Phasic events, cyclic alternating pattern (CAP) and sleep disorders.

Sleeping with your eyes open: a fortuitous case of nocturnal lagophthalmos.

Sleepiness at the wheel is an important contributor to road traffic accidents. Slow eye movement (SEM) serves as a reliable physiological indicator for the sleep onset period (SOP). To detect SEM for recognizing drivers’ SOP, a Parallel Multimodal CNN-Transformer (PMMCT) model is proposed. The model employs two parallel feature extraction modules to process bimodal signals, each comprising convolutional layers and Transformer encoder layers. The extracted features are fused and then classified using fully connected layers. The model is evaluated on two bimodal signal combinations HEOG + O2 and HEOG + HSUM, where HSUM is the sum of two single-channel horizontal electrooculogram (HEOG) signals and captures electroencephalograph (EEG) features similar to those in the conventional O2 channel. Experimental results indicate that using the PMMCT model, the HEOG + HSUM combination performs comparably to the HEOG + O2 combination and outperforms unimodal HEOG by 2.73% in F1-score, with average classification accuracy and F1-score of 99.89% and 99.35%, outperforming CNN, CNN-LSTM, and CNN-LSTM-Attention models. The model exhibits minimal false positives and false negatives, with average values of 5.2 and 0.8. By combining CNNs’ local feature extraction with Transformers’ global temporal modeling, and using only two HEOG electrodes, the system offers superior performance while enhancing wearable device comfort for real-world applications.

Somatosensory mediated reactions play a fundamental role in adapting to environmental changes, particularly through long-latency responses (LLRs)-rapid corrective muscle responses (50-100ms) following limb perturbations that account for limb biomechanics and task goals. We investigated how smooth pursuit eye movements (SPEM), which are slow eye movements used to track moving objects, influence LLRs of the upper and lower limb during mechanical interactions with moving objects. In the first experiment, participants stood and stabilized their arm against a colliding virtual object. This occurred while subjects either visually pursued the moving object or fixated a central location. The robot occasionally applied a mechanical perturbation to the arm either 200ms or 60ms before the anticipated collision. As in previous studies, LLRs were observed in leg muscles to a perturbation of the upper limb. Moreover, leg LLRs were modulated by gaze, being larger during pursuit than fixation but only during the late perturbations. This timing-specific modulation aligns with previous reports of policy transitions in feedback control roughly 60ms before impact. Upper limb LLRs were not significantly impacted by gaze. This lack of modulation could reflect the context of upright stance, so we conducted a second experiment which was the same in all ways except that the subjects remained seated. Again, the upper limb LLRs were not impacted by gaze. The selective impact of gaze modulation on stance control highlights the sophisticated nature of coordinating eye movements, arm control, and whole-body postural responses.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant cerebellar ataxia caused by abnormal CAG expansions (≥ 34 repeats) in the ATXN2 gene (ATXN2), whereas intermediate CAG expansions (27-33 repeats) have been linked to amyotrophic lateral sclerosis (ALS). A 53-year-old woman with longstanding cerebellar ataxia developed progressive upper limb weakness and muscle atrophy at the age of 51years. On neurological examination, she was found to have ataxic dysarthria, slow saccadic eye movements, tongue atrophy with fasciculations, muscle atrophy and weakness in both upper limbs, hyperreflexia with Babinski's sign, and limb and gait ataxia. Brain magnetic resonance imaging (MRI) showed brainstem and cerebellar atrophy. Genetic analysis identified an expanded CAG-repeat of 39/22 in ATXN2, and screening for other known ALS-related gene mutations was negative, leading to a diagnosis of both SCA2 and ALS associated with ATXN2. SCA2 is typically associated with uninterrupted CAG-repeat expansions, whereas ALS-related ATXN2 expansions usually contain at least one CAA triplet. However, despite carrying an uninterrupted CAG-repeat expansion, this patient developed ALS. This case shows that ALS can emerge several decades after SCA2 onset, even in patients with pure CAG-repeats, underscoring the need for long-term monitoring in SCA2 patients. Further research is needed to clarify the roles of repeat length, CAA interruptions, and other factors in ATXN2-related ALS.

Study ObjectivesHealthy older adults appear more resilient to sleep loss relative to younger adults, particularly with respect to the likelihood of falling asleep. We examined task-dependent differences in age-related vulnerability to sleep deprivation focusing on outcomes reflecting sleep-initiation (microsleep, slow eye movements [SEMs], electroencephalography [EEG] delta power, and long lapses > 3 s) versus other non-sleep-initiation aspects of impairment (adjusted mean RT/lapses, reflexive attention, and inhibitory control).MethodsSeventeen younger (M = 24.5 ± 3.2 years [range 21–33 years], 10 males) and 17 older (M = 57.3 ± 5.2 years [range 50–65 years], 9 males) healthy adults underwent 26 h of sleep deprivation. Test batteries (psychomotor vigilance test [PVT], Karolinska drowsiness test, and ocular motor paradigms) with simultaneous EEG were administered at regular intervals throughout.ResultsDuring sleep deprivation, younger adults had significantly more sleep-initiation events relative to older adults (p < .031) including EEG microsleep (average 4.4 vs. 1.1), SEMs (10.7 vs. 4.9), and relative delta power (38.1 vs. 24.2%). For non-sleep-initiation outcomes, interaction effects were not observed. Both younger and older groups had slower reflexive attention (4.2 and 3.1 ms, respectively) and poorer inhibitory control (8.6% and 9% more errors) during sleep deprivation relative to when well-rested (p < .001), with older adults being more impaired than younger adults overall (p < .001). Large inter-individual differences in sleep-initiation events were observed for younger adults. Preliminary results suggest women exhibited age-related differences in all sleep-initiation events (Hedges’ g = 0.73 to 1.64), while men did not (g = 0.12 to 0.34).ConclusionsYounger adults are more likely to fall asleep during sleep deprivation, particularly women, while older adults may be more likely to exhibit attentional control difficulties.

The adenoma detection rate is higher among endoscopists who spend more time observing screen edges during colonoscopies. Nonetheless, eye movement parameters related to lesion detection remain unknown. This study aimed to determine the specific eye movement parameters related to colorectal adenoma detection, including the gaze rate in a particular area and eye movement speed. This study was a post hoc analysis of a randomized controlled trial investigating the effect of modifying eye movements of endoscopists on colorectal adenoma detection. Gaze rate at a specific area and eye movement speed were calculated based on endoscopist gaze coordinates in each examination. Time required for observation and treatment of polyps was excluded. The lower peripheral area was defined as the bottom row when the screen was divided into 6×6 sections. These parameters were compared between patients with and without adenomas. Five physicians performed 158 colonoscopies. The adenoma detection group exhibited a lower peripheral gaze rate (13.7% vs. 9.5%, P = 0.004) and smaller average eye movement distance (29.9 pixels/30 ms vs. 33.3 pixels/30 ms, P = 0.022). Logistic regression analysis showed that a lower peripheral gaze rate > 13.0% and an average eye movement distance <30 pixels/30 ms were increased independent predictors of adenoma detection ( P = 0.024, odds ratio [OR] 2.53, 95% confidence interval [CI] 1.71-3.28; P = 0.045, OR 4.57, 95% CI 1.03-20.2), whereas age, sex, and withdrawal time were not. Lower peripheral gaze rate and slow eye movement are associated with colorectal adenoma detection.

Slow eye movements (SEMs) are a reliable physiological marker of drivers' sleep onset, often accompanied by EEG alpha wave attenuation. A parallel multimodal 1D convolutional neural network (PM-1D-CNN) model is proposed to classify SEMs. The model uses two parallel 1D-CNN blocks to extract features from EOG and EEG signals, which are then fused and fed into fully connected layers for classification. Results show that the PM-1D-CNN outperforms the SGL-1D-CNN and Bimodal-LSTM networks in both subject-to-subject and cross-subject evaluations, confirming its effectiveness in detecting sleep onset.

The appearance of an object triggers an orienting gaze movement toward its location. The movement consists of a rapid rotation of the eyes, the saccade, which is accompanied by a head rotation if the target eccentricity exceeds the oculomotor range and by a slow eye movement if the target moves. Completing a previous report, we explain the numerous points that lead to questioning the validity of a one-to-one correspondence relation between measured physical values of gaze or head orientation and neuronal activity. Comparing the sole kinematic (or dynamic) numerical values with neurophysiological recordings carries the risk of believing that the activity of central neurons directly encodes gaze or head physical orientation rather than mediating changes in extraocular and neck muscle contraction, not to mention possible changes happening elsewhere (in posture, in the autonomous nervous system and more centrally). Rather than reducing mismatches between extrinsic physical parameters (such as position or velocity errors), eye and head movements are behavioral expressions of intrinsic processes that restore a poly-equilibrium, i.e., balances of activities opposing antagonistic visuomotor channels. Past results obtained in cats and monkeys left a treasure of data allowing a synthesis, which illustrates the formidable complexity underlying the small changes in the orientations of the eyes and head. The aim of this synthesis is to serve as a new guide for further investigations or for comparison with other species.

Abstract BackgroundAlzheimer’s disease can cause sleep disturbances in humans, which can worsen other symptoms of the disease.MethodIn our study, we examined the sleep patterns of 23 patients with Alzheimer’s disease, aged 65‐74 years (20 women and 3 men), over 4 months. All patients reported experiencing poor sleep, including difficulty sleeping in the ward, frequent awakenings during the night, early morning awakenings, and daytime sleepiness. To assess their sleep, we conducted a polysomnographic study in a specialized ward with continuous monitoring of indicators, video, and audio control. This was done both before the patients were included in the study and after a month of melatonin administration. During the diagnostic night, a nurse was present to continuously observe the polysomnography process. Based on the results of the polysomnography, we constructed a hypnogram, which is a curve that depicts the quality of sleep, the number and duration of sleep stages, and their structure. The patients were given a dose of 1.5 mg of melatonin (half a tablet) 30 minutes before bedtime for 4 weeks, with gradual withdrawal.ResultIn the initial polysomnographic study, all patients showed shortened phases of rapid eye movement (REM) and slow eye movement (SEM), with a rapid transition between them during sleep. They also experienced long periods before falling asleep and 3 to 4 nocturnal awakenings. However, after a month of melatonin administration, the majority of patients showed a normalization of REM and SEM phases, in line with their age norms, and an improvement in the duration of sleep. The number of nocturnal awakenings also decreased to 1‐2, mostly between 4 and 6 hours. Additionally, patients were able to fall back asleep after awakening, and the time it took for them to fall asleep decreased. However, even after a month of melatonin supplementation, some patients still experienced early morning awakenings and daytime sleepiness and reported feeling unrefreshed after a night’s sleep.ConclusionIn conclusion, our study suggests that melatonin is effective in treating sleep disorders in patients with Alzheimer’s disease, and can help normalize the duration and frequency of REM and SEM phases during sleep.

Abstract Aims Dolphins sleep one half of their brain at a time presumably to avoid drowning – called unihemispheric slow wave sleep. The Northern Fur Seal has been reported to do this whilst in the water but sleep bihemispherically when it is terrestrial. These observations made us wonder whether unihemispheric slow wave might be an evolutionarily conserved ability in humans that might be revealed if we simply slept in water. Methods We built a waterproof and temperature regulated housing to protect an EEG recorder (Alice PDX, Respironics) from being near a float tank (AKA floatation REST therapy) with very low level light and sound levels and thermoneutral temperature. Float therapy uses a highly concentrated Epsom salt solution making the human body extremely buoyant. Reports of single channel automatically processed EEG being measured in float tanks convinced us we could try to find unihemispheric slow wave in a human sleeping in water. Active EEG placements were recorded at Fp1 and Fp2 both referenced to Fpz on the forehead. Left and right electrooculogram (EOG) was also recorded referenced to Fpz. EEG was scored using Alice G3 Sleepware 3.9.5 (Philips Respironics Pittsburgh, USA) following the scoring manual American academy of sleep medicine. A single male human with previous float tank experience was recorded in the float tank in the morning (1 hour). Results We captured scorable EEG and detected stage 2 sleep characteristic K complexes and sleep spindles. At no point did we detect slow wave sleep or uni-hemispheric sleep. Slow waves around sleep onset are artifactual slow rolling eye movements being detected in these frontal channels. Discussion It is possible to record EEG and score human sleeping in water. We saw no asymmetry in the stage 2 sleep but captured no SWS to compare to see whether humans sleep like dolphins in water.

Saccades, pupil response and blink abnormalities in Huntington’s disease patients during free viewing

The posterior parietal cortex (PPC) integrates multisensory and motor-related information for generating and updating body representations and movement plans. We used retrograde transneuronal transfer of rabies virus combined with a conventional tracer in macaque monkeys to identify direct and disynaptic pathways to the arm-related rostral medial intraparietal area (MIP), the ventral lateral intraparietal area (LIPv), belonging to the parietal eye field, and the pursuit-related lateral subdivision of the medial superior temporal area (MSTl). We found that these areas receive major disynaptic pathways via the thalamus from the nucleus of the optic tract (NOT) and the superior colliculus (SC), mainly ipsilaterally. NOT pathways, targeting MSTl most prominently, serve to process the sensory consequences of slow eye movements for which the NOT is the key sensorimotor interface. They potentially contribute to the directional asymmetry of the pursuit and optokinetic systems. MSTl and LIPv receive feedforward inputs from SC visual layers, which are potential correlates for fast detection of motion, perceptual saccadic suppression and visual spatial attention. MSTl is the target of efference copy pathways from saccade- and head-related compartments of SC motor layers and head-related reticulospinal neurons. They are potential sources of extraretinal signals related to eye and head movement in MSTl visual-tracking neurons. LIPv and rostral MIP receive efference copy pathways from all SC motor layers, providing online estimates of eye, head and arm movements. Our findings have important implications for understanding the role of the PPC in representation updating, internal models for online movement guidance, eye-hand coordination and optic ataxia.

This is a personal review of a research life focused on sleep in everyday life. It finds that irregular work hours shorten sleep duration and increase sleepiness, both subjectively and objectively (polysomnography). Also, experimental lab studies demonstrate reduced sleep duration (and sleep stages N2 and REM) when sleep is moved into the daylight hours (and the circadian upswing). Stage N3% seems not affected, and homeostatic experiments suggest that awakenings should not occur until the need for N3% or total spectral power has been satisfied. Furthermore, sleepiness is associated with increased alpha activity and slow eye movements, although the best indicator of dangerous sleepiness is subjective ratings (linked to perceptions of heavy eye lids). Everyday stress has very modest negative effects on objective sleep quality. Sleep loss as well as excessive sleep durations are linked to mortality, but with modest risk, and mainly in older individuals. Finally, objective sleep poorly reflects subjective sleep quality, and women appear to report poorer sleep than men, while objective data show better sleep quality in women. The discrepancy is considerably greater in older age groups.

Following previous studies documenting the ability to generate anticipatory responses, we tested whether the repeated motion of a visual target along the same path affected its oculomotor tracking. In six rhesus monkeys, we evaluated how the frequency of a target path influenced the onset, accuracy, and velocity of eye movements. Three hundred milliseconds after its extinction, a central target reappeared and immediately moved toward the periphery in four possible (oblique) directions and at a constant speed (20°/s or 40°/s). During each daily session, the frequency of one motion direction was either uncertain (25% of trials) or certain (100% of trials). Our results show no reduction of saccade latency between the two sessions. No express saccades were observed in either session. A slow eye movement started after target onset (presaccadic glissade) and its velocity was larger during the "certain" sessions only with the 40°/s target. No anticipatory eye movement was observed. Longer intersaccadic intervals were found during the "certain" sessions but the postsaccadic pursuit velocity exhibited no change. No correlation was found between the accuracy and precision of saccades (interceptive or catch-up) and the postsaccadic pursuit velocity. Repeatedly tracking a target that moves always along the same path does not favor the generation of anticipatory eye movements, saccadic or slow. Their occurrence is not spontaneous but seems to require preliminary training. Finally, for both sessions, the lack of correlation between the saccade-related and pursuit-related kinematic parameters is consistent with separate control of saccadic and slow eye movements.NEW & NOTEWORTHY Following previous studies documenting anticipatory movements, we investigated how the frequency of occurrence of a target path influenced the generation of tracking eye movements. When present, the effects were small. The limited performance that we found suggests that anticipatory responses require preliminary training, in which case, they should not be considered as a behavioral marker of the primates' ability to extrapolate but the outcome of learning and remembering past experience.

The ultimate role of ocular movements is to keep the image of an object within the fovea and thereby prevent image slippage on the retina. Accurate evaluations of eye movements provide very useful information for understanding the functions of the oculomotor system and determining abnormalities therein. Such evaluations also play an important role in enabling accurate diagnoses by identifying the location of lesions and discriminating from other diseases. There are various types of ocular movements, and this article focuses on saccades, fast eye movements, smooth pursuit, and slow eye movements, which are the most important types of eye movements used in evaluations performed in clinical practice.

Identification of full-night sleep parameters using morphological features of ECG signals: A practical alternative to EEG and EOG signals

Dissociative disorders (DDs) are characterized by a discontinuity in the normal integration of consciousness, memory, identity, emotion, perception, bodily representation, motor control, and action. The life-threatening coronavirus disease 2019 (COVID-19) pandemic has been identified as a potentially traumatic event and may produce a wide range of mental health problems, such as depression, anxiety disorders, sleep disorders, and DD, stemming from pandemic-related events, such as sickness, isolation, losing loved ones, and fear for one's life. In our conceptual analysis, we introduce the contribution of the structural dissociation of personality (SDP) theory and polyvagal theory to the conceptualization of the COVID-19 pandemic-triggered DD and the importance of assessing perceived safety in DD through neurophysiologically informed psychometric tools. In addition, we analyzed the contribution of eye movement desensitization and reprocessing (EMDR) to the treatment of the COVID-19 pandemic-triggered DD and suggest possible neurobiological mechanisms of action of the EMDR. In particular, we propose that, through slow eye movements, the EMDR may promote an initial non-rapid-eye-movement sleep stage 1-like activity, a subsequent access to a slow-wave sleep activity, and an oxytocinergic neurotransmission that, in turn, may foster the functional coupling between paraventricular nucleus and both sympathetic and parasympathetic cardioinhibitory nuclei. Neurophysiologically informed psychometric tools for safety evaluation in DDs are discussed. Furthermore, clinical and public health implications are considered, combining the EMDR, SDP theory, and polyvagal conceptualizations in light of the potential dissociative symptomatology triggered by the COVID-19 pandemic.

Detecting slow eye movements using multi-scale one-dimensional convolutional neural network for driver sleepiness detection

Driver drowsiness is a widely recognized cause of motor vehicle accidents. Therefore, a reduction in drowsy driving crashes is required. Many studies evaluating the crash risk of drowsy driving and developing drowsiness detection systems, have used observer rating of drowsiness (ORD) as a reference standard (i.e. ground truth) of drowsiness. ORD is a method of human raters evaluating the levels of driver drowsiness, by visually observing a driver. Despite the widespread use of ORD, concerns remain regarding its convergent validity, which is supported by the relationship between ORD and other drowsiness measures. The objective of the present study was to validate video-based ORD, by examining correlations between ORD levels and other drowsiness measures. Seventeen participants performed eight sessions of a simulated driving task, verbally responding to Karolinska sleepiness scale (KSS), while infra-red face video, lateral position of the participant's car, eye closure, electrooculography (EOG), and electroencephalography (EEG) were recorded. Three experienced raters evaluated the ORD levels by observing facial videos. The results showed significant positive correlations between the ORD levels and all other drowsiness measures (i.e., KSS, standard deviation of the lateral position of the car, percentage of time occupied by slow eye movement calculated from EOG, EEG alpha power, and EEG theta power). The results support the convergent validity of video-based ORD as a measure of driver drowsiness. This suggests that ORD might be suitable as a ground truth for drowsiness.