Desynchronization Of Rhythms Research Articles

Neurophysiological Oscillatory Mechanisms Underlying the Effect of Mirror Visual Feedback-Induced Illusion of Hand Movements on Nociception and Cortical Activation.

Mirror Visual Feedback (MVF)-induced illusion of hand movements produces beneficial effects in patients with chronic pain. However, neurophysiological mechanisms underlying these effects are poorly known. In this preliminary study, we test the novel hypothesis that such an MVF-induced movement illusion may exert its effects by changing the activity in midline cortical areas associated with pain processing. Electrical stimuli with individually fixed intensity were applied to the left hand of healthy adults to produce painful and non-painful sensations during unilateral right-hand movements with such an MVF illusion and right and bilateral hand movements without MVF. During these events, electroencephalographic (EEG) activity was recorded from 64 scalp electrodes. Event-related desynchronization (ERD) of EEG alpha rhythms (8-12 Hz) indexed the neurophysiological oscillatory mechanisms inducing cortical activation. Compared to the painful sensations, the non-painful sensations were specifically characterized by (1) lower alpha ERD estimated in the cortical midline, angular gyrus, and lateral parietal regions during the experimental condition with MVF and (2) higher alpha ERD estimated in the lateral prefrontal and parietal regions during the control conditions without MVF. These preliminary results suggest that the MVF-induced movement illusion may affect nociception and neurophysiological oscillatory mechanisms, reducing the activation in cortical limbic and default mode regions.

The Role of the Motor System in L1 and L2 Action Verb Processing for Chinese Learners of English: Evidence from Mu Rhythm Desynchronization.

The nature of semantic representation has long been a key question in linguistic research. The Embodied Cognition theory challenges the traditional view of language representation, stating that semantic information stems from the sensory-motor cortex, which is activated automatically during semantic processing. However, most of the evidence comes from monolingual studies; it remains unclear whether second-language (L2) comprehension involves different semantic representations or mirrors the pattern seen in first-language (L1) processing. Therefore, the present study investigated the role of the sensory-motor system in language processing via making Electroencephalography (EEG) recordings during the processing of L1 and L2 action verbs. The results showed that L1 (Chinese) action verbs generated higher mu-event-related desynchronization (ERD) than L1 abstract verbs in the early processing stage (250 ms after verb presentation), and the same phenomenon was also observed for L2 (English). The results also indicated that language modulated the processing of action verbs, with L1 action verbs eliciting stronger ERD than L2 action verbs. These results demonstrate that the sensory-motor cortex plays a crucial role in comprehending both L1 and L2 action verbs.

Chronicles of the midnight strain: Exploring graveyard shift stress and its impact on employee burnout in call centers

This study, titled “Chronicles of the Midnight Strain: Exploring Graveyard Shift Stress and Its Impact on Employee Burnout in Call Centers,” delves into the intricate relationship between the demanding nature of graveyard shift work in call centers and its potential consequences on employee burnout. The research adopts a comprehensive approach, investigating various factors such as electronic performance monitoring, job demands, physiological indicators, and the role of lifestyle factors in cardiovascular health. Drawing from a vast array of literature, the study explores the causal links and mechanisms of action, emphasizing the significant role of sleep disruption and circadian rhythm desynchronization in contributing to cardiovascular disease among shift workers. Additionally, it considers the impact of stress, working hours, and dietary patterns on the overall well- being of employees working during the unconventional hours of the night. The study reviews existing theories proposing connections between shiftwork, sleep loss, and cardiovascular diseases. It scrutinizes factors like inflammation, blood coagulation, cardiac autonomic function, and the interplay between stress-related hormones and cardiovascular health. Multiple hypotheses are examined, including the influence of a stressful work environment, disturbed sleep on the immune system, and lifestyle factors such as dietary habits and substance use. Despite over two decades of continuous research, the findings in this area remain inconclusive regarding the precise role of shiftwork in cardiovascular disease. The study aims to contribute valuable insights into mitigating the potential adverse effects of graveyard shift stress on employee burnout in call centers, providing a foundation for further research and the development of targeted interventions.

Circadian epidemiology: Structuring circadian causes of disease and practical implications

ABSTRACT That disruptions of the body’s internal clockwork can lead to negative health consequences, including cancer, is a plausible hypothesis. Yet, despite strong mechanistic and animal support, the International Agency for Research on Cancer (IARC) experts considered epidemiological evidence as limited regarding the carcinogenicity of “shift-work involving circadian disruption” (2007) and “night shift work” (2019). We use directed acyclic graphs (DAGs) to outline a concept of circadian causes that discloses challenges when choosing appropriate exposure variables. On this basis, we propose to move beyond shift-work alone as a direct cause of disease. Instead, quantifying chronodisruption as individual doses can lead to interpretable circadian epidemiology. The hypothesis is that doses of chronodisruption cause disrupted circadian organisation by leading to desynchronization of circadian rhythms. Chronodisruption can be conceptualized as the split physiological nexus of internal and external times. Biological (or internal) night – an individual’s intrinsically favoured sleep time window – could be the backbone of circadian epidemiology. In practice, individual doses that cause disrupted circadian organisation are derived from the intersection of time intervals of being awake and an individual’s biological night. After numerous studies counted work shifts, chronobiology may now advance circadian epidemiology with more specific dose estimation – albeit with greater challenges in measurement (time-dependent individual data) and analysis (time-dependent confounding).

Prospective comparative analysis of the ambulatory blood pressure monitoring changes in patients with hypertension after COVID‑19 in the conditions of the Arctic watch

Objective. To conduct a prospective (2-year) comparative analysis of the dynamics of 24-hour ambulatory blood pressure monitoring (ABPM) in patients with arterial hypertension (HTN) and previous COVID-19 infection working in the conditions of the Arctic watch.Design and methods. In the Medical Unit of Gazprom Dobycha Yamburg LLC (GDY) in the polar shift settlement of Yamburg, 347 patients were examined: 222 men (M) and 125 women (W). All of them underwent ABPM according to the standard protocol in 2019 and 2022. Among them, 261 patients had confirmed COVID-19 between 2020 and 2021 and were treated in the Medical Unit of GDY. Among the examined M and W, according to medical history in 2019, 80 % of M (178 from 222 people) and 66 % of W (82 from 125 people) had elevated blood pressure (BP), p = 0,003. Among patients with HTN, 109 M (61,2 %) and 42 W (51,2 %) survived after COVID-19, p = 0,129. They formed observation group (n = 151). Comparison group included HTN patients without COVID-19 (n = 109).Results. In patients with HTN who had COVID-19, ABPM showed an increase in average daily systolic BP (SBP) values after 2 years: from 134,5 (12,3) to 140,5 (11,8) mmHg (p < 0,0001) and diastolic BP (DBP): from 96,6 (14,0) to 105,1 (13,4) mmHg (p < 0,0001), hypertensive load time indices (TI): TI SBP24 (from 49,5 (29,3) to 61,6 (28,1) mmHg (p < 0,0001) and TI DBP24 from 69,3 (30,5) to 83,4 (21,9) mmHg (p < 0,0001), increase in daytime SBP variability (p = 0,048), decrease in daily SBP indices by 1,2 %: from 7,9 (4,6) to 6,7 (4,3) (p = 0,038) and DBP by 2,0 %: from 9,7 (4,8) to 7,7 (4,7) (p = 0,032). Desynchronization of SBP and DBP rhythms were found by chronobiological analysis.Conclusions. A prospective comparative analysis of the dynamics of ABPM in patients with HTN after COVID-19 in the conditions of the Arctic watch showed an increase in the average daily values of SBP and DBP and their daily variability, deterioration in the daily BP profile with an increase in the “night peaker” phenotype. In patients with HTN who did not have COVID-19, a prospective analysis of ABPM showed a significant increase in DBP and average daily hypertensive load of DBP, which may contribute to further cardiovascular remodeling. In patients with HTN who have recovered from COVID-19, desynchronization processes of SBP and DBP rhythms intensify, which requires an in-depth analysis of the chronobiological structure of the rhythm BP.

Brief Visual Deprivation Effects on Brain Oscillations During Kinesthetic and Visual-motor Imagery.

It is widely recognized that opening and closing the eyes can direct attention to external or internal stimuli processing. This has been confirmed by studies showing the effects of changes in visual stimulation changes on cerebral activity during different tasks, e.g., motor imagery and execution. However, an essential aspect of creating a mental representation of motion, such as imagery perspective, has not yet been investigated in the present context. Our study aimed to verify the effect of brief visual deprivation (under eyes open [EO] and eyes closed [EC] conditions) on brain wave oscillations and behavioral performance during kinesthetic imagery (KMI) and visual-motor imagery (VMI) tasks. We focused on the alpha and beta rhythms from visual- and motor-related EEG activity sources. Additionally, we used machine learning algorithms to establish whether the registered differences in brain oscillations might affect motor imagery brain-computer interface (MI-BCI) performance. The results showed that the occipital areas in the EC condition presented significantly stronger desynchronization during VMI tasks, which is typical for enhanced visual stimuli processing. Furthermore, the stronger desynchronization of alpha rhythms from motor areas in the EO, than EC condition confirmed previous effects obtained during real movements. It was also found that simulating movement under EC/EO conditions affected signal classification accuracy, which has practical implications for MI-BCI effectiveness. These findings suggest that shifting processing toward external or internal stimuli modulates brain rhythm oscillations associated with different perspectives on the mental representation of movement.

Feeding during the resting phase causes gastrointestinal tract dysfunction and desynchronization of metabolic and neuronal rhythms in rats.

Disrupted circadian rhythms may result from a misalignment between the environmental cycles (due to shift work, sleep restriction, feeding at an unusual time of day) and endogenous rhythms or by physiological aging. Among the numerous adverse effects, disrupted rhythms affect the brain-gut axis, contributing to the pathogenesis of several diseases in the gastrointestinal tract, for example, abdominal pain, constipation, gastric dyspepsia, inflammatory bowel disease, irritable bowel syndrome, and others. This study evaluated the rat gastric emptying, gastrointestinal motility, a clock gene, gut hormones, and the neuron activity on the nucleus of tractus solitarius (NTS), area postrema (AP), and the dorsal motor nucleus of the vagus (DMV) in rats with restricted food access to the rest phase for 4 weeks. Our results show that food restricted to the rest light period disturbed the expression pattern of a series of transcripts, including metabolic and circadian regulation. Also, the secretion of gastrointestinal hormones, gastric emptying, intestinal motility, and NTS, AP, and DMV activity were altered. These data indicate the importance of the time of the day food is ingested on the regulation of energy balance and the endocrine activity of the stomach and small intestine, emphasizing the importance of food as a powerful circadian synchronizer and an essential factor for the triggering of gastrointestinal diseases and metabolic problems. These findings offer a novel clue regarding the obesity-promoting effect attributed to feeding time and open the possibility of treating this and other intestinal disorders.

Chronic jet lag reduces motivation and affects other mood-related behaviors in male mice.

Introduction: The circadian system regulates various physiological processes such as sleep-wake cycles, hormone secretion, metabolism, and the reaction to both natural and drug-based rewards. Chronic disruption of the circadian system caused by unsteady synchronization with light-dark (LD) schedules, such as advancing chronic jet lag (CJL), leads to adverse physiological effects and pathologies, and is linked with changes in mood and depressive behaviors in humans and rodent models. Methods: C57BL/6J male mice were subjected to circadian disruption through phase advances of 6h every 2days (CJL +6/2). Mice under 12:12-h LD cycle were used as controls. After 8weeks under these conditions, a battery of behavioral tests was performed to assess if mood-related behaviors were affected. Results: Compared to controls under 24h LD cycles, mice under CJL presented desynchronization of activity-rest rhythms that led to several behavioral impairments, including a decrease in motivation for food reward, and an increase in anxiety, anhedonia, and depressive-like behavior. Conclusion: Chronic circadian disruption, caused by an experimental CJL protocol, affects mood-related and reward-related behaviors in mice. Understanding the importance of the circadian system and its potential role for disruption due to CJL is important for maintaining good health and well-being.

Familiarity of Brazilian psychologists with basic concepts in sleep science and chronobiology

ABSTRACT Desynchronization of circadian rhythms and sleep-wake patterns impacts biochemical, physiological, and behavioral functions, including mental processes. The complex relationship between circadian rhythms and mental health makes it challenging to determine causality between circadian desynchronization and mental disorders. Regarding the fact that psychologists act as the front line for initial mental health care, we aimed to assess the knowledge and use of sleep science and basic chronobiology by professional psychologists in Brazil. Data were collected via an online questionnaire completed by 1384 professional psychologists between October 2018 and May 2019. Our findings revealed that ±80% of psychologists reported that at least half of their patients presented some sleep-related complaints; however, only ±27% routinely inquired about sleep quality even in the absence of patient complaints. Additionally, only ±66% initiated treatments to understand these complaints, potentially influenced by the lack of prior academic exposure to biological rhythms as reported by ±76% of Brazilian psychologists interviewed. Importantly, ±15% did not believe in an association between mental health and biological rhythms, and even a significant ±67% were unfamiliar with the term chronobiology and ±63% were not able to describe any other biological rhythm except for the sleep-wake cycle. These results demonstrate that fundamental concepts in chronobiology and sleep science are unknown to a substantial proportion of Brazilian psychologists. In conclusion, we propose that this subject could be more effectively integrated into psychologists’ academic training, potentially promoting benefits through the incorporation of a chronobiological approach in mental health practice.

From gestational chronodisruption to noncommunicable diseases: Pathophysiological mechanisms of programming of adult diseases, and the potential therapeutic role of melatonin.

During gestation, the developing fetus relies on precise maternal circadian signals for optimal growth and preparation for extrauterine life. These signals regulate the daily delivery of oxygen, nutrients, hormones, and other biophysical factors while synchronizing fetal rhythms with the external photoperiod. However, modern lifestyle factors such as light pollution and shift work can induce gestational chronodisruption, leading to the desynchronization of maternal and fetal circadian rhythms. Such disruptions have been associated with adverse effects on cardiovascular, neurodevelopmental, metabolic, and endocrine functions in the fetus, increasing the susceptibility to noncommunicable diseases (NCDs) in adult life. This aligns with the Developmental Origins of Health and Diseasetheory, suggesting that early-life exposures can significantly influence health outcomes later in life. The consequences of gestational chronodisruption also extend into adulthood. Environmental factors like diet and stress can exacerbate the adverse effects of these disruptions, underscoring the importance of maintaining a healthy circadian rhythm across the lifespan to prevent NCDs and mitigate the impact of gestational chronodisruption on aging. Research efforts are currently aimed at identifying potential interventions to prevent or mitigate the effects of gestational chronodisruption. Melatonin supplementation during pregnancy emerges as a promising intervention, although further investigation is required to fully understand the precise mechanisms involved and to develop effective strategies for promoting health and preventing NCDs in individuals affected by gestational chronodisruption.

Le sommeil d’un performeur de l’extrême. Dormir huit jours et sept nuits, assis, sans bouger, enfermé dans une sculpture

Sleep in extreme situations has been little studied. The artist Abraham Poincheval (AP) is known for his performances in confined spaces. For his show at the Perrotin Gallery in Paris, he was enclosed for 8days and 7nights in a metal sculpture of his body in a seated position, with his head facing a work by Hans Hartung at the end of a cone system placed in front of his eyes which occluded all other visual stimuli. The interior of the metal structure was not padded and there was no head support. His sleep and internal temperature were continuously recorded using polysomnography (Grael, Compumedics) and an orally swallowed temperature sensitive capsule (Bodycap) with temperature sampling every 2min. AP slept an average of 355.1min/24h, composed of light slow-wave sleep (N1: 47.1min, N2: 192.2min), deep slow-wave sleep (N3: 100.4min), and REM sleep 4,3 % (15.4min). Sleep, although mostly nocturnal, was split into periods of no more than 20min. Deep sleep was therefore remarkably resistant to the uncomfortable experimental conditions, while REM sleep was markedly impaired, lasting only a few short minutes and followed by rapid awakening. This is probably due to the head position within the sculpture which was unsupported, so REM sleep with its inherent muscle atonia led to involuntary head flexion and was impossible to sustain for long. The thermal minimum was between 5:17 a.m. and 6:35 a.m. The amplitude of the core temperature decreased by more than 30 % between the beginning and the end of the protocol. Despite the immobility induced by the confined experimental conditions, there was no desynchronization of circadian rhythms. The sleep time was surprisingly long given the conditions, and slow-wave sleep was relatively preserved with an amount typically found in normal subjects while REM sleep was markedly impaired. Slow-wave sleep is clearly preserved underlying its central role in physical and mental homeostasis. REM sleep is clearly more fragile. The reduction in REM sleep linked to position has been found in a study of sleep in the sitting position in airplanes where loss of muscle tonus in the neck fragments REM sleep. Techniques for selective REM sleep deprivation also use muscle atonia: one of the initial techniques of selective REM sleep deprivation relied on muscle atonia in REM causing a cat to fall from a small perch into water. In man, the lack of head support is clearly a source of REM fragmentation. However in the case of this study, we cannot exclude an effect of other factors, notably the meditative techniques used by the performer to maintain attention on the painting, described as a dream state punctuated by visual hallucinations. Surprisingly, despite physical isolation within the sculpture, AP's biological rhythms remained stable. However, the conditions were not those of complete isolation: noise, the presence of the public in the gallery who occasionally talked to AP through the sculpture, and variations in light during the day were all temporal cues. In addition, a heatwave during the performance raised the temperature in the room with reduced total sleep time on the hottest night. Although the phase of the circadian rhythm measured by the internal temperature did not change, the amplitude fell which is compatible with reduced physical activity. In conclusion, under physically constraining and uncomfortable sleep conditions, deep sleep is maintained while REM sleep is starkly reduced. From a homeostatic point of view, this means that over a short period of time, in a survival situation, energy recovery through deep slow-wave sleep takes priority over REM sleep.

Possible disrupted biological movement processing in Developmental Coordination Disorder

AimThere is emerging evidence that the Mirror Neuron System (MNS) might contribute to the motor learning difficulties characteristic of Developmental Coordination Disorder (DCD). This study aimed to identify whether MNS activity differed between children with and without DCD during action observation, action execution and during a non-action baseline. MethodsElectroencephalography (EEG) was used to measure mu rhythm (a proxy for MNS activation) in 8-12-year-old children either with (n = 20) or without (n = 19) a diagnosis of DCD. The mu rhythm was recorded at rest and during five experimental conditions: (1) observation of gross motor and (2) fine motor actions; (3) execution of gross motor and (4) fine motor actions; and (5) non-biological movement. To address whether potential co-occurring traits of other neurodevelopmental conditions were associated with differences in mu rhythm, parents reported their child's attention and social communication skills. Mixed and repeated measure ANOVAs were conducted to examine differences in mu desynchronization and mu power respectively. ResultsThe non-DCD group showed greater mu rhythm desynchronization than children with DCD (i.e., more MNS activity), with both groups demonstrating increasing desynchronization from observation of fine actions to execution of gross actions. However, we also found that the children with DCD had less mu power during the non-biological movement condition than the non-DCD children, although mu power did not differ between groups during the resting condition. Correlations between mu desynchronization and children's attention and motor skills showed that poorer attention and motor abilities were associated with reduced MNS activity. ConclusionCompared to children without DCD, the MNS in children with DCD did not distinguish between biological and non-biological movement. It is possible that the reduced specificity of the MNS in children with DCD is an underlying factor in the motor impairments observed in the disorder. The differential MNS activity could reflect broader atypical activity in perceptual networks that feed into the MNS in DCD.

DYNAMICS OF THE EEG SENSORIMOTOR RHYTHM DURING MENTAL REPETITION OF THE OBSERVED MOVEMENT

Mental simulation of one’s own movement, or imagery of movement, as well as observation of other people’s movements are used in neurorehabilitation as methods of stimulation of sensorimotor parts of the brain. The present work tests a new way of representation - mental simulation of movement, synchronous with the movement observed from the first person on a video screen. The objectives of the study were to compare the reactivity of sensorimotor EEG rhythms during voluntary movement representation and representation following a video stimulus, and to identify the relationship between the phases of movement in the video and the dynamics of EEG patterns. The study involved 30 healthy volunteers in whom a 69-channel encephalogram was recorded during their performance and presentation of right thumb movements in two modes: arbitrarily (without an external reference) and synchronously imitating movement on a video clip. During EEG analysis, individual spatial-frequency components with the highest EEG mu-rhythm reactivity (8–14 Hz) were identified in the subjects, followed by quantitative assessment of desynchronization under the studied conditions based on analysis of probability density distributions of mu-rhythm power. A generalized additive model describing the function of responses to single events in the observed movements and their summation during serial execution or presentation of the movements was applied to assess the relationship between the dynamics of mu-rhythm desynchronization and video events. It was shown that the mental kinesthetic simulation of the observed movement did not result in increased desynchronization of sensorimotor rhythms compared to the voluntary representation of the same movement. It was found for the first time that there are perturbations in the temporal course of desynchronization of the mu-rhythm that depend on the phase and speed of the observed movement both during its synchronous muscle repetition and during mental synchronous imitation. The results obtained can be used to optimize movement parameters in individual systems of ideomotor training with EEG control to achieve the greatest sensorimotor activation.

Beyond passive observation: feedback anticipation and observation activate the mirror system in virtual finger movement control via P300-BCI.

Action observation (AO) is widely used as a post-stroke therapy to activate sensorimotor circuits through the mirror neuron system. However, passive observation is often considered to be less effective and less interactive than goal-directed movement observation, leading to the suggestion that observation of goal-directed actions may have stronger therapeutic potential, as goal-directed AO has been shown to activate mechanisms for monitoring action errors. Some studies have also suggested the use of AO as a form of Brain-computer interface (BCI) feedback. In this study, we investigated the potential for observation of virtual hand movements within a P300-based BCI as a feedback system to activate the mirror neuron system. We also explored the role of feedback anticipation and estimation mechanisms during movement observation. Twenty healthy subjects participated in the study. We analyzed event-related desynchronization and synchronization (ERD/S) of sensorimotor EEG rhythms and Error-related potentials (ErrPs) during observation of virtual hand finger flexion presented as feedback in the P300-BCI loop and compared the dynamics of ERD/S and ErrPs during observation of correct feedback and errors. We also analyzed these EEG markers during passive AO under two conditions: when subjects anticipated the action demonstration and when the action was unexpected. A pre-action mu-ERD was found both before passive AO and during action anticipation within the BCI loop. Furthermore, a significant increase in beta-ERS was found during AO within incorrect BCI feedback trials. We suggest that the BCI feedback may exaggerate the passive-AO effect, as it engages feedback anticipation and estimation mechanisms as well as movement error monitoring simultaneously. The results of this study provide insights into the potential of P300-BCI with AO-feedback as a tool for neurorehabilitation.

Increased sensitivity of spatial filters by combining the magnetic and electrical components of the sensorimotor cortical beta rhythm

Modulation of human magnetic or electrical sensorimotor rhythms during motor imagery is widely used in fundamental and applied neurophysiological research. To date, there is evidence of a better sensitivity of magnetic field sensors to beta-rhythm modulation, however, the potential synergistic effect of combining the two modalities has not yet been investigated. In this study, simultaneous registration of electroencephalogram (EEG) and magnetoencephalogram (MEG) was carried out in eight healthy volunteers during voluntary and imaginary movements, as well as during electrical stimulation of the median nerve. In all subjects, it was possible to identify desynchronization (suppression) of mu and beta rhythms during the performance of sensorimotor tasks, as well as beta synchronization after the end of movement or stimulation. Using the common projections of the covariance matrices of signals of the electric, magnetic, and combined (“MEEG”) modalities, the most sensitive individual spatial filters were calculated separately for each type of reaction. Relative to the pre-stimulus control, the changes in the amplitude of the sensorimotor rhythm components turned out to be the largest in the combined MEEG modality. At the same time, for mu-desynchronization, MEEG turned out to be significantly better than MEG, and for beta-desynchronization, MEEG turned out to be significantly better than both MEG and EEG. For beta synchronization, a shift in the position of sources in the fronto-medial direction was shown, and there were no significant differences in amplitude between modalities. It was also shown that for beta desynchronization, most subjects identified MEG sources with identical EEG projections or without pronounced EEG projections, which indicates the presence of several small tangentially located cortical dipoles involved in beta rhythm desynchronization. The results obtained indicate that in studies of modulation of sensorimotor rhythm components, in particular beta desynchronization, the combination of MEG and EEG leads to greater sensitivity. The multifocal nature of the magnetic beta rhythm and its varying severity in EEG sources indicate the presence of independent regulatory circuits of cortical-thalamic or intracortical origin.

Congruent action context releases Mu rhythm desynchronization when visual objects activate competing action representations.

Recent findings demonstrated that object perception is affected by the competition between action representations. Simultaneous activation of distinct structural ("grasp-to-move") and functional ("grasp-to-use") action representations slows down perceptual judgements on objects. At the brain level, competition reduces motor resonance effects during manipulable object perception, reflected by an extinction of μ rhythm desynchronization. However, how this competition is solved in the absence of object-directed action remains unclear. The present study investigates the role of context in the resolution of the competition between conflicting action representations during mere object perception. To this aim, thirty-eight volunteers were instructed to perform a reachability judgment task on 3D objects presented at different distances in a virtual environment. Objects were conflictual objects associated with distinct structural and functional action representations. Verbs were used to provide a neutral or congruent action context prior or after object presentation. Neurophysiological correlates of the competition between action representation were recorded using EEG. The main result showed a release of μ rhythm desynchronization when reachable conflictual objects were presented with a congruent action context. Context influenced μ rhythm desynchronization when the action context was provided prior or after object presentation in a time-window compatible with object-context integration (around 1000ms after the presentation of the first stimulus). These findings revealed that action context biases competition between co-activated action representations during mere object perception and demonstrated that μ rhythm desynchronization may be an index of activation but also competition between action representations in perception.

Long-term artificial/natural daytime light affects mood, melatonin, corticosterone, and gut microbiota in rats

The desynchronization of circadian rhythms affected by light may induce physiological and psychological disequilibrium. We aimed to elucidate changes of growth, depression-anxiety like behaviors, melatonin and corticosterone (CORT) secretion, and gut microbiota in rats influenced by long-term light inputs. Thirty male Sprague-Dawley rats were exposed to a 16/8h light/dark regime for 8weeks. The light period was set to 13h of daylight with artificial light (AL group, n = 10), or with natural light (NL group, n = 10), or with mixed artificial-natural light (ANL group, n = 10), and 3h of artificial night light after sunset. The obtained findings indicated that the highest weight gain and food efficiency were observed in the AL group and the lowest in NL group. In the behavioral tests, the NL and ANL groups showed lower anxiety level than AL group, and ANL groups showed lower depression level than AL group. The NL and ANL groups had delayed acrophases and maintained higher concentrations of melatonin compared to AL group. The circadian rhythm of CORT was only found in ANL group. At the phylum level, the mixed light contributed to a lower abundance of Bacteroidetes. The genus level results recommend a synergistic effect of artificial light and natural light on Lactobacillus abundance and an antagonistic effect on the Lachnospiraceae_NK4A136_group abundance. The study indicated that the mixture of artificial and natural light as well as the alignment of the proportions had beneficial influences on depression-anxiety-like levels, melatonin and corticosterone secretion, and the composition of the gut microbiota. KEY POINTS: • The mixed light can reduce the depression-anxiety level • The mixed light can maintain the secretion rhythm of melatonin and CORT • The mixed light can increase Lactobacillus and decrease Lachnospiraceae_NK4A136_group.

Особенности реактивности μ-ритма ЭЭГ у детей с расстройствами аутистического спектра в ситуациях помогающего поведения

One of the subjects being discussed by the professional community currently is the role possibly played by the mirror neuron system (MNS) in the violation of social behavior of children with autism spectrum disorders (ASD). The MNS is known to shape the perception of emotions of others and understanding and imitation of their actions. Mu rhythm desynchronization in EEG is considered to be the indicator of the MNS activation. The purpose of this study was to identify the features of reactivity of the EEG mu rhythm within an individually determined frequency range in preschoolers with ASD in situations requiring instrumental, emotional and altruistic helping behavior (HB). The study involved children 4–7 years old with ASD (n = 26) and their normally developing peers without the condition (n = 37). Although in most cases, HB was more pronounced in the group of normally developing children, the differences between the groups are significant only for altruistic HP (p < 0.01), and for the situation requiring complex altruistic and emotional HP it approaches significance (p = 0.09). Evaluation of the mu rhythm reactivity indices showed that the tasks invoking complex altruistic and emotional HB bring this indicator down significantly in children with ASD compared to the group of normally developing participants, as shown by the central leads of the left and right hemispheres and the parietal lead of the right hemisphere (C3: p = 0.02 ; C4: p = 0.03; P4: p = 0.03). It is assumed that the detected features stem from the impaired functioning of the MNS and the downstream regulation to the MNS from prefrontal cortex and other areas of the neocortex. The data obtained can be used in development of EEG biofeedback training protocols for children with ASD.

Quasi-Movements and “Quasi-Quasi-Movements”: Does Residual Muscle Activation Matter?

Quasi-movements (QM) are observed when an individual minimizes a movement to an extent that no related muscle activation is detected. Likewise to imaginary movements (IM) and overt movements, QMs are accompanied by the event-related desynchronization (ERD) of EEG sensorimotor rhythms. Stronger ERD was observed under QMs compared to IMs in some studies. However, the difference could be caused by the remaining muscle activation in QMs that could escape detection. Here, we re-examined the relation between the electromyography (EMG) signal and ERD in QM using sensitive data analysis procedures. More trials with signs of muscle activation were observed in QMs compared with a visual task and IMs. However, the rate of such trials was not correlated with subjective estimates of actual movement. Contralateral ERD did not depend on the EMG but still was stronger in QMs compared with IMs. These results suggest that brain mechanisms are common for QMs in the strict sense and "quasi-quasi-movements" (attempts to perform the same task accompanied by detectable EMG elevation) but differ between them and IMs. QMs could be helpful in research aimed at better understanding motor action and at modeling the use of attempted movements in the brain-computer interfaces with healthy participants.

Ambient light at night causes desynchronization of rhythms in the sleep–wake switching model

The purpose of this study is to analyze the influence of the shape of the daily illumination profile on the synchronization of rhythms in the sleep–wake state switching model. Normally, the alternation of sleep and wakefulness of a person is synchronized with his circadian rhythm and with the 24-hour rhythm of illumination. There is, however, a lot of experimental evidence of a violation of this synchronism, both in the form of phase failures (for example, during air travel) and in the form of long-term mismatch of rhythms (for example, during shift work in production). Mathematical models of the process of switching between sleep and wakefulness also demonstrate the desynchronization of rhythms and are successfully used to optimize work schedules. At the same time, the influence of a number of factors on this process has not been sufficiently studied, including the nature of changes in illumination during the day. Methods. An analysis of the six-dimensional model under study shows that, in terms of nonlinear dynamics, the problem is reduced to finding and interpreting resonance regions on a three-dimensional torus. For the specific purposes of our work, it turned out to be convenient to estimate the ratio of three periods (24 hours, the circadian period, and the current duration of the sleep–wake cycle) by numerically integrating the model equations on a grid of parameter values using parallel computing technology. The main result of our work is that the presence of round-the-clock low-intensity illumination (that is, the addition of a zero-frequency signal to the daily light cycle) causes the circadian rhythm to desynchronize with respect to the daily one in a significant range of parameters. We have proposed an explanation of this effect based on the structure of the mathematical model. Conclusion. Our results raise at least two serious questions, the first of which is related to the physiological interpretation of one of the main variables of the model, sleep homeostasis, and the second is to refine the assumptions that are used in the model description of the photoreceptor response. In any case, there are interesting prospects for further research.