Rapid Eye Movement (REM) sleep alternates between two states - phasic and tonic - defined by the presence or absence of transient neurophysiological events such as rapid eye movements. These states exhibit distinct neural activity and putative underlying function, yet their evolution along with aging remains unknown. Retrospective polysomnographic data from 627 healthy participants (290 females and 337 males), aged 18 to 80 years and drawn from five databases, were analyzed to characterize age- and sex-related changes in the REM sleep microstructure. REM sleep macrostructure declined with age, paralleled by a reduction in phasic REM duration. In addition, the proportion of phasic REM sleep as well as the number and density of eye movements decreased with advancing age. We found sex-related differences in these trajectories, with a steeper decline in phasic REM percentage and REM density in women. Spectral analyses mainly confirmed previously reported differences in power between phasic and tonic states and further revealed differential age-related changes, i.e., while spectral power in tonic REM increased in higher frequency bands, phasic REM exhibited a progressive slowing of EEG activity across the lifespan. This large-scale, multicohort analysis provides a comprehensive characterization of REM sleep microstructure across aging and between sexes in healthy participants, constituting an important step toward its potential as a biomarker candidate in psychopathological and neurodegenerative disorders.

Objective Heart rate variability biofeedback (HRV-BFB) is a nonpharmacological treatment used to improve both autonomic nervous system (ANS) functioning and mental health. Nevertheless, evidence-based approaches are needed to demonstrate that HRV-BFB effects are over and above the placebo effect. Further evidence of its efficacy during emotional tasks is also required. The aim of our randomized controlled trial was therefore to examine HRV-BFB effects on the psychophysiological states of healthy adults against a valid sham condition. Method Participants (N=47) underwent three assessments spaced 24 days apart. Psychological states were estimated (affectivity, anxiety, depression, perceived stress, coping, life satisfaction). Aspects of ANS activity (HRV, electrodermal activity) were then recorded at rest, in reactivity during an overload mental task, and in recovery from it. After a 24-day pre-training period, participants were randomly assigned to either the HRV-BFB group (n = 24, Mage = 35.00, five males) or the sham HRV-BFB group (n = 23, Mage = 28.00, five males) and had to practice daily for 5min, three times a day, during a 24-day training period. Results HRV-BFB improved positive affectivity and reduced depression in comparison with sham HRV-BFB, but did not modulate ANS (rest / reactivity / recovery). Exploratory analyses indicated that a higher respiratory-mediated HRV during HRV-BFB practice did not systematically correspond to maximized psychological benefits. Conclusion: The effects of HRV-BFB are greater than those of sham HRV-BFB for reducing psychological distress. We discuss potential mechanisms underlying HRV-BFB’s benefits and its relevance as an evidence-based nonpharmacological treatment.

Objectif Le sommeil paradoxal (REM) présente une microstructure composée de deux états, se distinguant par la présence (i.e., phasique) ou l’absence (i.e., tonique) de manifestations neurophysiologiques transitoires telles que les mouvements oculaires rapides (MOR). Ces deux états sont associés à des caractéristiques électrophysiologiques et fonctionnelles différentes. Néanmoins, l’évolution de ces deux micro-états au cours de la vie reste encore insuffisamment documentée. Cette étude vise à caractériser l’évolution de la microstructure du sommeil REM avec l’âge, au travers de différents indicateurs microstructuraux, sur une large cohorte de données de sommeil rétrospectives. Méthodes Les données rétrospectives de 627 participants sains âgés de 18 à 80 ans ont été réanalysées à l’aide d’un système de détection automatisée des mouvements oculaires. Cette détection a permis de comptabiliser les MOR, ainsi que de quantifier les périodes phasiques et toniques au cours du sommeil REM. Une analyse de puissance spectrale a également été effectuée en sommeil REM phasique vs. tonique. Résultats Les durées des périodes phasiques et toniques diminuent avec l’âge, parallèlement à la réduction globale du temps de sommeil REM. La proportion de sommeil REM diminue progressivement avec l’âge, tandis que la densité de MOR (i.e., REM density) reste stable. Des différences liées au sexe ont été observées, avec une baisse plus marquée du pourcentage de REM phasique et de la densité de MOR chez les femmes, tandis que la densité de MOR augmente avec l’âge chez les hommes. Les analyses spectrales ont confirmé les différences de puissance précédemment rapportées entre les états phasiques et toniques, et ont en outre révélé un ralentissement progressif avec l’âge de l’activité EEG uniquement en sommeil REM phasique. Conclusion Ces résultats soulignent l’importance d’une approche microstructurale du sommeil paradoxal, mettant en lumière des dynamiques évolutives distinctes de la macro-architecture globale, tant au niveau de l’activité oculaire que de la puissance spectrale. Ils illustrent également l’apport d’un système automatisé de détection des MOR, rendant possible des analyses reproductibles et sur larges cohortes. Ces résultats constituent une base solide pour identifier des altérations microstructurales dans des troubles psychopathologiques et neurodégénératifs.

The gastric's intrinsic slow-wave rhythm couples to ongoing cortical activity in humans, but the functional significance of this gastric-brain coupling remains poorly understood. Using simultaneous electroencephalography and electrogastrography, we examined how gastric-brain coupling changes during a mental task and subsequent recovery and whether these dynamics relate to autonomic responses in healthy adults (HA) and individuals with Irritable Bowel Syndrome (IBS), a disorder of gut-brain interactions. In HA, gastric-brain coupling decreased during mental task and gradually returned to baseline during recovery, primarily for cortical alpha rhythms. Greater reductions in gastric-brain coupling were associated with stronger sympathetic arousal, indicating that gastric-brain coupling is associated with physiological responses to cognitive demand. In IBS, gastric-brain coupling dynamics were preserved. However, unlike HA, sympathetic arousal was not associated with gastric-brain coupling reductions, suggesting an alteration in the functional relationship between gastric-brain coupling and autonomic regulation despite preserved coupling dynamics. Further, in HA, greater reductions in gastric-brain coupling were associated with higher anxiety and neuroticism and lower interoceptive awareness. In contrast, these relationships were reversed in IBS, with greater gastric-brain coupling dynamics observed in individuals with higher anxiety and neuroticism and lower interoceptive awareness. Together, gastric-brain coupling emerges as a dynamic physiological process associated with autonomic responses to cognitive demand. In IBS, these dynamics are preserved but their physiological and psychological associations are altered, indicating a dissociation between gastric-brain coupling and its functional correlates.

Cognitive-motor dual-task (CMDT) is essential in military operations, yet it remains unknown whether soldiers cope with fatigue, important perceived exertion and cognitive degradation differently from fitness-matched civilians. This study compared sustained attention, neuromuscular fatigue and perceived effort during an incremental cycling and cognitive test (ICCT) in soldiers versus fitness-matched civilians. Thirty-two trained participants (13 soldiers) performed the ICCT, consisting of 3-min CMDT stages with increasing cycling power (starting at 1 W∙kg−1, + 0.4 W∙kg−1/stage) until task-failure. Sustained attention was assessed with the Mackworth task. Neuromuscular fatigue was measured via isometric knee-extensor maximal voluntary contraction (IMVC) and femoral nerve stimulation (peak twitch, Pt; voluntary activation, VA). Cycling and mental effort were rated using 100-points Borg scale. Cycling power and heart rate at task-failure were comparable between groups (all P ≥ 0.13). Mackworth performance was similarly impaired at task-failure (P = 0.47). IMVC and VA declines throughout the ICCT were comparable between groups (P ≥ 0.25), but Pt decreased more in soldiers (-53 ± 15

Irritable bowel syndrome [IBS] is classified as a disorder of gut-brain interaction related to stress with no curative option. Heart rate variability biofeedback [HRV-BFB] is a non-drug therapy recently suggested to be relevant in reducing both autonomic nervous system [ANS] dysregulations and psychiatric comorbidities. Nevertheless, empirical evidence is still scarce and only a few studies have tested HRV-BFB in adults with IBS. Our aims were therefore to examine the effectiveness of HRV-BFB training on the psychophysiological states of 29 adults with IBS. The study took place in three sessions, spaced 24 days apart. In all sessions, participants completed self-report questionnaires to assess their psychological state (affectivity, anxiety, depression, perceived stress, coping strategy, life satisfaction, illness cognitions), ANS measurements were then recorded of them at rest, during completion of a mental task (reactivity), and while in recovery following this task. The first 24-day period was a control period without any practice, and the second was an intervention period with HRV-BFB. Participants practiced HRV-BFB daily for 5 min, three times a day, for 24 days. We found that HRV-BFB reduced psychological distress and the feeling of helplessness, and led to a decrease in sympathetic reactivity during the mental task. Our findings support the potential relevance of HRV-BFB to manage mental health in adults with IBS.

Gastric feelings are often studied using invasive stimulations changing the stomach state and overlooking how context and personality traits shape these sensations. Therefore, we developed a virtual reality protocol to modulate gastric feelings through embodiment and anxiety manipulations. Twenty-eight healthy women experienced stimulation of a virtual abdomen synchronized or not with tactile stimulation on their own abdomen. Different levels of threat were induced by approaching a syringe or spoon toward the virtual belly. Results showed that embodiment and threat increased the intensity and unpleasantness of gastric feelings and enhanced their visceral nature. Exploratory analyses revealed that higher somatic sensitivity, interoceptive concern, and alexithymia were associated with more intense, unpleasant, and visceral gastric feelings. This proof-of-concept study proposes a non-invasive immersive protocol for investigating gastric feelings in women across clinical and healthy populations at a larger scale.

Both cognitive motor dual-tasks (CMDT) protocols and hypoxic environments have been associated with significant impairments in cognitive and physical performance. We aimed to determine the effects of hypoxia on cognitive performance and neuromuscular fatigue during a highly physically demanding CMDT. Fifteen young adults completed a first session involving a cognitive task (CTLCOG) followed by cycling exercise (CTLEX) in normoxia. After that, they randomly participated in CMDT sessions in normoxia (DTNOR) and hypoxia (DTHYP). The physical exercise consisted of 20 min cycling at a “hard” perceived effort, and the cognitive task consisted of 15 min sustained attention to response time task (SART). Concurrent psycho-physiological measurements included: quadriceps neuromuscular fatigue (peripheral/central components from femoral nerve electrostimulation), prefrontal cortex (PFC) oxygenation by near-infrared spectroscopy, and perception of effort. SART performance significantly decreased in DTNOR (-15.7 ± 15.6

A positivity effect in attention (i.e., an attentional bias in favor of positive over negative stimuli) has been frequently reported in older adults. Based on the postulates of socioemotional selectivity theory (SST), the present study tested whether this positivity effect: (a) depends on the subjective perception of a limited future time perspective (FTP) independently of chronological age, (b) involves controlled processes, and (c) contributes to optimizing positive emotions. Thirty-one older adults (aged 75-93) and 92 younger adults (aged 18-23) were recruited. Young adults were divided into a control group (N = 52) and a group with limited FTP (N = 40), where their subjective perception of the time left to live was experimentally reduced. All participants performed a dot-probe task involving positive, negative and neutral pictures displayed with different presentation durations (500 ms, 1,000 ms). Reaction time bias scores were calculated, and emotional state was measured several times during the task. Analyses revealed attentional biases toward positive (compared to negative) pictures in older adults and young adults with limited FTP, but not in young adults in the control group. These positivity effects appeared from 500 ms of stimulus presentation, did not increase over time, and did not correlate with participants' emotions. These findings support SST predictions that positivity effects occur when individuals perceive a limited FTP, regardless of their actual age. However, our data also suggest that the positivity effect may be a more automatic than controlled process that does not influence emotional state.

The characteristics of a natural positive cloud-to-ground lightning flash which had only one return stroke are investigated in detail using synchronous detections of lightning very-high-frequency (VHF) interferometer, fast antenna, high-speed video and S-band Doppler weather radar. The flash initiated at 5.8 km above the ground and at the edge of an enhancing convective cell, where a positive bi-level charge structure was involved. The initial negative leader developed upward, forming multiple branches, while the positive leader was recognized 22.2 ms later. The breakdown with different polarities exhibited distinct properties. Three significant negative breakdowns initiating in the previously established but extinguished negative channels were well detected by the VHF interferometer, with a duration of 0.30 ms, 0.06 ms and 0.20 ms, and propagation speed of 1.9 × 106 m/s, 2.2 × 107 m/s and 1.9 × 107 m/s, respectively. The first one occurred 0.3 ms before the return stroke, its occurrence promoted the development of the downward positive leader that was getting close to the ground, leading to an obvious acceleration and an enhancement of the channel luminosity. The second and the third negative breakdowns occurred during the continuing current after the return stroke, acting as the causation of the positive M-components. Symmetric V-shaped and hooked pulses on the fast electric field change waveform and obvious increased luminosity of the grounded channel were well detected. The occurrence of negative breakdowns in the pre-conditioned channels served for producing a backward surged current wave that promote the discharge process through the grounding/grounded channel.

Climate change has been deemed the biggest global health threat of the 21st century. One consequence of climate change is the increasing frequency and severity of forest fires. Smoke from wildfires has the ability to negatively impact air quality over large distances. The aim of this study was to examine the association that air quality had on emergency department visits for cardiac, respiratory and psychiatric/behavioral health chief complaints during forest fire season in Vancouver, British Columbia.The study period was January 1, 2009 – December 31, 2019. Forest fire season was defined as April 1- September 30. Air quality (measured by PM2.5 in ug/m3) was obtained from the Vancouver International Airport (YVR) Air Quality station. Emergency department visit data (CEDIS triage complaint) was acquired from a regional emergency department database. A generalized linear mixed model with Poisson link function was used to determine the relative risk (as a percentage) for respiratory, cardiac and psychiatric/behavioral health CEDIS triage complaints associated with a 10 unit increase in PM2.5.PM2.5 during forest fire season was significantly associated with emergency department visits for respiratory chief complaints. For every 10 ug/m3 increase in PM2.5, there was a 4.61% (95% CI: 3.07, 6.17) increase in relative risk of respiratory chief complaints presenting to emergency departments. No association was found between PM2.5 and cardiac or psychiatric/behavioral health chief complaints during forest fire season or non-forest fire season. During non-forest fire season, PM2.5 was found to be negatively associated with respiratory (-3.57, 95% CI: -5.44, -1.66) and cardiac chief complaints (-2.77, 95% CI: -4.16, -1.47).Our results indicate a probable association between air quality during forest fire season and emergency department visits for respiratory chief complaints. This provides further illustration of the widespread impact of climate change, and underscores the importance of efforts to address it.

Background Functional neurological disorders (FND), a subtype of functional disorders (FD), are a frequent motive for neurology referrals. The various presentations and the unknown physiopathology of FD have led to the multiplication of terms describing these disorders over the years. Methods We examined the FD-related articles published from 1960 to 2020 in PubMed and PsycINFO databases. We searched for: psychogenic, somatization, somatoform, medically unexplained symptoms, hysteria, conversion disorder, dissociative, functional neurological disorder, and functional disorder . Use rates in the title, abstract, keyword, or MeSH fields were collected over successive 5-year periods. After correcting for off-topic results, we examined proportional distribution over time, term associations, and disciplinary fields (neurology and psychiatry). Term impact was estimated via H-index and number of citations. Results We found that none of the terms is prevailing in the recent medical literature. We observed three trends in the use rates: stability, increase, and decrease of use over time. While most of the terms were present in a stable proportion of the publications, hysteria and psychogenic lost popularity over time. We found a differential preference for terminology between disciplines. Functional neurological disorder showed the highest citation impact, yielding 10% of highly cited publications. Conclusion We found a dynamic and evolving use of the different terms describing FD in the last 60 years. Despite the tendency to use the term functional in the recent highly cited publications, its low prevalence and coexistence with several other terms suggest that a precise, explanatory and non-offensive term remains yet to be found.

The hippocampus is usually associated with recall memory, whereas its contribution to familiarity-based memory is debated. Growing evidence support the idea that this structure participates to any cognitive process performed on scene representations. In parallel, differences in functional specialisation and cortical connectivity were found across the longitudinal and transverse axes of the hippocampus. Here we reanalysed functional MRI data from 51 participants showing stronger engagement of the hippocampus in recall, familiarity-based recognition and rejection, and visual discrimination, of scenes compared to single objects. A conjunction analysis between these four tasks revealed a set of occipital, medial temporal, posterior cingulate, and parietal regions, matching the scene construction network described in the literature. Crucially, we found that the anterior medial part of the hippocampus was consistently involved in all tasks investigated for scene stimuli. These findings support that the hippocampus can contribute to both recall and familiarity-based memory, depending on stimulus type. More generally, this bolsters the recent proposal that circumscribed regions within the hippocampus may underpin specific cognitive mechanisms.

The prevailing view in human cognitive neuroscience associates the medial temporal lobes (MTLs) with declarative memory. Compelling experimental evidence has, however, demonstrated that these regions are specialized according to the representations processed, irrespective of the cognitive domain assessed. This account was supported by the study of patients with bilateral medial temporal amnesia, who exhibit impairments in perceptual tasks involving complex visual stimuli. Yet, little is known regarding the impact of unilateral MTL damage on complex visual abilities. To address this issue, we administered a visual matching task to 20 patients who underwent left (N = 12) or right (N = 8) anterior temporal lobectomy for drug-resistant epilepsy and to 38 healthy controls. Presentation viewpoint was manipulated to increase feature ambiguity, as this is critical to reveal impairments in perceptual tasks. Similar to control participants, patients with left-sided damage succeeded in all task conditions. In contrast, patients with right-sided damage had decreased accuracy compared with that of the other two groups, as well as increased response time. Notably, the accuracy of those with right-sided damage did not exceed chance level when feature ambiguity was high (i.e., when stimuli were presented from different viewpoints) for the most complex classes of stimuli (i.e., scenes and buildings, compared with single objects). The pattern reported in bilateral patients in previous studies was therefore reproduced in patients with right, but not left, resection. These results suggest that the complex visual-representation functions supported by the MTL are right-lateralized, and raise the question as to how the representational account of these regions applies to representations supported by left MTL regions.

The aim of this study was to evaluate the prevalence of early life stress (ELS) in a population with inflammatory bowel diseases (IBD) and to estimate its burden on mental, physical, and digestive health. Ninety-three participants with IBD were asked to anonymously complete questionnaires (Childhood Trauma Questionnaire-Short Form, Early Life Event Scale, Perceived Stress Scale, Hospital Anxiety and Depression Scale, Ways of Coping Checklist, Gastro-Intestinal Quality of Life Index questionnaire, and ad hoc questions about symptoms). The prevalence of patients with IBD who were exposed to at least one childhood abuse was 53%. Mental health and quality of life were significantly poorer in patients with IBD who were exposed to early abuse than in those who were not. Patients exposed to ELS had also more digestive perturbations and fatigue. These results suggest that early abuse should be considered a component of IBD care.