Eye Movements Research Articles

Time-Dependent Regulation of Sleep-Wakefulness and Electroencephalographic Characteristics by Spontaneous Running in Male Mice.

The relationship between physical activity and sleep quality is a critical area of investigation, given the importance of both behaviours for health and disease. Despite the common use of running wheels to assess circadian rhythms and exercise, their impact on sleep has not been thoroughly explored. Here, we present a detailed analysis of how voluntary running affected sleep/wakefulness duration, architecture and electrophysiological characteristics in mice. Sequential electroencephalogram (EEG) assessments revealed that voluntary running elicits a progressive alteration in sleep/wake configurations, including a reduction in overall daily sleep time and an enhancement in sleep/wakefulness consolidation. These modifications exhibited a temporal association with the intensity of running activities. The observed changes in sleep/wakefulness duration and architecture partially persist even after the discontinuation of running. Spontaneous running also gradually changed the amplitude and/or frequency of EEG theta power not only during the running phase but also in rapid eye movement sleep (REMS). Invivo endoscopic calcium imaging in freely behaving mice revealed that running and REMS were accompanied by the activation of largely shared yet distinctive neuronal cohorts within the hippocampal CA1 region, concomitant with EEG theta oscillations during both behaviours. These findings highlight the dynamic nature of sleep/wakefulness regulation in response to voluntary exercise and suggest that physical activity played a pivotal role in modulating sleep need and the daily balance between sleep and wakefulness.

A preparatory cranial potential for saccadic eye movements in macaque monkeys.

Response preparation is accomplished by gradual accumulation in neural activity until a threshold is reached. In humans, such a preparatory signal, referred to as the lateralized readiness potential, can be observed in the EEG over sensorimotor cortical areas before execution of a voluntary movement. Although well-described for manual movements, less is known about preparatory EEG potentials for saccadic eye movements in humans and nonhuman primates. Hence, we describe a lateralized readiness potential over the frontolateral cortex in macaque monkeys. Homologous to humans, we observed lateralized electrical potentials ramping before the execution of both rewarded and non-rewarded contralateral saccades. This potential parallels the neural spiking of saccadic movement neurons in the frontal eye field, suggesting that it may offer a non-invasive correlate of intracortical spiking activity. However, unlike neural spiking in the frontal eye field, polarization in frontolateral channels did not distinguish between saccade generation and inhibition. These findings provide new insights into non-invasive electrophysiological signatures of saccadic preparation in nonhuman primates, highlighting the potential of EEG measures to bridge invasive neural recordings and non-invasive studies of eye movement control in humans.Significance statement Exploring the neural processes that underpin movement preparation is central to linking brain activity with motor behavior. This study describes a lateralized readiness potential for saccades observed over the frontolateral cortex of macaque monkeys, analogous to human EEG signals previously observed during movement preparation. These observations set the foundation for future work to understand the neural generators of the lateralized readiness potential and offers a non-invasive tool to explore eye movement control. These insights could inform clinical and technological applications involving eye movement monitoring and control.

Climate warming may undermine sleep duration and quality in repeated-measure study of 23 million records

The impact of rising ambient temperatures on sleep and its phases under climate change is becoming increasingly concerning but remains underexplored. Sleep, consisting of non-rapid eye movement and rapid eye movement phases, is crucial for health, and insufficient sleep in either phase could have significant implications. Based on sleep monitoring data of 23 million days from 214,445 participants across mainland China, we investigated how daily average temperature affected sleep. For each 10 °C increase in ambient temperature, the odds of sleep insufficiency increased by 20.1%, while total sleep duration decreased by 9.67 minutes, with deep sleep declining the most (by 2.82%). Projections under the unrestricted (SSP5-8.5) greenhouse gas emission scenario suggest that by the end of the century, sleep insufficiency could rise by 10.50%, with an annual loss of 33.28 hours of sleep per person. These findings highlight the potential of climate warming to exacerbate sleep deprivation and degrade sleep quality, especially for the elderly, women, individuals with obesity, and regions of South, Centre and East.

Effect of hit rate and cognitive style on Bayesian reasoning: evidence from eye movements

Effect of hit rate and cognitive style on Bayesian reasoning: evidence from eye movements

Recent, but not long-term, priors induce behavioral oscillations in peri-saccadic vision

Perception of a continuous world relies on our ability to integrate discontinuous sensory signals when we make saccadic eye movements, which abruptly change the retinal image. Here we investigate the role of oscillations in integrating pre-saccadic information with the current sensory signals. We presented to participants (N = 24) a brief pre-saccadic Gabor stimulus (termed the inducer) before voluntary 16° saccades, followed by a test Gabor stimulus at various times before or after saccadic onset. Orientation judgments of the test stimulus were biased towards the orientation of both the inducer and previous (1-back) test stimulus, consistent with serial dependence. In addition to the average bias, judgments oscillated in synchrony with saccadic onset at alpha frequencies (~9.5 Hz) towards the orientation of the inducer or 1-back stimulus. There was also a strong bias towards the mean orientation (central tendency): however, that bias was constant over time, not associated with saccade-synched oscillations. Perceptual oscillations in serial dependence (but not central tendency) suggest that alpha rhythms may be instrumental in communicating short-term (but not long-term) perceptual memory across saccades, helping to preserve stability during saccades. The distinction between the modes of communicating short- and long-term memory suggests that the two phenomena are mediated by distinct neuronal circuitry.

Manipulating attention facilitates cooperation

Cooperation is essential for human societies, but not all individuals cooperate to the same degree. This is typically attributed to individual motives - for example, to be prosocial or to avoid risks. Here, we investigate whether cooperative behavior can, in addition, reflect what people pay attention to and whether cooperation may therefore be influenced by manipulations that direct attention. We first analyze the attentional patterns of participants playing one-shot Prisoner’s Dilemma games and find that choices indeed relate systematically to attention to specific social outcomes, as well as to individual eye movement patterns reflecting attentional strategies. To test for the causal impact of attention independently of participants’ prosocial and risk attitudes, we manipulate the task display and find that cooperation is enhanced when displays facilitate attention to others’ outcomes. Machine learning classifiers trained on these attentional patterns confirm that attentional strategies measured using eye-tracking can accurately predict cooperation out-of-sample. Our findings demonstrate that theories of cooperation can benefit from incorporating attention and that attentional interventions can improve cooperative outcomes.

Sleep and Prodromal Synucleinopathies.

α-synucleinopathies are a complex group of progressive neurodegenerative disorders with an increasingly recognized long prodromal period, during which sleep dysfunction is a hallmark. Sleep disorders during the prodromal synucleinopathy period, primarily isolated rapid eye movement (REM) sleep behavior disorder (iRBD) and daytime hypersomnolence correlate best with the recently proposed "body-first" Lewy body disease progression. iRBD is the most widely recognized form of prodromal α-synucleinopathy, and patients with iRBD show abnormal α-synuclein in tissues and biofluids even in the absence of cognitive or motor symptoms. More importantly, individuals with iRBD have an elevated risk for near-term development of a clinically diagnosable symptomatic synucleinopathy. Other sleep disorders such as hypersomnia and circadian rhythm dysfunction also occur across the synucleinopathy spectrum, although their prognostic significance is less well understood than iRBD. Finally, isolated REM sleep without atonia may represent an even earlier stage of prodromal synucleinopathy, but further studies are needed.

An Identification Method for Road Hypnosis Based on XGBoost-HMM

Human factors are the most important factor in road traffic crashes. Human-caused traffic crashes can be reduced through the active safety system of vehicles. Road hypnosis is an unconscious driving state caused by the combination of external environmental factors and the driver’s psychological state. When drivers fall into a state of road hypnosis, they cannot clearly perceive the surrounding environment and make various reactions in time to complete the driving task, and driving safety is greatly affected. Therefore, road hypnosis identification is of great significance for the active safety of vehicles. A road hypnosis identification model based on XGBoost—Hidden Markov is proposed in this study. Driver data and vehicle data related to road hypnosis are collected through the design and conduct of vehicle driving experiments. Driver data, including eye movement data and EEG data, are collected with eye movement sensors and EEG sensors. A mobile phone with AutoNavi navigation is used as an on-board sensor to collect vehicle speed, acceleration, and other information. Power spectrum density analysis, the sliding window method, and the point-by-point calculation method are used to extract the dynamic characteristics of road hypnosis, respectively. Through normalization and standardization, the key features of the three types of data are integrated into unified feature vectors. Based on XGBoost and the Hidden Markov algorithm, a road hypnotic identification model is constructed. The model is verified and evaluated through visual analysis. The results show that the road hypnosis state can be effectively identified by the model. The extraction of road hypnosis-related features is realized in non-fixed driving routes in this study. A new research idea for road hypnosis and a technical scheme reference for the development of intelligent driving assistance systems are provided, and the life identification ability of the vehicle intelligent cockpit is also improved. It is of great significance for the active safety of vehicles.

The Effect of Suvorexant on Fear Extinction Recall: A Double-Blind Randomised Controlled Pilot Trial in Healthy Individuals.

Post-traumatic stress disorder (PTSD) is a highly debilitating condition that develops after trauma exposure. Dysregulation in extinction memory consolidation (i.e., the ability to remember that trauma-related stimuli no longer signal danger) is proposed to underlie PTSD development. Disruptions in rapid eye movement (REM) sleep are thought to be the key contributor to this dysregulation, as REM sleep is suggested to play a vital role in the processing of emotional memories. While previous literature has investigated the role of natural REM sleep variations or REM sleep disruptions on extinction recall capacities, none have attempted to increase REM sleep to improve extinction recall. In this pilot, randomised controlled trial, we investigated the effect of 20 mg suvorexant to increase REM sleep, 20 mg temazepam to decrease REM sleep, and a placebo on extinction recall in 30 healthy adults (age: M = 26.93 years, SD = 7.54). Overall, no difference in REM percentage (p = 0.68, η2 = 0.0.03, small effect), nor in extinction recall (p = 0.58, η2 = 0.04, small effect) was observed between the drug conditions. However, increased REM percentage was associated with decreased conditioned fear response at recall, indicating better extinction recall (β = -0.71, p = 0.03, ηp 2 = 0.10; moderate effect) across the sample. These findings suggest that increasing REM sleep in populations with REM disruptions such as PTSD to optimal levels could improve extinction recall. This underscores the potential of enhancing REM sleep as a therapeutic target for improving PTSD outcomes, warranting further investigation of suvorexant in clinical populations where REM sleep deficits are prevalent.

Post-operative oropharyngeal rehabilitation suppress oxidative stress and inflammation in obstructive sleep apnea patients with transoral robotic surgery.

Post-operative oropharyngeal rehabilitation suppress oxidative stress and inflammation in obstructive sleep apnea patients with transoral robotic surgery.

Joint examination of reflexive vertical saccades and small involuntary fixational saccades improves the classification of patients with progressive supranuclear palsy (PSP): a ROC study

A slowing of saccadic eye movements is one of the key symptoms of progressive supranuclear palsy and therefore represents a core functional domain of the current diagnostic criteria. However, there is considerable overlap between the saccade velocities of healthy people and patients in early stages. Therefore, a highly specific discrimination between patients and controls based on eye velocity often results in a considerable loss of sensitivity. Another symptom of progressive supranuclear palsy is a high frequency of square wave jerks formed by small involuntary fixational saccades. Using ROC analyses of 50 patients and 50 controls and focusing on points of 100 and 90% specificity or sensitivity, we investigated whether the velocity and gain data of visually guided reflexive saccades could be combined with each other and with parameters of fixational saccades to improve discriminability compared to considering saccade velocity alone. Both approaches were successful in patients with long disease duration but less so in cases of short duration. The displacement rate produced by square waves during fixation proved helpful because its frequency distributions in patients and controls had value ranges that were not shared by the two groups. This fact allowed an a priori classification of some subjects as either patients or controls. Modified ROC analyses using this a priori information are expected to work equally well in patients with short and long disease duration. In future studies it might be addressed if these methods can also improve the discrimination between PSP and other Parkinsonian disorders.

Non-nystagmus hyperkinetic eye movement disorders.

While nystagmus is an involuntary ocular movement relatively frequent, well described, and easily recognized by most practitioners, non-nystagmus hyperkinetic eye movement disorders (NHEMD) are less obvious and can be overlooked. NHEMD may arise from intrinsic abnormalities in ocular muscles and oculomotor nerves, brain and brainstem lesions, systemic diseases, dysimmune disorders, drugs or can even be functional in nature. Given that some treatable disorders initially manifest with NHEMD, their knowledge becomes crucial. This review aims to offer a practical and comprehensive guide to recognize specific types of NHEMD, to choose the appropriate diagnostic tests and treatments. The review approaches individual NHEMD based on the location of anatomical lesions and the underlying pathophysiological mechanisms; therefore, it begins with those arising from abnormalities in extraocular muscles or oculomotor nerves (as for example, superior oblique myokymia and ocular neuromyotonia), then moves to NHEMD due to brainstem and brain involvement (as for example, ocular bobbing, opsoclonus, and tonic downward gaze deviation). Lastly, functional NHEMD and nonnystagmus ocular hyperkinesias associated with specific neurological disorders, such as Parkinson's disease or blepharospasm will be considered. Overall, the review offers a comprehensive reappraisal of hyperkinetic disorders of eye motility.

The Gut-Brain Axis in Parkinson disease: Emerging Concepts and Therapeutic Implications.

The gut-brain axis, i.e. the bidirectional communication system between the gut and the brain, has become of central importance in Parkinson disease (PD) research over the past 20 years. We aimed to describe the milestones of the gut-brain axis research in PD and the development of theories proposing the involvement of the gastrointestinal tract in PD pathogenesis. We searched PubMed using the terms 'gut-brain axis' AND 'Parkinson disease', and selected relevant articles to provide the foundation for reconstructing an historical overview of the gut-brain axis research in PD. Mounting evidence from preclinical, clinical and post-mortem studies suggests that a subgroup of PD patients present with a range of prodromal symptoms (e.g., autonomic dysfunction, rapid eye movement sleep behaviour disorder) which reflect initial accumulation and later spread of pathological α-synuclein rostrally from the gastrointestinal tract ("body-first" PD). Through neural connections along the gut-brain axis, pathological α-synuclein may spread to the brain, producing clinically manifest disease. Recently, two mechanisms involving the gut-brain axis have attracted increasing attention for their role in PD pathogenesis and progression, namely the perturbation of the composition of the microorganisms living in the gut (the gut microbiome), and the dysfunction of enteroendocrine cells. Treatments targeting the gut-brain axis, especially the gut microbiome and the enteroendocrine cells pathway, could potentially slow disease progression or even prevent disease onset. Among these, pre/probiotics, faecal microbiota transplantation, and glucagon-like peptide-1 receptor agonists, have entered advanced stages of clinical trials in humans and shown potential symptomatic and disease-modifying effects.

Mission Responses of Special Vehicle Crews: Effects of Experience Levels and Substitutability in High-Demand Visual/Motion Tasks

The study of special vehicle crews' mission responses is essential for optimizing their working conditions and enhancing combat effectiveness. This study investigates the physiological, behavioral, and subjective workload responses of crews with varying experience levels in visual/motion tasks with different demands. A virtual simulation system was employed with 120 participants categorized into professionals, short-term trainees, and novices. EEG, eye movement and NASA-TLX scores were measured across task conditions. Results indicate that as crew experience increases, NASA-TLX scores decrease, physiological responses stabilize, but task completion times lengthen, with distinct behavioral patterns. Novices in low-demand motion tasks produce physiological data statistically like professionals. Short-term trainees in high-demand motion tasks produce coefficient of variation results of physiological data statistically like professionals. These findings suggest that short-term trainees can substitute for professionals in high-demand motion mechanical tasks, with implications for research data reliability assessment and increasing training and operational efficiency.

Is Ocular Counter-Roll Otolith-Ocular Reflex?

Purpose Ocular counter-roll has been thought to be an otolith-ocular reflex. However, there is a hypothesis that it is a semicircular canal (SCC) ocular reflex. This study aimed to validate whether ocular counter-roll can be explained by the SCC theory. Methods Experiment 1: Two springs with plastic balls (different turning radius) were fixed to a swivel chair and were rotated suddenly. Experiment 2: Subject was seated and the entire upper body was bent forward 60 degrees with the neck fixed. Experiment 3: Subject was seated, the head was twisted 45 degrees to the right and the entire upper body was bent forward 60 degrees with the neck fixed. Experiment 4 (roll rotation): Subject was asked to tilt his upper body 60 degrees to the left. Eye movements in the dark were observed and recorded using an infrared camera. In Experiments 2, 3 and 4, subjects were four healthy humans. Results Experiment 1: Immediately after the movement, the two balls moved tangentially. The ball on the outside spring moved more compared to the ball attached to the inside spring. Experiment 2: In all subjects, nystagmus was vertical. The direction was downward. Experiment 3: In all subjects, nystagmus was vertical/torsional. The direction was downward (torsional component was leftward). Experiment 4: In all subjects, nystagmus was torsional, and the direction was leftward. Conclusion Since the role of SCCs is to sense angular acceleration in all directions of 360 degrees in a coordinated manner, bilateral vertical SCCs are stimulated in roll rotation. Therefore, SCC theory can explain the generation of ocular counter-roll. We proposed the “difference of inertial forces” theory to explain the mechanism of vestibulo-ocular reflex.

Electrophysiological signatures underlying variability in human memory consolidation

We experience countless pieces of new information each day, but remembering them later depends on firmly instilling memory storage in the brain. Numerous studies have implicated non-rapid eye movement (NREM) sleep in consolidating memories via interactions between hippocampus and cortex. However, the temporal dynamics of this hippocampal-cortical communication and the concomitant neural oscillations during memory reactivations remains unclear. To address this issue, the present study used the procedure of targeted memory reactivation (TMR) following learning of object-location associations to selectively reactivate memories during human NREM sleep. Cortical pattern reactivation and hippocampal-cortical coupling were measured with intracranial EEG recordings in patients with epilepsy. We found that TMR produced variable amounts of memory enhancement across a set of object-location associations. Successful TMR increased hippocampal ripples and cortical spindles, apparent during two discrete sweeps of reactivation. The first reactivation sweep was accompanied by increased hippocampal-cortical communication and hippocampal ripple events coupled to local cortical activity (cortical ripples and high-frequency broadband activity). In contrast, hippocampal-cortical coupling decreased during the second sweep, while increased cortical spindle activity indicated continued cortical processing to achieve long-term storage. Taken together, our findings show how dynamic patterns of item-level reactivation and hippocampal-cortical communication support memory enhancement during NREM sleep.

Dual-filament regulation of relaxation in mammalian fast skeletal muscle

Muscle contraction is driven by myosin motors from the thick filaments pulling on the actin-containing thin filaments of the sarcomere, and it is regulated by structural changes in both filaments. Thin filaments are activated by an increase in intracellular calcium concentration [Ca2+]i and by myosin binding to actin. Thick filaments are activated by direct sensing of the filament load. However, these mechanisms cannot explain muscle relaxation when [Ca2+]i decreases at high load and myosin motors are attached to actin. There is, therefore, a fundamental gap in our understanding of muscle relaxation, despite its importance for muscle function in vivo, for example, for rapid eye movements or, on slower timescales, for the efficient control of posture. Here, we used time-resolved small-angle X-ray diffraction (SAXD) to determine how muscle thin and thick filaments switch OFF in extensor digitorum longus (EDL) muscles of the mouse in response to decreases in either [Ca2+]i or muscle load and to describe the distribution of muscle sarcomere lengths (SLs) during relaxation. We show that reducing load at high [Ca2+]i is more effective in switching OFF both the thick and thin filaments than reducing [Ca2+]i at high load in normal relaxation. In the latter case, the thick filaments initially remain fully ON, although the number of myosin motors bound to actin decreases and the force per attached motor increases. That initial slow phase of relaxation is abruptly terminated by yielding of one population of sarcomeres, triggering a redistribution of SLs that leads to the rapid completion of mechanical relaxation.

Evaluation of Phosphene Shifts During Eye Movements to Enhance Safe Visual Assistance for Visually Impaired Individuals

Hands-free visual assistive devices that consider the safety of the visually impaired have been researched, but many of them interfere with other senses, such as hearing. Therefore, phosphenes have been researched as a method of presenting visual information. Phosphenes are flashes that are recognized by electrical stimulation, and the presentation position can be adjusted by the electrode arrangement. However, it has been reported that the presentation position changes significantly when the eyeballs are moved as far left and right as possible. As a walking assistive device for the visually impaired, the fluctuation of the presentation position of phosphenes may cause safety problems. This study used the Hess test to verify the positional fluctuation of phosphenes associated with eye movement and compared it with eye movement during walking to discuss safety. As a result, the range of the change in the presentation position of phosphenes was significantly large when subjects moved their eyes to the peripheral vision, the same as in the previous study. On the other hand, the presentation position of phosphenes did not change significantly within the range of eye movement during walking (±15 deg). Our results suggest that there is the possibility that serious safety issues will not happen with assistive devices for the visually impaired who use phosphenes.

Enhancing multimodal deepfake detection with local–global feature integration and diffusion models

Deepfake detection has become a critical challenge nowadays with the rise of sophisticated generative techniques that manipulate audio-visual data. Existing methods primarily focus on lip movement synchronization using audio and visual features, often relying on local feature extraction with Convolutional Neural Networks (CNNs). In this work, we propose an enhanced multimodal framework that integrates with local and global features for advanced deepfake detection. Our approach extends traditional pipelines by introducing additional visual features such as eye movement and facial regions, combined with audio features to model cross-modal dependencies. While CNNs capture local features, Vision Transformers (ViTs) extract global contextual relationships from both visual and audio modalities. The diffusion models are incorporated as pre-processors to refine noisy data and generate realistic augmentations, ensuring high-quality feature representation. The proposed framework achieves state-of-the-art performance, with accuracy scores of 0.9987, 0.9825, 0.9915, and 0.9812 on the FakeAVCeleb, AV-Deepfake1M, TVIL, and LAV-DF datasets, respectively. These results demonstrate significant improvements over existing methods, highlighting the framework’s superior generalization and robustness in detecting subtle inconsistencies across manipulated audio-visual data.

EXPRESS: Individuals with developmental prosopagnosia tend to focus more evenly on facial features.

The causes of developmental prosopagnosia (DP) have long been a focus of research; however, the cause has not been conclusively identified. This study uses behavioral and eye movement techniques to explore the causes of DP by comparing differences in fixation patterns during face recognition between the DP and control groups. A mixed experimental design of 2 (group: control, DP) x 3 (area of interest (AOI): eyes, nose, mouth) was adopted, dividing faces into 3 AOIs: eyes, nose, and mouth. The behavioral results showed that the face recognition scores were lower in the DP group than in the control group. The eye movement results showed that the duration and number of eye and nose fixations were greater than those on the mouth in the control group; however, the duration and number of fixations on the eyes, nose, and mouth did not differ in the DP group. The results confirmed that the control group focused more on the eye and nose when recognizing faces, while the DP group adopted a more even browsing pattern to focus on various facial features.