Search Results (281)

Background: Chronic work-related stress, including exposure to mobbing, is associated with a wide range of psychological and somatic consequences. However, its potential impact on visual function, particularly in the absence of structural ocular damage, remains underexplored. This narrative review critically examines the evidence linking chronic stress, autonomic nervous system (ANS) dysregulation, and functional visual disorders, focusing on accommodative function and asthenopia. Methods: A qualitative narrative review of the literature published between 2000 and 2025 was conducted using major biomedical databases. Studies addressing chronic stress, ANS activity, accommodative function, digital eye strain, and functional ocular symptoms were identified and integrated into a coherent pathophysiological framework. Results: The ocular system, being richly innervated by the ANS, may represent a peripheral target of prolonged stress-related autonomic alterations. Available evidence suggests that chronic stress is associated with asthenopia, accommodative inefficiency, and ocular discomfort even in the absence of overt ocular pathology. In particular, altered parasympathetic control of the ciliary muscle emerges as a plausible mediating mechanism. Conclusions: Functional visual disorders may represent peripheral manifestations of stress-related ANS dysregulation. Although causality cannot be established conclusively, the proposed framework supports the need for multidisciplinary research to clarify the clinical and medico-legal relevance of stress-related visual dysfunction. Full article

Post-stroke rehabilitation integrates technological feedback systems to enhance motor relearning and autonomic regulation. Among these, physiological biofeedback—based on electromyography (EMG), heart rate variability (HRV) and electrocardiography (ECG)—represents a multimodal approach for restoring neuromotor control and autonomic balance. EMG biofeedback enables patients to visualize and voluntarily modulate muscle activation, supporting cortical reorganization and improving movement precision through real-time feedback. Recent meta-analyses confirm that EMG biofeedback significantly improves upper- and lower-limb function in stroke survivors, particularly when combined with task-oriented physiotherapy. EMG biofeedback demonstrates improvements in swallowing function, motor control, and patient motivation. Beyond the motor domain, HRV biofeedback has shown substantial benefits lately, especially in regulating the autonomic nervous system (ANS) activity, improving vagal tone, and reducing sympathetic overdrive: a major contributor to fatigue and cardiovascular instability post-stroke. By targeting the sympathetic–parasympathetic balance, HRV biofeedback not only enhances autonomic flexibility but also supports emotional and cognitive recovery. Together, these modalities integrate neuromuscular and autonomic rehabilitation, offering a path toward individualized, feedback-driven recovery protocols. This narrative review synthesizes recent evidence on the mechanisms, the clinical outcomes, and translational potential of EMG- and HRV-based biofeedback in stroke rehabilitation, highlighting their role in advancing physiotherapy toward an adaptive, data-driven, and neuroplastic paradigm, as from now on, the emerging directions will include integrating physiological biofeedback with immersive or AI-driven platforms for enhanced personalization and motivation. Full article

Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity and provides insight into physiological and emotional regulation. Evaluating HRV during postural and emotional challenges may help characterize autonomic adaptability in healthy individuals. HRV was recorded in 24 young medical residents (17 females, 7 males; mean age 27.04 ± 1.97 years) during four conditions: rest, orthostatic standing, and exposure to positive and negative emotional images. Each session lasted five minutes. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale. Heart rate increased significantly only during standing, consistent with sympathetic activation with postural change. Spectral and normalized HRV parameters (nLF, nlf, LF/HF, and normalized coherence) were lowest at rest and increased during standing and emotional image exposure, particularly in males. Parasympathetic indices showed opposite trends. Emotional image exposure did not produce significant differences between positive and negative valence at the group level; however, sex- and anxiety-related patterns emerged. Females with anxiety showed increased heart rate during positive image exposure, whereas non-anxious females exhibited higher heart rate responses to negative images. Orthostatic challenge elicited the strongest autonomic response, whereas emotional visual stimuli induced subtler, sex- and anxiety-dependent autonomic modulation without overall changes in heart rate. These preliminary observations suggest that anxiety and sex may be associated with differences in cardiac autonomic regulation in young healthy adults. These results should be interpreted cautiously, given the pilot design, the small sample size (N = 24), the imbalance between sexes, the exclusion of the depression subgroup from inferential analyses, and the use of non-validated emotional visual stimuli Full article

Plasticity is fundamental to the development, strengthening, and maintenance of healthy synaptic connections and recovery from injury in both the central and peripheral nervous systems. Yet, the processes involved are poorly understood. Herein, using a combination of patch-clamp electrophysiology and immuno-fluorescence confocal microscopy in adult mice, it is shown that blockade of synaptic transmission at submandibular ganglion junctions exposed to botulinum neurotoxin type A was accompanied by a rapid and striking decline in the abundance of synaptic vesicle markers—SV2, vesicle-associated membrane protein 2, and vesicular acetylcholine transporter—plus SNAP-25 (cleaved and intact) and postsynaptic α7 nicotinic acetylcholine receptors. Such alterations by the neurotoxin of parasympathetic synapses contrast starkly with the stability of postsynaptic proteins at nearby skeletal neuromuscular junctions. Both neurotransmission and the expression of SV2 and α7 nicotinic acetylcholine receptors remained depressed for 4 weeks, with full recovery of synaptic function delayed for more than 8 weeks. These novel findings may explain the relatively slow recovery of autonomic function after botulism or following therapeutic injections to alleviate hypersecretory disorders. Full article

Background and Objectives: Diabetes mellitus (DM) is a major risk factor for cardiovascular diseases (CVD), including acute myocardial infarction (MI), and is frequently associated with cardiac autonomic neuropathy (CAN). Post-MI autonomic dysfunction contributes to adverse outcomes, but data on prognostic markers in diabetic patients remain limited. This study aimed to (1) compare autonomic nervous system (ANS) function between patients with MI and DM (MI/DM), MI without DM, and DM without MI; (2) assess differences in MI/DM patients based on survival status; and (3) identify prognostic factors for all-cause mortality in diabetic patients following MI. Materials and Methods: This retrospective–prospective study included 375 patients: 93 MI/DM, 229 MI, and 53 DM. MI patients were treated with fibrinolytic or conservative therapy. All participants underwent cardiovascular reflex tests (CARTs) and 24 h Holter ECG with heart rate variability (HRV) analysis; DM patients without MI were tested in an outpatient setting. The primary endpoint was all-cause mortality during a median follow-up of 38 months. Univariable and multivariable Cox regression analyses were performed to determine mortality predictors. Results: Autonomic dysfunction was prevalent in all groups, with MI/DM patients showing the most pronounced impairment, particularly in parasympathetic function. MI/DM patients had significantly lower SDNN values and higher prevalence of definite parasympathetic dysfunction than other groups. In the MI/DM group, abnormal Valsalva maneuver (VM) was more frequent among non-survivors. Multivariable analysis identified abnormal VM and NSTEMI as predictors of overall mortality. Conclusions: Diabetic patients after MI exhibit the most severe autonomic impairment, predominantly parasympathetic, which may contribute to their increased cardiovascular risk. In this high-risk group, abnormal VM and NSTEMI presentations independently predict long-term mortality. Assessment of autonomic function, particularly VM, may provide valuable prognostic information and aid in risk stratification. Full article

This study aims to propose a non-pharmacological approach to pain relief by analyzing changes in electrocardiogram (ECG) parameters following transcutaneous microcurrent stimulation generated according to the pulse train characteristics of intensity and frequency. Therefore, we analyze and interpret stimulation methods that induce parasympathetic nervous system (PNS) activity, which is the clinical basis for pain relief. There were 14 male participants, with a height of 176.08 ± 7.05 cm, a weight of 77.07 ± 10.32 Kg, and an age of 26.35 ± 1.71 years, and 10 female participants, with a height of 160.6 ± 5.88 cm, a weight of 52.9 ± 9.03 Kg, and an age of 24 ± 1.61 years. The microcurrent stimulation patch was attached to the left wrist. In order to observe the PNS induction effect of the measured electrocardiograms, time and frequency domains were analyzed and additional nonlinear analysis was performed. Data measurements had a rest period of more than 1 h depending on the intensity, and more than 1 day depending on the frequency to ensure sufficient stabilization time. Although physiological changes were shown differently in various pulse trains, among them, after 7 Vpp microcurrent stimulation at 1 Hz, the values of the square root of the mean squared differences of successive R-R intervals and instantaneous RR interval variability, which indicate PNS activity in the subjects, significantly increased from 41.31 ± 34.13, 29.23 ± 24.14 ms to 65.09 ± 32.46, 44.56 ± 37.92 ms (p < 0.05). Activation of PNS, which can relieve pain, was confirmed only in the 7 Vpp with 1 Hz stimulation. This suggests that microcurrent stimulation can relieve pain in a non-pharmacological way by inducing activation of PNS. Full article

Prader–Willi syndrome (PWS) is a rare, multisymptomatic genetic disorder caused by the absence or dysfunction of specific genes on chromosome 15. The genetic abnormality is anticipated to cause a dysfunction of the hypothalamus, which is also central in the regulation of the autonomic nervous system (ANS). Typical symptoms of PWS indicating a hypothalamic dysfunction include muscular hypotonia, poor growth, short stature, and feeding difficulties in infancy, which in early childhood are replaced by hyperphagia, leading to a high risk of obesity. Other characteristics, such as sleep difficulties, altered pain perception, delayed gastric emptying and constipation, blood pressure irregularities and dysregulated stress response, altered temperature regulation, delayed pupillary reaction, and urine retention and incontinence, all indicate a dysfunction of ANS. The ANS is usually divided into three parts: the sympathetic nervous system (SNS), which activates the fight-or-flight response during stress; the parasympathetic nervous system (PNS), which promotes calm and digestion; and the independent enteric nervous system (ENS), which regulates the gastrointestinal tract. Noradrenaline is the main neurotransmitter for the SNS, and acetylcholine for the PNS, while the ENS is regulated mainly by acetylcholine and serotonin. However, the ENS is modulated by both the SNS and the PNS, as well as many neuropeptides. Peptides regulating behavior, metabolism, appetite, and satiety have been extensively studied in PWS. However, studies of the role of neuropeptides in regulating other autonomic functions are limited and remain poorly understood. This review aims to synthesize current evidence from both animal models and human studies to explore potential mechanisms by which neuropeptides may contribute to autonomic dysfunction in individuals with PWS. Full article

Background: Coxiella burnetii is a common zoonotic pathogen that can lead not only to acute or chronic Q fever but also to post-infectious syndromes, where autonomic nervous system (ANS) dysfunction has been suggested as a contributing mechanism. This study aimed to assess autonomic function in patients presenting with polymorphic symptoms, dysautonomia, or ME/CFS who had serological evidence of acute infection with Coxiella burnetii. Methods: A total of 156 participants were evaluated, including 100 seropositive patients and 56 matched controls. All subjects underwent standardized cardiovascular reflex tests (CART), beat-to-beat analysis of heart rate and blood pressure with baroreflex indices, 24 h Holter ECG with HRV assessment, and, in the Coxiella group, head-up tilt testing (HUTT). Results: A significantly higher prevalence of autonomic dysfunction was observed in the Coxiella group, predominantly affecting parasympathetic regulation, with abnormal CART scores, reduced LF power and baroreflex effectiveness, and a high rate of positive HUTT findings characterized by extreme blood pressure variability. Although long-term HRV measures did not differ significantly between groups, short-term indices consistently indicated ANS impairment. Conclusions: These findings suggest that Coxiella burnetii infection may trigger persistent autonomic dysfunction, potentially contributing to the development of ME/CFS and syncope in affected individuals. Further longitudinal studies are needed to clarify pathophysiological mechanisms and clinical implications. Full article

Heart rate variability (HRV) is a non-invasive biomarker that reflects autonomic nervous system dynamics, providing valuable insights into physiological adaptation, stress, and recovery in athletes. Among the various HRV metrics, the root mean square of successive differences (RMSSD) has emerged as a robust and practical measure due to its strong association with parasympathetic activity, ease of calculation, and reliability in both short- and ultra-short-term recordings. This review examines the methodological considerations for using HRV to monitor training adaptations and recovery status in athletic populations. We highlight the superiority of routine, near-daily HRV measurements over isolated assessments, emphasizing the utility of weekly averages and the coefficient of variation (CV) to capture both chronic adaptations and acute homeostatic perturbations. Additionally, we discuss the selection of HRV devices, data recording procedures, and strategies to enhance athlete compliance. While RMSSD offers significant advantages for field-based monitoring, we also address its limitations, including its sole focus on parasympathetic activity and susceptibility to external confounders. Future directions include the integration of HRV data with other physiological markers and machine learning algorithms to optimize individualized training and recovery strategies. This review provides sport scientists and practitioners with evidence-based recommendations to enhance the application of HRV in both research and real-world athletic settings. Full article

It has been demonstrated that prolonged exposure to stress engenders a plethora of neuropsychiatric, immune and metabolic disorders. However, its pathophysiology transcends the conventional hypothalamic–pituitary–adrenal (HPA) axis. This review addresses the central question of how integrated neural and microbial pathways regulate stress responses and resilience. We present a model in which the parasympathetic nervous system (particularly the vagus nerve) and the gut microbiota interact to form a bidirectional neuroimmune network that modulates the HPA axis, immune function, neurotransmitter balance, and metabolic adaptation. Key molecular pathways include nitric oxide synthesis via the classical nitric oxide synthase (NOS)-dependent and microbiota-mediated nitrate–nitrite routes, inducible nitric oxide synthase (iNOS) regulation, nuclear factor erythroid 2-related factor 2 (Nrf2) signalling, lysosomal function, autophagy and the cholinergic anti-inflammatory reflex. Other pathways include the gamma-aminobutyric acid (GABA) and serotonin (5-HT) systems, NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signalling, polyamine metabolism and peroxisome proliferator-activated receptor gamma (PPARγ). Intermittent hypoxia training (IHT) enhances mitochondrial function, oxidative stress responses, autonomic balance and gut microbiota composition. This promotes parasympathetic activity and stress resilience that is tailored to the individual. These adaptations support the concept of personalised stress response profiles based on hypoxic adaptability. Clinical implications include combining IHT with vagus nerve stimulation, probiotics, dietary strategies, and stress reduction techniques. Monitoring vagal tone and microbiota composition could also serve as predictive biomarkers for personalised interventions in stress-related disorders. This integrative framework highlights the therapeutic potential of targeting the parasympathetic system and the gut microbiota to modulate stress. Full article

Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity through nonlinear mechanisms, including complex beat-to-beat fluctuations and chaos-like dynamics of healthy cardiac rhythms. However, conventional HRV indices often show inconsistent interpretations of sympathetic activity across studies, making its evaluation difficult. Recently, nonlinear indices such as Acceleration Capacity (AC), Deceleration Capacity (DC), and the non-Gaussianity index have been introduced to separately evaluate sympathetic and parasympathetic nervous activity. We hypothesized that these indices are applicable in dogs and could reflect age-related changes in ANS function. This study provides the first longitudinal evaluation of nonlinear HRV indices, including AC, DC, and the non-Gaussianity index, during puppy growth, highlighting new insights into autonomic maturation in young dogs. HRV was longitudinally measured in eight healthy puppies (4 to 12 months old) of various breeds every two months. HRV analysis was conducted during sleep using 48-h Holter ECG recordings. We applied frequency-domain (nHF, LF/HF), time-domain (SDNN, RMSSD), geometric (SD1, SD2, SD1/SD2), and nonlinear analyses (AC, DC, non-Gaussianity index). Parasympathetic indicators (RMSSD, SD1) and overall HRV indices (SDNN, SD2) significantly increased with age, while the sympathetic indicator AC significantly decreased. No significant changes were observed in nHF, LF/HF, SD1/SD2, DC, or the non-Gaussianity index. HRV analysis suggests that puppies are initially sympathetic-dominant, shifting toward parasympathetic dominance as they grow. AC may serve as a useful marker of sympathetic activity in young dogs, whereas DC and the non-Gaussianity index may provide stable ANS assessments regardless of age. Full article

Background: Only a limited number of studies have investigated objective indicators to assess donkey welfare during Animal-Assisted Services. Objective: The present research follows a single-subject design and its objective is to evaluate the neurovegetative indicators of the well-being of a donkey through spectral analysis of the R-R signal in the frequency domain. Methods: The experimental protocol of the Animal-Assisted Therapy project involved one donkey, previously selected through behavioral protocol evaluation, and ten patients with a diagnosis of paranoid schizophrenia. Spectral analysis of the R-R signal in the frequency domain was performed, providing objective data on the activity of the sympathetic and parasympathetic nervous systems of the donkey (before, during, and after the sessions). Results: The significance of the variations, both statistically significant and not, supports the hypothesis that the affiliative human–donkey interaction within the context of AAS is associated with modifications in the neurovegetative components of the donkey involved in AAT. Conclusions: These findings highlight the importance of objective and non-invasive monitoring tools to detect early signs of discomfort in donkeys involved in AAT, supporting the development of selection and management strategies that safeguard animal welfare. Full article

Against the backdrop of globalization, environmental pressures, and rapid tourism development, digital technologies are emerging as vital supplementary tools for cultural heritage preservation. This study investigates the impact of augmented reality (AR)-enhanced cultural heritage landscapes on rural tourists’ perceptions, validating their effects through two physiological dimensions: visual attention and autonomic nervous system regulation. Employing a mixed experimental design (n = 81), the research integrates heart rate variability, eye tracking, and subjective questionnaires, with the Aoluguya Village in Inner Mongolia serving as the testing site. Participants viewed videos and images of real and AR environments in an isolated space. Data were analyzed using repeated measures ANOVA and paired t-tests. The results revealed that AR significantly increased RMSSD in the native rural environment (t(89) = −3.606, p = 0.001, d = 0.38), indicating heightened parasympathetic activity, while no significant effect was observed in the artificially recreated environment (t(89) = −2.020, p = 0.407), demonstrating that physiological benefits depend on the setting. Eye tracking data revealed that both AR environments increased total gaze duration and gaze frequency (average increase of 1.5–2.0 gazes), enhancing visual attention. The questionnaire results (n = 26) supported this finding on attention focus, novelty, and esthetic dimensions, though improvements in authenticity and overall satisfaction were limited. This study demonstrates that AR environments significantly capture visitor attention, particularly when integrated with authentic local spaces to enhance visitor experiences. The findings provide practical insights for revitalizing traditional village cultural heritage and optimizing rural tourism. Full article

Skin biopsy is an affordable, minimally invasive technique that provides direct access to peripheral neural structures for in vivo evaluation of cutaneous nerve pathology, with relevance to both peripheral and central nervous system disorders. Skin biopsy allows the assessment of somatic and autonomic fibers as well as their innervated structures, representing the gold standard for the diagnosis of Small-Fiber Neuropathy. Nonetheless, the assessment of autonomic fibers remains challenging, as the patterns of sympathetic and parasympathetic skin innervation have not yet been fully elucidated, and the intricate organization of effector structures (e.g., arrector pilorum muscles, sweat glands, blood vessels) poses methodological difficulties. Beyond small-fiber evaluation, skin biopsy allows the detection of disease-specific deposits of abnormally accumulating proteins in a broad spectrum of clinical entities. It has proven highly accurate in detecting synucleinopathies in vivo, with near-complete specificity in the discrimination of affected patients from healthy controls and from alternative neurodegenerative disorders. Furthermore, the pattern of α-synuclein deposition serves to differentiate Lewy body from non-Lewy body synucleinopathies, thereby distinguishing disorders with similar clinical manifestations but distinct physiopathology and prognostic implications. In this narrative review, we outline the current indications for skin biopsy in the evaluation of diverse neurological disorders and address the main methodological aspects of the technique. Full article

Background/Objectives: Postural orthostatic tachycardia syndrome (POTS) is a form of dysautonomia characterized by excessive tachycardia during orthostatic stress. It is frequently observed in patients with syncope, Chronic Fatigue Syndrome (CFS), and post-COVID-19 syndrome (PCS), yet the underlying mechanisms may differ across these conditions. This study aimed to assess autonomic nervous system (ANS) function in patients with syncope, CFS of insidious onset, and CFS post-COVID-19 who presented with POTS, and to compare them with age- and sex-matched patients without POTS. Methods: In this retrospective cross-sectional study, 138 patients over 18 years of age were included following head-up tilt testing (HUTT). Patients were divided into six groups: syncope with and without POTS, CFS with insidious onset with and without POTS, and CFS post-COVID-19 with and without POTS. All participants underwent HUTT, cardiovascular reflex testing (CART) by Ewing, five-minute resting ECG with short-term Heart Rate Variability (HRV) analysis, and 24 h Holter ECG monitoring. Results: The prevalence of POTS across groups ranged from 5% to 7%. Female predominance was consistent across all subgroups. In syncope with POTS, hypertensive responses during HUTT, lower rates of normal Valsalva maneuver results, and reduced HF values in short-term HRV suggested baroreceptor dysfunction with sympathetic overdrive. In both CFS subgroups with POTS, CART revealed higher rates of definite parasympathetic dysfunction, along with more frequent extreme blood pressure variation during HUTT and reduced vagally mediated HRV parameters (rMSSD, pNN50). Across groups, no significant differences were observed with regard to long-term HRV across groups. Conclusions: Distinct autonomic profiles were identified in POTS patients depending on the underlying condition. Syncope-related POTS was associated with baroreceptor dysfunction and sympathetic predominance, whereas CFS-related POTS was characterized by parasympathetic impairment and impaired short-term baroreflex regulation. Evaluating dysautonomia patterns across disease contexts may inform tailored therapeutic strategies and improve management of patients with POTS. Full article