Direct measurement of vagal tone in rats does not show correlation to HRV

ECG-based estimation of respiration-induced autonomic modulation of AV nodal conduction during atrial fibrillation

Introduction: Information about autonomic nervous system (ANS) activity may offer insights about atrial fibrillation (AF) progression and support personalized AF treatment but is not easily accessible from the ECG. In this study, we propose a new approach for ECG-based assessment of respiratory modulation in atrioventricular (AV) nodal refractory period and conduction delay. Methods: A 1-dimensional convolutional neural network (1D-CNN) was trained to estimate respiratory modulation of AV nodal conduction properties from 1-minute segments of RR series, respiration signals, and atrial fibrillatory rates (AFR) using synthetic data that replicates clinical ECG-derived data. The synthetic data were generated using a network model of the AV node and 4 million unique model parameter sets. The 1D-CNN was then used to analyze respiratory modulation in clinical deep breathing test data of 28 patients in AF, where an ECG-derived respiration signal was extracted using a novel approach based on periodic component analysis. Results: We demonstrated using synthetic data that the 1D-CNN can estimate the respiratory modulation from RR series alone with a Pearson sample correlation of r = 0.805 and that the addition of either respiration signal (r = 0.830), AFR (r = 0.837), or both (r = 0.855) improves the estimation. Discussion: Initial results from analysis of ECG data suggest that our proposed estimate of respiration-induced autonomic modulation, a resp, is reproducible and sufficiently sensitive to monitor changes and detect individual differences. However, further studies are needed to verify the reproducibility, sensitivity, and clinical significance of a resp.

Personal versus therapist perioperative music intervention: a randomized controlled trial

INTRODUCTION

Music interventions can alleviate patient anxiety and improve post-surgical satisfaction. However, it remains uncertain whether music personal preferences affect efficacy. We tested whether personal music intervention with patient-selected songs played ad libitum is more effective than standard therapist-designed treatment with classical music.

METHODS

A prospective, parallel-group, single-blinded, randomized controlled trial with 229 participants (aged 18 to 60 y) previously scheduled for elective surgery. Data analyses followed a modified intention-to-treat principle. The patients were randomized into three groups: Standard care without music (Control), therapist-designed classic music treatment (TT), or personal music intervention with patient-selected songs played ad libitum by the patient (PI). All patients received standard post-anesthesia care, and music intervention was started upon arrival at the post-anesthesia care unit. Primary outcomes were anxiety and overall satisfaction at discharge. In contrast, secondary outcomes were systolic blood pressure during music intervention, the sleep quality of the night after surgery, and the occurrence of postoperative nausea and vomiting within the first 24 hours after surgery.

RESULTS

Compared with therapist-designed music treatment, personal intervention decreased systolic blood pressure (T 0 : 124.3±13.7, 95%CI:121-127.7; T 20min : 117.6±10.4, 95%CI:115-120.1; T 30min : 116.9±10.6, 95%CI:114.3-119.4), prevented postoperative nausea and vomiting (Control: 55.9%, TT: 64.6%, PI: 77.6%), including severe postoperative nausea (VAS score>4; Control:44.1%; TT:33.8%; PI:20.9%) and severe emesis (Frequency≥3, Control:13.2%; TT:7.7%; PI:4.5%). None of the treatments affected sleep quality at night after surgery (Median, Q1-Q3, Control:3,1-3; TT:3,1-4; PI:3,1-3.5). Personal, but not therapist, music intervention significantly prevented anxiety (Control: 36.4±5.9, 95% CI:35.0-37.9; TT: 36.2±7.1, 95%CI: 34.4-37.9; PI: 33.8±5.6, 95%CI: 32.4-35.2) and emesis (Control:23.9%; TT:23.4%; PI:13.2%) and improved patient satisfaction (Median, Q1-Q3, C:8, 6-8; TT:8,7-9; PI:8,7-9).

CONCLUSIONS

Personal music intervention improved postoperative systolic blood pressure, anxiety, nausea, emesis, and overall satisfaction, but not sleep quality, as compared to therapist-designed classic intervention.

Dorsal motor vagal neurons can elicit bradycardia and reduce anxiety-like behavior

Cardiovagal neurons (CVNs) innervate cardiac ganglia through the vagus nerve to control cardiac function. Although the cardioinhibitory role of CVNs in nucleus ambiguus (CVNNA) is well established, the nature and functionality of CVNs in dorsal motor nucleus of the vagus (CVNDMV) is less clear. We therefore aimed to characterize CVNDMV anatomically, physiologically, and functionally. Optogenetically activating cholinergic DMV neurons resulted in robust bradycardia through peripheral muscarinic (parasympathetic) and nicotinic (ganglionic) acetylcholine receptors, but not beta-1-adrenergic (sympathetic) receptors. Retrograde tracing from the cardiac fat pad labeled CVNNA and CVNDMV through the vagus nerve. Using whole-cell patch-clamp, CVNDMV demonstrated greater hyperexcitability and spontaneous action potential firing ex vivo despite similar resting membrane potentials, compared to CVNNA. Chemogenetically activating DMV also caused significant bradycardia with a correlated reduction in anxiety-like behavior. Thus, DMV contains uniquely hyperexcitable CVNs and is capable of cardioinhibition and robust anxiolysis.

Motor Dysfunctions in Fibromyalgia Patients: The Importance of Breathing

The classification of fibromyalgia (FM) is not always immediate and simple, with the time from the first diagnosis, compared to the onset of symptoms, of a few years. Currently, we do not have instrumental or biochemical tests considered as gold standards; the clinician will make a diagnosis of FM based on the patient's medical history and subjective assessment. The symptoms can involve physical, cognitive and psychological disorders, with the presence of pain of different origins and classifications: nociplastic, nociceptive and neuropathic pain. Among the symptoms highlighted, postural disorders and neuromotor uncoordination emerge, whose functional dysfunctions can increase the mortality and morbidity rate. An alteration of the diaphragm muscle could generate such functional motor problems. Considering that the current literature underestimates the importance of breathing in FM, the article aims to highlight the relationship between motor and diaphragmatic difficulties in the patient, soliciting new points of view for the clinical and therapeutic framework.

The moderating effect of resting heart rate variability on the relationship between pain catastrophizing and depressed mood: an empirical study

Previous research indicated that pain catastrophizing-a negative emotional and cognitive response toward actual or anticipated pain-could contribute to pain intensity and could be associated with depressive symptoms not just in chronic pain patients but in healthy population as well. Accumulated evidence suggests that resting heart rate variability (HRV) as a putative proxy of emotion regulation could moderate the association of self-reported pain catastrophizing and depressed mood. In the present cross-sectional study, we investigated these associations in a healthy young adult sample controlling for the effect of trait rumination. Seventy-two participants (58 females, mean age = 22.2 ± 1.79 years ranging from 19 to 28 years old) completed the Pain Catastrophizing Scale, the Zung Self-Rating Depression Scale and the Ruminative Response Scale. Resting HRV was measured by time domain metric of HRV, the root mean square of successive differences (RMSSD). The results showed that the relationship between pain catastrophizing and depressive symptoms is significantly moderated by resting HRV (indexed by lnRMSSD). Specifically, in participants with higher resting HRV there was no significant relationship between the two investigated variables, while in participants with relatively low or medium HRV pain catastrophizing and depressed mood showed significant positive association. The relationship remained significant after controlling for sex, age and trait rumination. These results might indicate that measuring pain catastrophizing and depressive symptoms is warranted in non-clinical samples as well and higher resting HRV could have a buffer or protective role against depressive symptoms.

Selective chronic recording in small nerve fascicles of sciatic nerve with carbon nanotube yarns in rats

Objective. The primary challenge faced in the field of neural rehabilitation engineering is the limited advancement in nerve interface technology, which currently fails to match the mechanical properties of small-diameter nerve fascicles. Novel developments are necessary to enable long-term, chronic recording from a multitude of small fascicles, allowing for the recovery of motor intent and sensory signals.Approach. In this study, we analyze the chronic recording capabilities of carbon nanotube yarn electrodes in the peripheral somatic nervous system. The electrodes were surgically implanted in the sciatic nerve's three individual fascicles in rats, enabling the recording of neural activity during gait. Signal-to-noise ratio (SNR) and information theory were employed to analyze the data, demonstrating the superior recording capabilities of the electrodes. Flat interface nerve electrode and thin-film longitudinal intrafascicular electrode electrodes were used as a references to assess the results from SNR and information theory analysis.Main results. The electrodes exhibited the ability to record chronic signals with SNRs reaching as high as 15 dB, providing 12 bits of information for the sciatic nerve, a significant improvement over previous methods. Furthermore, the study revealed that the SNR and information content of the neural signals remained consistent over a period of 12 weeks across three different fascicles, indicating the stability of the interface. The signals recorded from these electrodes were also analyzed for selectivity using information theory metrics, which showed an information sharing of approximately 1.4 bits across the fascicles.Significance. The ability to safely and reliably record from multiple fascicles of different nerves simultaneously over extended periods of time holds substantial implications for the field of neural and rehabilitation engineering. This advancement addresses the limitation of current nerve interface technologies and opens up new possibilities for enhancing neural rehabilitation and control.

Left cardiac vagotomy rapidly reduces contralateral cardiac vagal electrical activity in anesthetized Göttingen minipigs

BACKGROUND

The impact of acute unilateral injury on spontaneous electrical activity in both vagus nerves at the heart level is poorly understood. We investigated the immediate neuroelectrical response after right or left cardiac vagal nerve transection (VNTx) by recording spiking activity of each heart vagus nerve (VN).

METHODS

Fourteen male Göttingen minipigs underwent sternotomy. Multi-electrode cuffs were implanted below the cut level to record vagal electroneurographic signals during electrocardiographic and hemodynamic monitoring, before and immediately after cardiac VNTx (left: L-cut, n = 6; right: R-cut, n = 8).

RESULTS

Left cardiac VNTx significantly reduced multi-unit electrical activity (MUA) firing rate in the vagal stump (-30.7% vs pre-cut) and intact right VN (-21.8% vs pre-cut) at the heart level, without affecting heart rate, heart rate variability, or hemodynamics. In contrast, right cardiac VNTx did not acutely alter MUA in either VN but slightly increased (p < 0.022) the root mean square of successive RR interval differences (rMSSD), an index of parasympathetic outflow, without affecting hemodynamics.

CONCLUSIONS

Our study reveals an early left-lateralized pattern in vagal spiking activity following unilateral cardiac vagotomy. These findings enhance understanding of the neuroelectrical response to vagal injury and provide insights into preserving vagal outflow after unilateral cardiac vagotomy. Importantly, monitoring spiking activity of the cardiac right VN may predict onset of left vagal pathway injury, which is detrimental to cardiac patients and can occur as a complication of catheter ablation for atrial fibrillation.

Dorsal Motor Vagal Neurons Can Elicit Bradycardia and Reduce Anxiety-Like Behavior

Cardiovagal neurons (CVNs) innervate cardiac ganglia through the vagus nerve to control cardiac function. Although the cardioinhibitory role of CVNs in nucleus ambiguus (CVNNA) is well established, the nature and functionality of CVNs in dorsal motor nucleus of the vagus (CVNDMV) is less clear. We therefore aimed to characterize CVNDMV anatomically, physiologically, and functionally. Optogenetically activating cholinergic DMV neurons resulted in robust bradycardia through peripheral muscarinic (parasympathetic) and nicotinic (ganglionic) acetylcholine receptors, but not beta-1-adrenergic (sympathetic) receptors. Retrograde tracing from the cardiac fat pad labeled CVNNA and CVNDMV through the vagus nerve. Using whole cell patch clamp, CVNDMV demonstrated greater hyperexcitability and spontaneous action potential firing ex vivo despite similar resting membrane potentials, compared to CVNNA. Chemogenetically activating DMV also caused significant bradycardia with a correlated reduction in anxiety-like behavior. Thus, DMV contains uniquely hyperexcitable CVNs capable of cardioinhibition and robust anxiolysis.

Immediate and sustained increases in the activity of vagal preganglionic neurons during exercise and after exercise training

AIMS

The brain controls the heart by dynamic recruitment and withdrawal of cardiac parasympathetic (vagal) and sympathetic activity. Autonomic control is essential for the development of cardiovascular responses during exercise, however, the patterns of changes in the activity of the two autonomic limbs, and their functional interactions in orchestrating physiological responses during exercise, are not fully understood. The aim of this study was to characterize changes in vagal parasympathetic drive in response to exercise and exercise training by directly recording the electrical activity of vagal preganglionic neurons in experimental animals (rats).

METHODS AND RESULTS

Single unit recordings were made using carbon-fibre microelectrodes from the populations of vagal preganglionic neurons of the nucleus ambiguus (NA) and the dorsal vagal motor nucleus of the brainstem. It was found that (i) vagal preganglionic neurons of the NA and the dorsal vagal motor nucleus are strongly activated during bouts of acute exercise, and (ii) exercise training markedly increases the resting activity of both populations of vagal preganglionic neurons and augments the excitatory responses of NA neurons during exercise.

CONCLUSIONS

These data show that central vagal drive increases during exercise and provide the first direct neurophysiological evidence that exercise training increases vagal tone. The data argue against the notion of exercise-induced central vagal withdrawal during exercise. We propose that robust increases in the activity of vagal preganglionic neurons during bouts of exercise underlie activity-dependent plasticity, leading to higher resting vagal tone that confers multiple health benefits associated with regular exercise.

A multivariate physiological model of vagus nerve signalling during metabolic challenges in anaesthetised rats for diabetes treatment

Objective.This study aims to develop a comprehensive decoding framework to create a multivariate physiological model of vagus nerve transmission that reveals the complex interactions between the nervous and metabolic systems.Approach.Vagus nerve activity was recorded in female Sprague-Dawley rats using gold hook microwires implanted around the left cervical vagus nerve. The rats were divided into three experimental cohorts (intact nerve, ligation nerve for recording afferent activation, and ligation for recording efferent activation) and metabolic challenges were administered to change glucose levels while recording the nerve activity. The decoding methodology involved various techniques, including continuous wavelet transformation, extraction of breathing rate (BR), and correlation of neural metrics with physiological signals.Main results.Decrease in glucose level was consistently negatively correlated with an increase in the firing activity of the intact vagus nerve that was found to be conveyed by both afferent and efferent pathways, with the afferent response being more similar to the one on the intact nerve. A larger variability was observed in the sensory and motor responses to hyperglycaemia. A novel strategy to extract the BR over time based on inter-burst-interval is also presented. The vagus afferent was found to encode breathing information through amplitude and firing rate modulation. Modulations of the signal amplitude were also observed due to changes in heart rate in the intact and efferent recordings, highlighting the parasympathetic control of the heart.Significance.The analytical framework presented in this study provides an integrative understanding that considers the relationship between metabolic, cardiac, and breathing signals and contributes to the development of a multivariable physiological model for the transmission of vagus nerve signals. This work progresses toward the development of closed-loop neuro-metabolic therapeutic systems for diabetes.

Putative role of non-invasive vagus nerve stimulation in cancer pathology and immunotherapy: Can this be a hidden treasure, especially for the elderly?

Cancer is globally a disease of significant public health concern owing to its prevalence, and association with morbidity and mortality. Thus, cost-effective treatments for cancer are important to help reduce its significant morbidity and mortality. However, the current therapeutic options for cancer such as chemotherapy, radiotherapy, and surgery may produce serious adverse events such as nausea, vomiting, fatigue, and peripheral neuropathy, especially in the long term. In addition, these therapeutic options may not be well tolerated by the elderly especially those who are frail. The current article is aimed at discussing an alternative therapeutic option, non-invasive vagus nerve stimulation (VNS), and the roles it plays in cancer pathology and immunotherapy. The VNS does this by reducing oxidative stress via silent information regulator 1 (SIRT1); inhibiting inflammation via both hypothalamic-pituitary-axis (HPA) and the release of corticosteroid from the adrenal gland, and cholinergic anti-inflammatory pathway (CAP), and increasing vagal activity which helps in the regulation of cell proliferation, differentiation, apoptosis, and metabolism, and increase chance of survival. Furthermore, it helps with reducing complications due to cancer or its treatments such as postoperative ileus and severity of peripheral neuropathy induced by chemotherapy, and improves cancer-related fatigue, lymphopenia, and quality of life. These suggest that the importance of non-invasive VNS in cancer pathology and immunotherapy cannot be overemphasized. Therefore, considering the safety of non-invasive VNS and its cost-effectiveness, it is a therapeutic option worth trying for these patients, especially in combination with other therapies.

Selection of patients with symptomatic vagal-induced sinus node dysfunction: Who will be the best candidate for cardioneuroablation?

Sinus node dysfunction is a multifaceted disorder with variable manifestations, the prevalence of which increases with age. In a specific group of patients, excessive vagal activity may be the sole cause for this condition. These patients are characterized as having recurrent daytime symptoms attributed to bradyarrhythmia, no evidence of organic sinus node lesions, cardiac vagal overactivation, and are non-elderly. For sinus node dysfunction patients, a permanent pacemaker implantation appears to be the ultimate solution, although it is not an etiological treatment. Cardioneuroablation is a promising emerging therapy that can fundamentally eliminate symptoms in a highly selective sub-set of sinus node dysfunction patients by cardiac vagal nerve denervation. Denervation with ablation for vagal-induced sinus node dysfunction can effectively improve sinus bradycardia and reduce syncope. To date, guidelines for selection of suitable candidates for cardioneuroablation remain lacking. The primary objective of this study was to distinguish the nature of abnormal sinus node function and to find methods for quantifying vagal tone. Clear selection criteria could help physicians in identification of patients with autonomic imbalance, thereby maximizing patient benefits and the success rate of cardioneuroablations.

Heart Rate Asymmetry, Its Compensation, and Heart Rate Variability in Healthy Adults during 48-h Holter ECG Recordings

Heart rate asymmetry (HRA) reflects different contributions of heart rate (HR) decelerations and accelerations to heart rate variability (HRV). In this study, we examined various properties of HRA, including its compensation and HRV, in 48-h electrocardiogram (ECG) recordings in healthy adults. Furthermore, we compared sex differences in parameters used to quantify HRA and HRV. Variance-based and relative HRA and HRV parameters were computed for Holter ECG recordings lasting up to 48 h in 101 healthy volunteers. The median age of the subjects was 39 years, with 47 of them being men. The prevalence of all forms of HRA was statistically different from randomness (p < 0.0001). Specifically, HR decelerations contributed >50% (C1d) to short-term HRA in 98.02% of subjects, while HR decelerations contributed <50% to long-term HRA in 89.11% of recordings and to total HRA in 88.12% of recordings. Additionally, decelerations accounted for <50% of all changing heartbeats (Porta's index) in 74.26% of subjects, and HRA compensation was present in 88.12% of volunteers. Our findings suggest that various HRA features are present in most healthy adults. While men had more pronounced HRA expression, the prevalence of short-, long-term, and total HRA and its compensation was similar in both sexes. For HRV, values of variance-based indices were higher in men than in women, but no differences were found for relative measures. In conclusion, our study references HRA and HRV for longer ECG recordings of up to 48 h, which have become increasingly important in clinical ECG monitoring. The findings can help understand and compare the characteristics of HRA and HRV in patients with different diseases.

Heart Rate Asymmetry in Healthy Children

Heart rate asymmetry (HRA) is a physiological phenomenon characterized by an unequal contribution of heart rate decelerations and accelerations to different heart rate variability (HRV) features. While HRA has been demonstrated in adults' ECGs of different duration, a similar investigation in healthy children has not been conducted. This study investigated the variance- and number-based HRA features in 96 healthy children (50 girls and 46 boys, aged 3-18 years) using 24-h ECGs. Additionally, we studied sex differences in HRA. To quantify HRA, variance-based and relative contributions of heart rate decelerations to short-term (C1d), long-term (C2d), and total (CTd) HRV, and the number of all heartbeats (Nd) were computed. Heart rate decelerations contributed more to C1d, but less to C2d and CTd, and were less frequent than heart rate accelerations. Short-term HRA was better expressed in boys. The majority of children (93.7%) had short-term HRA, 88.5% had long-term HRA, 88.5% had total HRA, and 99.0% had more accelerations than decelerations. No sex differences were observed for the rate of various HRA features. Heart rate asymmetry is a common phenomenon in healthy children, as observed in 24-h ECGs. Our findings can be used as reference data for future clinical studies on HRA in children.

Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials

Deliberate control of the breath (breathwork) has recently received an unprecedented surge in public interest and breathing techniques have therapeutic potential to improve mental health. Our meta-analysis primarily aimed to evaluate the efficacy of breathwork through examining whether, and to what extent, breathwork interventions were associated with lower levels of self-reported/subjective stress compared to non-breathwork controls. We searched PsycInfo, PubMed, ProQuest, Scopus, Web of Science, ClinicalTrials.gov and ISRCTN up to February 2022, initially identifying 1325 results. The primary outcome self-reported/subjective stress included 12 randomised-controlled trials (k = 12) with a total of 785 adult participants. Most studies were deemed as being at moderate risk of bias. The random-effects analysis yielded a significant small-to-medium mean effect size, g = - 0.35 [95% CI - 0.55, - 0.14], z = 3.32, p = 0.0009, showing breathwork was associated with lower levels of stress than control conditions. Heterogeneity was intermediate and approaching significance, χ²₁₁ = 19, p = 0.06, I² = 42%. Meta-analyses for secondary outcomes of self-reported/subjective anxiety (k = 20) and depressive symptoms (k = 18) showed similar significant effect sizes: g = - 0.32, p < 0.0001, and g = - 0.40, p < 0.0001, respectively. Heterogeneity was moderate and significant for both. Overall, results showed that breathwork may be effective for improving stress and mental health. However, we urge caution and advocate for nuanced research approaches with low risk-of-bias study designs to avoid a miscalibration between hype and evidence.

The Importance of the Diaphragm in Neuromotor Function in the Patient with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a constant and chronic narrowing of the respiratory airways, with numerous associated symptoms, not always related to the pathological adaptation of the lungs. Statistical projections show that COPD could become the third leading cause of death globally by 2030, with a significant increase in deaths by 2060. Skeletal muscle dysfunction, including the diaphragm, is one of the causes linked to the increase in mortality and hospitalization. Little emphasis is given by the scientific literature to the importance of the diaphragm towards functional neuromotor pathological expressions. The article reviews the adaptation of the skeletal muscles, with greater attention to the adaptations of the diaphragm, thereby highlighting the non-physiological variations that the main respiratory muscle undergoes and the neuromotor impairment found in COPD. The text could be an important reflection from a clinical and rehabilitation point of view, to direct greater attention to the function and adaptation of the diaphragm muscle.

The role of age-associated autonomic dysfunction in inflammation and endothelial dysfunction

Aging of the cardiovascular regulatory function manifests as an imbalance between the sympathetic and parasympathetic (vagal) components of the autonomic nervous system (ANS). The most characteristic change is sympathetic overdrive, which is manifested by an increase in the muscle sympathetic nerve activity (MSNA) burst frequency with age. Age-related changes that occur in vagal nerve activity is less clear. The resting tonic parasympathetic activity can be estimated noninvasively by measuring the increase in heart rate occurring in response to muscarinic cholinergic receptor blockade; animal study models have shown this to diminish with age. Humoral, cellular, and neural mechanisms work together to prevent non-resolving inflammation. This review focuses on the mechanisms underlying age-related alternations in the ANS and how an imbalance in the ANS, evaluated by MSNA and heart rate variability (HRV), potentially facilitates inflammation when the homeostatic mechanisms between reflex neural circuits and the immune system are compromised, particularly the dysfunction of the cholinergic anti-inflammatory reflex. Physiologically, the efferent arm of this reflex acts via the [Formula: see text] 7 nicotinic acetylcholine receptors expressed in macrophages, monocytes, dendritic cells, T cells, and endothelial cells to curb the release of inflammatory cytokines, in which inhibition of NF‑κB nuclear translocation and activation of a JAK/STAT-mediated signaling cascade in macrophages and other immune cells are implicated. This reflex is likely to become less adequate with advanced age. Consequently, a pro-inflammatory state induced by reduced vagus output with age is associated with endothelial dysfunction and may significantly contribute to the development and propagation of atherosclerosis, heart failure, and hypertension. The aim of this review is to summarize the relationship between ANS dysfunction, inflammation, and endothelial dysfunction in the context of aging. Meanwhile, this review also attempts to describe the role of HRV measures as a predictor of the level of inflammation and endothelial dysfunction in the aged population and explore the possible therapeutical effects of vagus nerve stimulation.

Meditative-based diaphragmatic breathing vs. vagus nerve stimulation in the treatment of fibromyalgia-A randomized controlled trial: Body vs. machine

IMPORTANCE

Vagus nerve innervation via electrical stimulation and meditative-based diaphragmatic breathing may be promising treatment avenues for fibromyalgia.

OBJECTIVE

Explore and compare the treatment effectiveness of active and sham transcutaneous vagus nerve stimulation (tVNS) and meditative-based diaphragmatic breathing (MDB) for fibromyalgia.

DESIGN

Participants enrolled from March 2019-October 2020 and randomly assigned to active tVNS (n = 28), sham tVNS (n = 29), active MDB (n = 29), or sham MDB (n = 30). Treatments were self-delivered at home for 15 min/morning and 15 min/evening for 14 days. Follow-up was at 2 weeks.

SETTING

Outpatient pain clinic in Oslo, Norway.

PARTICIPANTS

116 adults aged 18-65 years with severe fibromyalgia were consecutively enrolled and randomized. 86 participants (74%) had an 80% treatment adherence and 107 (92%) completed the study at 2 weeks; 1 participant dropped out due to adverse effects from active tVNS.

INTERVENTIONS

Active tVNS is placed on the cymba conchae of the left ear; sham tVNS is placed on the left earlobe. Active MDB trains users in nondirective meditation with deep breathing; sham MDB trains users in open-awareness meditation with paced breathing.

MAIN OUTCOMES AND MEASURES

Primary outcome was change from baseline in ultra short-term photoplethysmography-measured cardiac-vagal heart rate variability at 2 weeks. Prior to trial launch, we hypothesized that (1) those randomized to active MDB or active tVNS would display greater increases in heart rate variability compared to those randomized to sham MDB or sham tVNS after 2-weeks; (2) a change in heart rate variability would be correlated with a change in self-reported average pain intensity; and (3) active treatments would outperform sham treatments on all pain-related secondary outcome measures.

RESULTS

No significant across-group changes in heart rate variability were found. Furthermore, no significant correlations were found between changes in heart rate variability and average pain intensity during treatment. Significant across group differences were found for overall FM severity yet were not found for average pain intensity.

CONCLUSIONS AND RELEVANCE

These findings suggest that changes in cardiac-vagal heart rate variability when recorded with ultra short-term photoplethysmography in those with fibromyalgia may not be associated with treatment-specific changes in pain intensity. Further research should be conducted to evaluate potential changes in long-term cardiac-vagal heart rate variability in response to noninvasive vagus nerve innervation in those with fibromyalgia.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT03180554, Identifier: NCT03180554.

Cardiovascular Function in Different Phases of the Menstrual Cycle in Healthy Women of Reproductive Age

Background: Sex hormones influence the cardiovascular (CV) function in women. However, it is uncertain whether their physiological variation related to the regular menstrual cycle affects the CV system. We studied changes in the hemodynamic profile and body’s water content and their relation to sex hormone concentration in healthy women during the menstrual cycle. Material and methods: Forty-five adult women were examined during the early follicular, late follicular, and mid-luteal phases of the same menstrual cycle. The hemodynamic profile was estimated non-invasively by cardiac impedance while water content was estimated by total body impedance. Results were compared with repeated measures ANOVA with post-test, if applicable. Results: There were no significant changes in most hemodynamic and water content parameters between the menstrual cycle phases in healthy women. Left ventricular ejection time differed significantly among phases of the menstrual cycle, with shorter values in the mid-luteal phase (308.4 vs. 313.52 ms, p < 0.05) compared to the late follicular phase. However, the clinical relevance of such small differences is negligible. Conclusions: Changes in sex hormones during the physiological menstrual cycle appear to have no considerable effect on healthy women’s hemodynamic function and water accumulation.

Functional anatomy of the vagus system: How does the polyvagal theory comply?

Due to its pivotal role in autonomic networks and interoception, the vagus attracts continued interest from both basic scientists and therapists of various clinical disciplines. In particular, the widespread use of heart rate variability as an index of autonomic cardiac control and a proposed central role of the vagus in biopsychological concepts, e.g., the polyvagal theory, provide a good opportunity to recall basic features of vagal anatomy. In addition to the "classical" vagal brainstem nuclei, i.e., dorsal motor nucleus, nucleus ambiguus and nucleus tractus solitarii, the spinal trigeminal and paratrigeminal nuclei come into play as targets of vagal afferents. On the other hand, the nucleus of the solitary tract receives and integrates not only visceral but also somatic afferents.

Dynamic coupling between the central and autonomic cardiac nervous systems in patients with refractory epilepsy: A pilot study

The heart and brain are reciprocally interconnected and engage in two-way communication for homeostatic regulation. Epilepsy is considered a network disease that also affects the autonomic nervous system (ANS). The neurovisceral integration model (NVM) proposes that cardiac vagal tone, indexed by heart rate variability (HRV), can indicate the functional integrity of cognitive neural networks. ANS activity and the pattern of oscillatory EEG activity covary during the transition of arousal states and associations between cortical and autonomic activity are reflected by HRV. Cognitive dysfunction is one of the common comorbidities that occur in epilepsy, including memory, attention, and processing difficulties. Recent studies have shown evidence for the active involvement of alpha activity in cognitive processes through its active role in the control of neural excitability in the cortex through top-down modulation of cortical networks. In the present pilot study, we evaluated the association between resting EEG oscillatory behavior and ANS function in patients with refractory epilepsy. Our results show: (1) In patients with refractory epilepsy, there is a strong positive correlation between HRV and the power of cortical oscillatory cortical activity in all studied EEG bands (delta, theta, alpha, and beta) in all regions of interest in both hemispheres, the opposite pattern found in controls which had low or negative correlation between these variables; (2) higher heartbeat evoked potential amplitudes in patients with refractory epilepsy than in controls. Taken together, these results point to a significant alteration in heart-brain interaction in patients with refractory epilepsy.

The Neuroimmune Response to Surgery – An Exploratory Study of Trauma-Induced Changes in Innate Immunity and Heart Rate Variability

Surgery triggers a systemic inflammatory response that ultimately impacts the brain and associates with long-term cognitive impairment. Adequate regulation of this immune surge is pivotal for a successful surgical recovery. We explored the temporal immune response in a surgical cohort and its associations with neuroimmune regulatory pathways and cognition, in keeping with the growing body of evidence pointing towards the brain as a regulator of peripheral inflammation. Brain-to-immune communication acts through cellular, humoral and neural pathways. In this context, the vagal nerve and the cholinergic anti-inflammatory pathway (CAP) have been shown to modify peripheral immune cell activity in both acute and chronic inflammatory conditions. However, the relevance of neuroimmune regulatory mechanisms following a surgical trauma is not yet elucidated. Twenty-five male patients undergoing elective laparoscopic abdominal surgery were included in this observational prospective study. Serial blood samples with extensive immune characterization, assessments of heart rate variability (HRV) and cognitive tests were performed before surgery and continuing up to 6 months post-surgery. Temporal immune responses revealed biphasic reaction patterns with most pronounced changes at 5 hours after skin incision and 14 days following surgery. Estimations of cardiac vagal nerve activity through HRV recordings revealed great individual variations depending on the pre-operative HRV baseline. A principal component analysis displayed distinct differences in systemic inflammatory biomarker trajectories primarily based on pre-operative HRV, with potiential consequences for long-term surgical outcomes. In conclusion, individual pre-operative HRV generates differential response patterns that associate with distinct inflammatory trajectories following surgery. Long-term surgical outcomes need to be examined further in larger studies with mixed gender cohorts.

Do common antibiotic treatments influence emotional processing?

Antibiotics are among the most commonly prescribed medications worldwide, yet research in recent years has revealed the detrimental effect they can have on the human microbiome, with implications for health. The community of microorganisms inhabiting the gut has been shown to regulate physiological and neural processes. Since studies in both humans and animal models have revealed that the gut microbiome can affect the brain, influencing emotion and cognition, here we investigate whether antibiotic treatment is associated with changes in emotional processing and mood with a between-subject design in 105 young healthy adult volunteers, using both psychological tests and questionnaires. As both the immune system and vagal signalling can mediate the microbiome-gut-brain axis, we also assess whether there is any evidence of such changes in participant physiology. We find that individuals who have taken antibiotics in the past three months show a stronger emotional bias towards sadness and at a physiological level they have a higher heart rate (though this does not mediate the relationship with negative bias). While we cannot rule out a possible role of prior infection, our findings are in any case highly relevant in light of research revealing that antibiotics are linked to increased susceptibility to depression and anxiety. Our results also have implications for listing antibiotic use as an exclusion criterion in studies on emotional processing and psychophysiology.

Chronic recording of the vagus nerve to analyze modulations by the light-dark cycle

OBJECTIVE

The vagus nerve is considered to play a key role in the circadian rhythm. Chronic continuous analysis of the vagus nerve activity could contribute to a better understanding of the role of the vagus nerve in light-dark modulations. This paper presents a continuous analysis of spontaneous vagus nerve activity performed in four rats.

APPROACH

We analyzed the vagus electroneurogram (VENG) and electroencephalogram (EEG) over a recording period of 28 days. Spike activity and heart rate estimation were derived from the VENG, and slow-wave activity was derived from the EEG. The presence of repetitive patterns was investigated with periodograms, cosinor fitting, autocorrelation, and statistical tests. The light-dark variations derived from the VENG spikes were compared with EEG slow waves, an established metric in circadian studies.

RESULTS

Our results demonstrate that light-dark variations can be detected in long-term vagus nerve activity monitoring. A recording period of about seven days is required to characterize accurately the VENG light-dark variations.

SIGNIFICANCE

As a major outcome of this study, vagus nerve recordings hold the promise to help understand circadian regulation.

Reliability of Heart Rate Variability During Stable and Disrupted Polysomnographic Sleep

Heart rate variability (HRV) is commonly used within sleep and cardiovascular research, yet HRV reliability across various sleep stages remains equivocal. The present study examined the reliability of frequency- and time-domain HRV within stage II (N2), slow wave (SWS), and rapid eye movement (REM) sleep during both stable and disrupted sleep. We hypothesized that high-frequency (HF) HRV would be reliable in all three sleep stages, low-frequency (LF) HRV would be reliable during N2 and SWS, and that disrupted sleep via spontaneous cortical arousals would decrease HRV reliability. Twenty-seven participants (11 male, 16 female, 26±1 years) were equipped with laboratory polysomnography for one night. Both frequency- and time-domain HRV were analyzed in two 5-10 minute blocks during multiple stable and disrupted sleep cycles across N2, SWS and REM sleep. HF HRV was highly correlated across stable N2 (r=0.839, p<0.001), SWS (r=0.765, p<0.001) and REM (r=0.881, p<0.001). LF HRV was moderate-to-highly correlated during stable cycles of N2 sleep (r=0.694, p < 0.001), SWS, (r=0.765, p < 0.001), and REM (r=0.699, p<0.001) sleep. When stable sleep was compared with disrupted sleep, both time- and frequency-domain HRV were reliable (α>0.90, p<0.05) in N2, SWS, and REM, with the exception of LF HRV during SWS (α=0.62, p=0.089). In conclusion, time- and frequency-domain HRV demonstrated reliability across stable N2, SWS and REM sleep, and remained reliable during disrupted sleep. These findings support the use of HRV during sleep as a tool for assessing cardiovascular health and risk stratification.

Single-interface bioelectronic medicines - concept, clinical applications and preclinical data

Presently, large groups of patients with various diseases are either intolerant, or irresponsive to drug therapies and also intractable by surgery. For several diseases, one option which is available for such patients is the implantable neurostimulation therapy. However, lacking closed-loop control and selective stimulation capabilities, the present neurostimulation therapies are not optimal and are therefore used as only "third" therapeutic options when a disease cannot be treated by drugs or surgery. Addressing those limitations, a next generation class of closed-loop controlled and selective neurostimulators generically named bioelectronic medicines seems within reach. A sub-class of such devices is meant to monitor and treat impaired functions by intercepting, analyzing and modulating neural signals involved in the regulation of such functions using just one neural interface for those purposes. The primary objective of this review is to provide a first broad perspective on this type of single-interface devices for bioelectronic therapies. For this purpose, the concept, clinical applications and preclinical studies for further developments with such devices are here analyzed in a narrative manner.

Regional Differences in Sympathetic Nerve Activity Are Generated by Multiple Arterial Baroreflex Loops Arranged in Parallel

In this review, by evaluating the responses during freezing, rapid eye movement (REM) sleep, and treadmill exercise, we discuss how multiple baroreflex loops arranged in parallel act on different organs to modulate sympathetic nerve activity (SNA) in a region-specific and coordinated manner throughout the body. During freezing behaviors, arterial pressure (AP) remains unchanged, heart rate (HR) persistently decreases, renal SNA (RSNA) increases, and lumbar SNA (LSNA) remains unchanged. The baroreflex curve for RSNA shifts upward; that for LSNA remains unchanged; and that for HR shifts to the left. These region-specific changes in baroreflex curves are responsible for the region-specific changes in RSNA, LSNA, and HR during freezing. The decreased HR could allow the heart to conserve energy, which is offset by the increased RSNA caused by decreased vascular conductance, resulting in an unchanged AP. In contrast, the unchanged LSNA leaves the muscles in readiness for fight or flight. During REM sleep, AP increases, RSNA and HR decrease, while LSNA is elevated. The baroreflex curve for RSNA during REM sleep is vertically compressed in comparison with that during non-REM sleep. Cerebral blood flow is elevated while cardiac output is decreased during REM sleep. To address this situation, the brain activates the LSNA selectively, causing muscle vasoconstriction, which overcomes vasodilation of the kidneys as a result of the decreased RSNA and cardiac output. Accordingly, AP can be maintained during REM sleep. During treadmill exercise, AP, HR, and RSNA increase simultaneously. The baroreflex curve for RSNA shifts right-upward with the increased feedback gain, allowing maintenance of a stable AP with significant fluctuations in the vascular conductance of working muscles. Thus, the central nervous system may employ behavior-specific scenarios for modulating baroreflex loops for differential control of SNA, changing the SNA in a region-specific and coordinated manner, and then optimizing circulatory regulation corresponding to different behaviors.

Closed-Loop Vagus Nerve Stimulation for the Treatment of Cardiovascular Diseases: State of the Art and Future Directions

The autonomic nervous system exerts a fine beat-to-beat regulation of cardiovascular functions and is consequently involved in the onset and progression of many cardiovascular diseases (CVDs). Selective neuromodulation of the brain-heart axis with advanced neurotechnologies is an emerging approach to corroborate CVDs treatment when classical pharmacological agents show limited effectiveness. The vagus nerve is a major component of the cardiac neuroaxis, and vagus nerve stimulation (VNS) is a promising application to restore autonomic function under various pathological conditions. VNS has led to encouraging results in animal models of CVDs, but its translation to clinical practice has not been equally successful, calling for more investigation to optimize this technique. Herein we reviewed the state of the art of VNS for CVDs and discuss avenues for therapeutic optimization. Firstly, we provided a succinct description of cardiac vagal innervation anatomy and physiology and principles of VNS. Then, we examined the main clinical applications of VNS in CVDs and the related open challenges. Finally, we presented preclinical studies that aim at overcoming VNS limitations through optimization of anatomical targets, development of novel neural interface technologies, and design of efficient VNS closed-loop protocols.

Measures of cardiovascular function suggest autonomic nervous system dysregulation after surgical induction of joint injury in the male Lewis rat

OBJECTIVES

Functional changes in the autonomic nervous system may help explain variability in the progression of knee osteoarthritis (OA). Thus, the objective of this study was to evaluate autonomic nervous system shifts, measured via heart rate response variables, in rat knee joint injury and OA models.

METHODS

Cardiovascular characteristics were measured at baseline and bi-weekly for 8 weeks after skin incision, medial collateral ligament transection (MCLT), or MCLT+medial meniscus transection (MCLT+MMT). Heart rate was also assessed during a mild stressor (elevated maze). At endpoint, cardiovascular responses to mechanical knee stimuli were evaluated, as well as responses to 1-phenylbiguanide, a 5HT_3A receptor agonist with reported ability to stimulate vagal responses.

RESULTS

During low activity, a slower heart rate occurred in MCLT (299 ± 10 bpm) and MCLT+MMT (310 ± 10 bpm) animals compared to controls (325 ± 10 bpm). Furthermore, patellar ligament mechanical stimuli produced an immediate decrease in heart rate and blood pressure in all groups. Finally, a larger drop in heart rate was observed in MCLT (252 ± 40 bpm) and MCLT+MMT (263 ± 49 bpm) following administration of 1-phenylbiguanide compared to skin incision (168 ± 45 bpm).

CONCLUSIONS

Acute mechanical stimulation of the patellar ligament produced drops in heart rate, suggesting a possible joint-brain connection that modulates autonomic responses. With both joint injury, cardiac vagal activation was altered in response to pharmacological stimulation, with chronic longitudinal heart rate reduction. These data provide some preliminary evidence of potential functional shifts in autonomic nervous system function in models of joint injury and OA.

Seeing Is Believing: Making Wellbeing More Tangible

Positive Psychology has been instrumental in promoting wellbeing science in the modern era. However, there are still ways in which positive psychology interventions and positive education programmes can be improved to achieve more robust and sustained effects. One suggested method is to make wellbeing more salient and tangible through the use of objective tools that assess the relationship between psychological and physiological wellbeing, and enable wellbeing status and change to be seen. With the addition of an interdisciplinary team, as well as technology-enabled and pedagogically sound learning tools and approaches, the potential for positive outcomes and impact increases exponentially. Monitoring wellbeing progress in this way can provide evidence, motivation and belief in positive psychology and wellbeing interventions. This can lead to engaged learning, sustained benefits and systemic impact. Positive psychology needs to strategically extend on the emerging work in this field to help everyone, including policy makers, notice and value wellbeing.

The indirect impact of heart rate variability on cold pressor pain tolerance and intensity through psychological distress in individuals with chronic pain: the Tromsø Study

Supplemental Digital Content is Available in the Text. The hypoalgesic impact of cardiovascular regulatory systems on evoked pain responsiveness in those with chronic pain is conveyed via the indirect effects of psychological distress.

Introduction:

Chronic pain (CP) patients often display lower heart rate variability (HRV) and baroreceptor sensitivity (BRS), which are associated with increased evoked pain intensity and decreased pain tolerance.

Objective:

The purpose of this study was to test whether the association between low levels of HRV and BRS and increased evoked pain responsiveness in individuals with CP is mediated by psychological distress and whether this mediation is sex dependent.

Methods:

The sample consisted of 877 participants in Wave 6 of the Tromsø population study who reported clinically meaningful CP. Resting HRV and BRS parameters were derived from continuous beat-to-beat blood pressure recordings. Psychological distress was assessed using the Hopkins Symptom Checklist-10. After cardiovascular assessment, participants completed a 106-second cold pressor task (3°C bath), which assessed cold pressor pain intensity (CPI) and cold pressor pain tolerance (CPT).

Results:

In the full CP sample, mediation analyses showed significant indirect effects, without direct effects, of HRV and BRS on both CPT and CPI via psychological distress. When stratified by sex, significant indirect effects via psychological distress were only found in males for the impact of rMSSD on CPT, the impact of SDNN on CPT, and the impact of BRS on CPT via psychological distress. Moderated mediation analyses revealed that there were no significant sex differences in the indirect effects of HRV and BRS on both CPT and CPI via psychological distress.

Conclusions:

The hypoalgesic impact of cardiovascular regulatory systems on evoked pain responses is conveyed via the indirect effects of psychological distress.

Decoding Vagus-Nerve Activity with Carbon Nanotube Sensors in Freely Moving Rodents

The vagus nerve is the largest autonomic nerve and a major target of stimulation therapies for a wide variety of chronic diseases. However, chronic recording from the vagus nerve has been limited, leading to significant gaps in our understanding of vagus nerve function and therapeutic mechanisms. In this study, we use a carbon nanotube yarn (CNTY) biosensor to chronically record from the vagus nerves of freely moving rats for over 40 continuous hours. Vagal activity was analyzed using a variety of techniques, such as spike sorting, spike-firing rates, and interspike intervals. Many spike-cluster-firing rates were found to correlate with food intake, and the neural-firing rates were used to classify eating and other behaviors. To our knowledge, this is the first chronic recording and decoding of activity in the vagus nerve of freely moving animals enabled by the axon-like properties of the CNTY biosensor in both size and flexibility and provides an important step forward in our ability to understand spontaneous vagus-nerve function.

Prolonged QT intervals in mice with cardiomyocyte-specific deficiency of the molecular clock

AIM

Cardiac arrhythmias and sudden deaths have diurnal rhythms in humans. The underlying mechanisms are unknown. Mice with cardiomyocyte-specific disruption of the molecular clock genes have lower heart rate than control. Because changes in the QT interval on the electrocardiogram is a clinically used marker of risk of arrhythmias, we sought to test if the biological rhythms of QT intervals are dependent on heart rate and if this dependency is changed when the molecular clock is disrupted.

METHODS

We implanted radio transmitters in male mice with cardiomyocyte-specific Bmal1 knockout (CBK) and in control mice and recorded 24-h ECGs under diurnal and circadian conditions. We obtained left ventricular monophasic action potentials during pacing in hearts ex vivo.

RESULTS

Both RR and QT intervals were longer in conscious CBK than control mice (RR: 117 ± 7 vs 110 ± 9 ms, P < .05; and QT: 53 ± 4 vs 48 ± 2 ms, P < .05). The prolonged QT interval was independent of the slow heart rate in CBK mice. The QT interval exhibited diurnal and circadian rhythms in both CBK and control mice. The action potential duration was longer in CBK than in control mice, indicating slower repolarization. Action potential alternans occurred at lower pacing rate in hearts from CBK than control mice (12 ± 3 vs 16 ± 2 Hz, respectively, P < .05).

CONCLUSION

The bradycardic CBK mice have prolonged ventricular repolarization independent of the heart rate. Diurnal and circadian rhythms in repolarization are preserved in CBK mice and are not a consequence of the 24-h rhythm in heart rate. Arrhythmia vulnerability appears to be increased when the cardiac clock is disrupted.

The Heart in the Mind: A Systematic Review and Meta-Analysis of the Association Between Theory of Mind and Cardiac Vagal Tone

Theory of mind (ToM) is the human ability to infer the mental states of others in order to understand their behaviors and plan own actions. In the past decades, accumulating evidence has shown that heart rate variability (HRV), an index of parasympathetic control of the heart, is linked to behavioral regulation, social competence, and social cognition abilities, all implicated-to some extent-in ToM. This study aims to systematically review and meta-analyze the available studies, investigating the relation between ToM and HRV in typically developing people. Six studies were eligible for the meta-analysis, yielding a significant association between HRV and ToM of a small-to-medium effect size (g = 0.44). This result was not influenced by publication bias. Due to the small number of studies eligible for the meta-analysis, it was not possible to test for the effect of categorical moderators. The moderating role of sex and quality of the studies was examined by meta-regression analysis. Moderation analysis did not yield any significant effect; however, at a descriptive level, studies yielding the largest effect size were characterized by the use of high frequency-HRV assessment at rest and the Reading the Mind in the Eyes Test to evaluate ToM abilities. The results preliminarily suggest that tonic HRV might be used as an indicator of the ability to understand the content of mind of others.

Auricular Vagus Neuromodulation-A Systematic Review on Quality of Evidence and Clinical Effects

Background: The auricular branch of the vagus nerve runs superficially, which makes it a favorable target for non-invasive stimulation techniques to modulate vagal activity. For this reason, there have been many early-stage clinical trials on a diverse range of conditions. These trials often report conflicting results for the same indication. Methods: Using the Cochrane Risk of Bias tool we conducted a systematic review of auricular vagus nerve stimulation (aVNS) randomized controlled trials (RCTs) to identify the factors that led to these conflicting results. The majority of aVNS studies were assessed as having "some" or "high" risk of bias, which makes it difficult to interpret their results in a broader context. Results: There is evidence of a modest decrease in heart rate during higher stimulation dosages, sometimes at above the level of sensory discomfort. Findings on heart rate variability conflict between studies and are hindered by trial design, including inappropriate washout periods, and multiple methods used to quantify heart rate variability. There is early-stage evidence to suggest aVNS may reduce circulating levels and endotoxin-induced levels of inflammatory markers. Studies on epilepsy reached primary endpoints similar to previous RCTs testing implantable vagus nerve stimulation therapy. Preliminary evidence shows that aVNS ameliorated pathological pain but not evoked pain. Discussion: Based on results of the Cochrane analysis we list common improvements for the reporting of results, which can be implemented immediately to improve the quality of evidence. In the long term, existing data from aVNS studies and salient lessons from drug development highlight the need for direct measures of local neural target engagement. Direct measures of neural activity around the electrode will provide data for the optimization of electrode design, placement, and stimulation waveform parameters to improve on-target engagement and minimize off-target activation. Furthermore, direct measures of target engagement, along with consistent evaluation of blinding success, must be used to improve the design of controls-a major source of concern identified in the Cochrane analysis. The need for direct measures of neural target engagement and consistent evaluation of blinding success is applicable to the development of other paresthesia-inducing neuromodulation therapies and their control designs.

Therapeutic Potential of Vagus Nerve Stimulation for Inflammatory Bowel Diseases

The vagus nerve is a mixed nerve, comprising 80% afferent fibers and 20% efferent fibers. It allows a bidirectional communication between the central nervous system and the digestive tract. It has a dual anti-inflammatory properties via activation of the hypothalamic pituitary adrenal axis, by its afferents, but also through a vago-vagal inflammatory reflex involving an afferent (vagal) and an efferent (vagal) arm, called the cholinergic anti-inflammatory pathway. Indeed, the release of acetylcholine at the end of its efferent fibers is able to inhibit the release of tumor necrosis factor (TNF) alpha by macrophages via an interneuron of the enteric nervous system synapsing between the efferent vagal endings and the macrophages and releasing acetylcholine. The vagus nerve also synapses with the splenic sympathetic nerve to inhibit the release of TNF-alpha by splenic macrophages. It can also activate the spinal sympathetic system after central integration of its afferents. This anti-TNF-alpha effect of the vagus nerve can be used in the treatment of chronic inflammatory bowel diseases, represented by Crohn’s disease and ulcerative colitis where this cytokine plays a key role. Bioelectronic medicine, via vagus nerve stimulation, may have an interest in this non-drug therapeutic approach as an alternative to conventional anti-TNF-alpha drugs, which are not devoid of side effects feared by patients.