understanding of the structural components and connectivity of this complex system by providing a complete spatial organization that occupied several distinct brain regions. We demonstrate how pairing diceCT with traditional histochemistry is an effective means to improve the understanding of, and thereby should generate insights into, anatomical and functional properties of complicated neural pathways, and we recommend this approach to clarify enigmatic properties of these pathways.

Pre-saccadic Neural Enhancements in Marmoset Area MT.

Each time we make an eye movement, attention moves before the eyes, resulting in a perceptual enhancement at the target. Recent psychophysical studies suggest that this pre-saccadic attention enhances the visual features at the saccade target, whereas covert attention causes only spatially selective enhancements. While previous nonhuman primate studies have found that pre-saccadic attention does enhance neural responses spatially, no studies have tested whether changes in neural tuning reflect an automatic feature enhancement. Here we examined pre-saccadic attention using a saccade foraging task developed for marmoset monkeys (one male and one female). We recorded from neurons in the middle temporal area with peripheral receptive fields that contained a motion stimulus, which would either be the target of a saccade or a distracter as a saccade was made to another location. We established that marmosets, like macaques, show enhanced pre-saccadic neural responses for saccades toward the receptive field, including increases in firing rate and motion information. We then examined if the specific changes in neural tuning might support feature enhancements for the target. Neurons exhibited diverse changes in tuning but predominantly showed additive and multiplicative increases that were uniformly applied across motion directions. These findings confirm that marmoset monkeys, like macaques, exhibit pre-saccadic neural enhancements during saccade foraging tasks with minimal training requirements. However, at the level of individual neurons, the lack of feature-tuned enhancements is similar to neural effects reported during covert spatial attention.

Poster Session II: Computational analysis of the effect of cone temporal filtering on detection threshold with and without retinal motion.

Retinal stimulus motion can increase visual acuity, but recent experimental evidence indicates that for briefly presented stimuli this benefit does not always occur (Braun et al, VSS 2023). To understand this effect, we modeled how the temporally low-pass filtering that occurs within each cone is expected to impact visual performance. We simulated a grating (10 cpd Gabor) detection task in which the stimulus was present for two 15 msec frames. We used the ISETBio software to compute cone excitations and cone photocurrent responses to the stimulus, for different contrasts and retinal positions, and used linear SVM classifiers to estimate computational-observer detection thresholds. We examined three retinal-motion conditions: 1) stimulus stabilized on the retina; 2) stimulus shifted 0.5 cycle orthogonal to grating orientation across the two frames; 3) stimulus shifted 1 cycle. Across all three conditions, detection threshold estimated on the basis of cone excitations varied little. Threshold estimated on the basis of photocurrent, however, was highest for the 0.5 cycle shift, and about the same for the no shift and 1 cycle shift conditions. Qualitatively, this result recapitulates the findings of Braun et al. and suggests that those findings may be understood as a consequence of the initial visual encoding. We note, however, that we analyzed detection rather than acuity; planned work will attempt to bring the computations into more direct contact with the experimental results.

Introspective inference counteracts perceptual distortion

Introspective agents can recognize the extent to which their internal perceptual experiences deviate from the actual states of the external world. This ability, also known as insight, is critically required for reality testing and is impaired in psychosis, yet little is known about its cognitive underpinnings. We develop a Bayesian modeling framework and a psychophysics paradigm to quantitatively characterize this type of insight while people experience a motion after-effect illusion. People can incorporate knowledge about the illusion into their decisions when judging the actual direction of a motion stimulus, compensating for the illusion (and often overcompensating). Furthermore, confidence, reaction-time, and pupil-dilation data all show signatures consistent with inferential adjustments in the Bayesian insight model. Our results suggest that people can question the veracity of what they see by making insightful inferences that incorporate introspective knowledge about internal distortions.

Seasickness susceptibility and the vestibular time constant: a prospective study.

Human passive motion during boat, car or airplane travel may trigger motion sickness. Seasickness is the most provoking manifestation of motion sickness. It imposes major constraints on quality of life and human performance. Based on seasickness susceptibility the population is usually categorized into susceptible (S) and non-susceptible (NS). During repeated exposure some susceptible individuals undergo habituation and obtain symptoms relief, reflecting a third group of habituating (H) individuals. Recently, accumulative evidence suggests that the vestibular time constant (Tc) is associated with motion sickness susceptibility and attenuation of symptoms. These studies demonstrated that repeated passive motion stimuli lead to temporary short-term (days) changes in Tc, whereas sea sickness habituation process lasts 3 to 6months. Therefore, the goal of the present study was to examine the behavior of Tc during the entire span of the seasickness habituation process between the H, S and NS groups to find an objective test for seasickness severity prediction. Tc of 30 subjects was prospectively evaluated pre, 3 and 6months post exposure to sea environment using a computerized rotatory chair system protocol. Seasickness severity was evaluated by Wiker questionnaire. Significantly shorter Tc was found in the S group compared with the NS and H groups. Further analysis revealed lower maximal Slow Phase Velocity (mSPV) and nystagmus frequency (total number of beats/second) in the S group. Our results suggest that Tc, mSPV and nystagmus frequency might serve as a prediction for seasickness severity. This study was retrospectively registered on December 7th 2022 and assigned the identifier number NCT05640258.

A new online paradigm to measure spontaneous pointing in infants and caregivers

Index-finger pointing is a milestone in the development of referential communication. Previous research has investigated infants’ pointing with a variety of paradigms ranging from parent reports to field observations to experimental settings, suggesting that lab-based semi-natural interactional settings seem especially suited to elicit and measure infant pointing. With the Covid-pandemic the need for a comparable online tool became evident enabling also efficient, low-cost, large-scale, diverse data collection. The current study introduces a remote online paradigm, based on the established live ‘decorated-room’ paradigm. In Experiment 1, 12-months old infants and their caregivers (N = 24) looked at digitally presented stimuli together while being recorded with their webcam. We coded pointing gestures of infants and caregivers as well as caregivers’ responses to infants’ pointing. In Experiment 2 (N = 47), we optimized stimuli and investigated influences of stimulus characteristics. We systematically varied the style of depiction, stimulus complexity, motion, and facial stimuli. Main findings were that infants and caregivers pointed spontaneously, with mean behaviors ranging within the benchmarks of previously reported findings of the live decorated-room paradigm. Further, the social setting was preserved as revealed by significant relations between parents’ responsive points and infants’ pointing frequency. Analyses of stimuli characteristics revealed that infants pointed more to stimuli depicting faces than to other stimuli. The new remote online paradigm proves a useful addition to established paradigms. It offers novel opportunities for simplified assessments, large-scale sampling, and worldwide, diversified data collection.

The effects of synchronous and asynchronous steady-state auditory-visual motion on EEG characteristics in healthy young adults

The brain’s integration of motion information from visual and auditory senses is essential for human to be able to duly respond to the dynamic living environment. Research on the impact of steady-state auditory motion and steady-state visual motion synchronous stimuli and minor asynchronous stimuli on electroencephalogram (EEG) is lacking. This study designed steady-state visual motion paradigms, steady-state auditory motion paradigms, steady-state auditory-visual synchronous motion paradigms, and steady-state auditory-visual asynchronous motion paradigms. Then the effects of steady-state auditory-visual motion stimuli on EEG were analyzed from the aspects of time domain, frequency domain, connectivity, and source localization. Our study showed that the synchronous steady-state auditory-visual motion stimuli and the asynchronous steady-state auditory-visual motion stimuli can enhance brain responses in a subadditive mode and significantly activated auditory and visual integration areas compared to single-modal visual and auditory stimuli. Moreover, asynchronous steady-state auditory-visual motion stimuli activated the Anterior Cingulate (ACG) compared to synchronous steady-state auditory-visual motion stimuli. Our study demonstrated that ACG regions were involved in conflicting processing of steady-state auditory-visual motion information. This study further enriches the cutting edge of auditory-visual motion integration.

Encoding of continuous perceptual choices in human early visual cortex.

Research on the neural mechanisms of perceptual decision-making has typically focused on simple categorical choices, say between two alternative motion directions. Studies on such discrete alternatives have often suggested that choices are encoded either in a motor-based or in an abstract, categorical format in regions beyond sensory cortex. In this study, we used motion stimuli that could vary anywhere between 0° and 360° to assess how the brain encodes choices for features that span the full sensory continuum. We employed a combination of neuroimaging and encoding models based on Gaussian process regression to assess how either stimuli or choices were encoded in brain responses. We found that single-voxel tuning patterns could be used to reconstruct the trial-by-trial physical direction of motion as well as the participants' continuous choices. Importantly, these continuous choice signals were primarily observed in early visual areas. The tuning properties in this region generalized between choice encoding and stimulus encoding, even for reports that reflected pure guessing. We found only little information related to the decision outcome in regions beyond visual cortex, such as parietal cortex, possibly because our task did not involve differential motor preparation. This could suggest that decisions for continuous stimuli take can place already in sensory brain regions, potentially using similar mechanisms to the sensory recruitment in visual working memory.

Neural processing of bottom-up perception of biological motion under attentional load

Considering its importance for one’s survival and social significance, biological motion (BM) perception is assumed to occur automatically. Previous behavioral results showed that task-irrelevant BM in the periphery interfered with task performance at the fovea. Under selective attention, BM perception is supported by a network of regions including the occipito-temporal (OTC), parietal, and premotor cortices. Retinotopy studies that use BM stimulus showed distinct maps for its processing under and away from selective attention. Based on these findings, we investigated how bottom-up perception of BM would be processed in the human brain under attentional load when it was shown away from the focus of attention as a task-irrelevant stimulus. Participants (N = 31) underwent an fMRI study in which they performed an attentionally demanding visual detection task at the fovea while intact or scrambled point light displays of BM were shown at the periphery. Our results showed the main effect of attentional load in fronto-parietal regions and both univariate activity maps and multivariate pattern analysis results support the attentional load modulation on the task-irrelevant peripheral stimuli. However, this effect was not specific to intact BM stimuli and was generalized to motion stimuli as evidenced by the motion-sensitive OTC involvement during the presence of dynamic stimuli in the periphery. These results confirm and extend previous work by showing that task-irrelevant distractors can be processed by stimulus-specific regions when there are enough attentional resources available. We discussed the implications of these results for future studies.

Analysis of Antennal Responses to Motion Stimuli in the Honey Bee by Automated Tracking Using DeepLabCut

Considering recent developments in gene manipulation methods for honey bees, establishing simple and robust assay systems which can analyze behavioral components in detail inside a laboratory is important for the rise of behavioral genetics in the honey bee. We focused on the antennal movements of the honey bee and developed an experimental system for analyzing the antennal responses (ARs) of the honey bee using DeepLabCut, a markerless posture-tracking tool using deep learning. The tracking of antennal movements using DeepLabCut during the presentation of vertical (downward and upward) motion stimuli successfully detected the direction-specific ARs in the transverse plane, which has been reported in the previous studies where bees tilted their antennae in the direction opposite to the motion stimuli. In addition, we found that honey bees also exhibited direction-specific ARs in the coronal plane in response to horizontal (forward and backward) motion stimuli. Furthermore, an investigation of the developmental maturation of honey bee ARs showed that ARs to motion stimuli were not detected in bees immediately after emergence but became detectable through post-emergence development in an experience-independent manner. Finally, unsupervised clustering analysis using multidimensional data created by processing tracking data using DeepLabCut classified antennal movements into different clusters, suggesting that data-driven behavioral classification can apply to AR paradigms. In summary, our results revealed direction-specific ARs even in the coronal plane to horizontal motion stimuli and developmental maturation of ARs for the first time, and suggest the efficacy of data-driven analysis for behavioral classification in behavioral studies of the honey bee.

The Effect of Stimulus Contrast and Spatial Position on Saccadic Eye Movement Parameters.

(1) Background: Saccadic eye movements are rapid eye movements aimed to position the object image on the central retina, ensuring high-resolution data sampling across the visual field. Although saccadic eye movements are studied extensively, different experimental settings applied across different studies have left an open question of whether and how stimulus parameters can affect the saccadic performance. The current study aims to explore the effect of stimulus contrast and spatial position on saccadic eye movement latency, peak velocity and accuracy measurements. (2) Methods: Saccadic eye movement targets of different contrast levels were presented at four different spatial positions. The eye movements were recorded with a Tobii Pro Fusion video-oculograph (250 Hz). (3) Results: The results demonstrate a significant effect of stimulus spatial position on the latency and peak velocity measurements at a medium grey background, 30 cd/m2 (negative and positive stimulus polarity), light grey background, 90 cd/m2 (negative polarity), and black background, 3 cd/m2 (positive polarity). A significant effect of the stimulus spatial position was observed on the accuracy measurements when the saccadic eye movement stimuli were presented on a medium grey background (negative polarity) and on a black background. No significant effect of stimulus contrast was observed on the peak velocity measurements under all conditions. A significant stimulus contrast effect on latency and accuracy was observed only on a light grey background. (4) Conclusions: The best saccadic eye movement performance (lowest latency, highest peak velocity and accuracy measurements) can be observed when the saccades are oriented to the right and left from the central fixation point. Furthermore, when presenting the stimulus on a light grey background, a very low contrast stimuli should be considered carefully.

Explicit effort may not influence perceptuomotor decision-making.

Many decisions that humans make are enacted by the action system. For example, humans use reach-to-grasp movements when making perceptuomotor decisions between and obtaining fruits of varying quality from a pile. Recent work suggests that the characteristics of each action alternative may influence the decision itself-there may be a bias away from making perceptuomotor alternatives associated with high effort when participants are unaware of the effort differences between responses. The present study examined if perceptuomotor decisions were influenced by explicit reaching effort differences. Neurotypical human participants were presented with random dot motion stimuli in which most dots moved in random directions and varying percentages of remaining dots moved coherently left- or rightward. Participants reported leftward motion judgements by performing leftward (or left hand) reaching movements and rightward motion judgements by performing rightward (or right hand) reaching movements. A resistance band was affixed to participants' wrists and to the table in different configurations. The configurations allowed for one movement/motion direction judgement to always require stretching of the band and, therefore, require relatively more effort. Across a set of experiments, the response context (i.e. selecting directions within a limb or selecting between limbs) and the effort difference between responses were manipulated. Overall, no experiment revealed a bias away from the perceptuomotor decision associated with high effort. Based on these results, it is concluded that, in this biomechanical context, explicit effort may not influence perceptuomotor decision-making and may point to a contextual influence of action effort on perceptuomotor decision-making.

Flickering stimuli presentation in imprinting

Imprinting, the process of forming lasting social bonds with early encountered stimuli, has been the subject of extensive research. However, there is still a need to systematically study the optimal methods for displaying imprinting stimuli in laboratory settings. This study aimed to investigate the effectiveness of different virtual presentation methods for imprinting stimuli and their impact on the memory of chicks. In the first experiment, we examined the attractiveness of various flickering frequencies, comparing them to static and translatory motion stimuli. The results revealed that flickering frequencies between 0.5 and 5 Hz were particularly appealing to newly hatched chicks, while higher frequencies (10–40 Hz) were less effective. We observed no significant differences in attractiveness between low flickering frequencies, moving stimuli, and static stimuli. In the second experiment, the focus shifted to the development of imprinting preference and memory. We found no significant difference in terms of preference for the imprinting stimulus between chicks imprinted with translatory motion or static stimuli. However, imprinting with flickering stimuli produced varied preferences. Chicks imprinted with a 2 Hz flickering stimulus exhibited a preference for the imprinting stimulus, albeit weaker than those imprinted with moving stimuli, while chicks imprinted with a 1 Hz flickering stimulus did not show a preference. These findings suggest that imprinting with flickering frequencies is not as effective as imprinting with moving stimuli and, to a lesser extent, static stimuli. Future studies should aim to determine the most optimal low frequencies within the 0.5–5 Hz range and explore different motion types. Overall, this research enhances our understanding of imprinting and provides valuable insights into virtual stimulation methods, thus informing the design of experiments in virtual environments.

An Illusory Motion in Stationary Stimuli Alters Their Perceived Duration.

Despite having equal duration, stimuli in physical motion are perceived to last longer than static ones. Here, we investigate whether illusory motion stimuli produce a time-dilation effect similar to physical motion. Participants performed a duration discrimination task that compared the perceived duration of static stimuli with and without illusory motion to a reference stimulus. In the first experiment, we observed a 4% increase in the number of "longer" responses for the illusory motion images than static stimuli with equal duration. The time-dilation effect, quantified as a shift in the Point of Subjective Equality (PSE), was approximately 55 ms for a 2-second stimulus. Although small, the effect was replicated in a second experiment in which the total number of standard-duration repetitions was reduced from 73 to 19. In the third experiment, we found a positive linear trend between the strength of the illusory motion and the magnitude of the time-dilation effect. These results demonstrate that, similar to physical motion stimuli, illusory motion stimuli are perceived to last longer than static stimuli. Furthermore, the strength of the illusion influences the extent of the lengthening of perceived duration.

Direct comparison reveals algorithmic similarities in fly and mouse visual motion detection

Evolution has equipped vertebrates and invertebrates with neural circuits that selectively encode visual motion. While similarities in the computations performed by these circuits in mouse and fruit fly have been noted, direct experimental comparisons have been lacking. Because molecular mechanisms and neuronal morphology in the two species are distinct, we directly compared motion encoding in these two species at the algorithmic level, using matched stimuli and focusing on a pair of analogous neurons, the mouse ON starburst amacrine cell (ON SAC) and Drosophila T4 neurons. We find that the cells share similar spatiotemporal receptive field structures, sensitivity to spatiotemporal correlations, and tuning to sinusoidal drifting gratings, but differ in their responses to apparent motion stimuli. Both neuron types showed a response to summed sinusoids that deviates from models for motion processing in these cells, underscoring the similarities in their processing and identifying response features that remain to be explained.