Internal senses of the vagus nerve

Roseburia intestinalis-derived butyrate alleviates neuropathic pain

Approximately 20% of patients with shingles develop postherpetic neuralgia (PHN). We investigated the role of gut microbiota in shingle- and PHN-related pain. Patients with shingles or PHN exhibited significant alterations in their gut microbiota with microbial markers predicting PHN development among patients with shingles. Functionally, fecal microbiota transplantation from patients with PHN to mice heightened pain sensitivity. Administration of Roseburia intestinalis, a bacterium both depleted in patients with shingles and PHN, alleviated peripheral nerve injury-induced pain in mice. R. intestinalis enhanced vagal neurotransmission to the nucleus tractus solitarius (NTS) to suppress the central amygdala (CeA), a brain region involved in pain perception. R. intestinalis-generated butyrate activated vagal neurons through the receptor, G protein-coupled receptor 41 (GPR41). Vagal knockout of Gpr41 abolished the effects of R. intestinalis on the NTS-CeA circuit and reduced pain behaviors. Overall, we established a microbiota-based model for PHN risk assessment and identified R. intestinalis as a potential pain-alleviating probiotic.

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential environmental dangers. However, this function can be detrimental during allergic reactions, as vagal nociceptors contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we investigate the changes in the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identify a specific class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of allergic airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the neuropeptide Y (NPY) receptor Npy1r. A screening of cytokines and neurotrophins reveals that interleukin 1β (IL-1β), IL-13, and brain-derived neurotrophic factor (BDNF) drive part of this reprogramming. IL-13 triggers Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, NPY is released into the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells reveals that a cell-specific knockout of NPY1R in nociceptor neurons in asthmatic mice altered T cell infiltration. Opposite findings are observed in asthmatic mice in which nociceptor neurons are chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits the activity of nociceptor neurons.

The gut microbiome and the brain

PURPOSE OF REVIEW

The importance of the gut microbiome for human health and well-being is generally accepted, and elucidating the signaling pathways between the gut microbiome and the host offers novel mechanistic insight into the (patho)physiology and multifaceted aspects of healthy aging and human brain functions.

RECENT FINDINGS

The gut microbiome is tightly linked with the nervous system, and gut microbiota are increasingly emerging as important regulators of emotional and cognitive performance. They send and receive signals for the bidirectional communication between gut and brain via immunological, neuroanatomical, and humoral pathways. The composition of the gut microbiota and the spectrum of metabolites and neurotransmitters that they release changes with increasing age, nutrition, hypoxia, and other pathological conditions. Changes in gut microbiota (dysbiosis) are associated with critical illnesses such as cancer, cardiovascular, and chronic kidney disease but also neurological, mental, and pain disorders, as well as chemotherapies and antibiotics affecting brain development and function.

SUMMARY

Dysbiosis and a concomitant imbalance of mediators are increasingly emerging both as causes and consequences of diseases affecting the brain. Understanding the microbiota's role in the pathogenesis of these disorders will have major clinical implications and offer new opportunities for therapeutic interventions.

Sensory neuroimmune interactions at the barrier

Epithelial barriers such as the skin, lung, and gut, in addition to having unique physiologic functions, are designed to preserve tissue homeostasis upon challenge with a variety of allergens, irritants, or pathogens. Both the innate and adaptive immune systems play a critical role in responding to epithelial cues triggered by environmental stimuli. However, the mechanisms by which organs sense and coordinate complex epithelial, stromal, and immune responses have remained a mystery. Our increasing understanding of the anatomic and functional characteristics of the sensory nervous system is greatly advancing a new field of peripheral neuroimmunology and subsequently changing our understanding of mucosal immunology. Herein, we detail how sensory biology is informing mucosal neuroimmunology, even beyond neuroimmune interactions seen within the central and autonomic nervous systems.

The peripheral neuroimmune system

Historically, the nervous and immune systems were studied as separate entities. The nervous system relays signals between the body and the brain by processing sensory inputs and executing motor outputs, whereas the immune system provides protection against injury and infection through inflammation. However, recent developments have demonstrated that these systems mount tightly integrated responses. In particular, the peripheral nervous system acts in concert with the immune system to control reflexes that maintain and restore homeostasis. Notwithstanding their homeostatic mechanisms, dysregulation of these neuroimmune interactions may underlie various pathological conditions. Understanding how these two distinct systems communicate is an emerging field of peripheral neuroimmunology that promises to reveal new insights into tissue physiology and identify novel targets to treat disease.

Defining cardioception: Heart-brain crosstalk

Interoception, the sensation and perception of internal bodily states, should be conceptualized through specialized modalities like cardioception, pulmoception, gastroception, and uroception. This NeuroView emphasizes cardioception, exploring heart-brain interactions, cardiac reflexes, and their influence on mental states and behavior.

The vagus nerve: An old but new player in brain-body communication

The vagus nerve is a crucial component of the parasympathetic nervous system, facilitating communication between the brain and various organs, including the ears, heart, lungs, pancreas, spleen, and gastrointestinal tract. The caudal nucleus of the solitary tract in the brainstem is the initial site regulated by the vagus nerve in brain-body communication, including the interactions with immune system. Increasing evidence suggests that the gut-brain axis, via the vagus nerve, may play a role in the development and progression of psychiatric, neurologic, and inflammation-related disorders. Population-based cohort studies indicate that truncal vagotomy may reduce the risk of neurological disorders such as Parkinson's disease and Alzheimer's disease, underscoring the vagus nerve's significance in these conditions. Given its role in the cholinergic anti-inflammatory pathway, α7 nicotinic acetylcholine receptors present a potential therapeutic target. Additionally, noninvasive transcutaneous auricular vagus nerve stimulation (taVNS) shows promise as a therapeutic tool for these disorders. This article provides a historical review of the vagus nerve and explores its role in brain-body communication. Finally, we discuss future directions, including the potential of noninvasive taVNS as a therapeutic approach.

Lateralized nodose ganglia gene expression implicates cholecystokinin receptors in interoceptive reward signaling

The vagus nerves are important carriers of sensory information from the viscera to the central nervous system. Emerging evidence suggests that sensory signaling through the right, but not the left, vagus nerve evokes striatal dopamine release and reinforces appetitive behaviors. However, the extent to which differential gene expression within vagal sensory neurons contributes to this asymmetric reward-related signaling remains unknown. Here, we use single-cell RNA sequencing to identify genes that are differentially expressed between the left and right nodose ganglia (NG) to identify candidate genes likely to contribute to vagus-mediated reward signaling. We find that a group of neurons expressing Chrna3 (nicotinic acetylcholine receptor subunit 3) and Cckar (cholecystokinin A receptor) is preferentially expressed in the right NG of both rats and mice. This result suggests that differential expression of gut-innervating nutrient sensors in NG neurons may contribute to asymmetric encoding of interoceptive rewards by the vagus nerves.

Position-independent functional refinement within the vagus motor topographic map

Motor neurons in the central nervous system often lie in a continuous topographic map, where neurons that innervate different body parts are spatially intermingled. This is the case for the efferent neurons of the vagus nerve, which innervate diverse muscle and organ targets in the head and viscera for brain-body communication. It remains elusive how neighboring motor neurons with different fixed peripheral axon targets develop the separate somatodendritic (input) connectivity they need to generate spatially precise body control. Here, we show that vagus motor neurons in the zebrafish indeed generate spatially appropriate peripheral responses to focal sensory stimulation even when they are transplanted into ectopic positions within the topographic map, indicating that circuit refinement occurs after the establishment of coarse topography. Refinement depends on motor neuron synaptic transmission, suggesting that an experience-dependent periphery-to-brain feedback mechanism establishes specific input connectivity among intermingled motor populations.

Brain-body physiology: Local, reflex, and central communication

Behavior is tightly synchronized with bodily physiology. Internal needs from the body drive behavior selection, while optimal behavior performance requires a coordinated physiological response. Internal state is dynamically represented by the nervous system to influence mood and emotion, and body-brain signals also direct responses to external sensory cues, enabling the organism to adapt and pursue its goals within an ever-changing environment. In this review, we examine the anatomy and function of the brain-body connection, manifested across local, reflex, and central regulation levels. We explore these hierarchical loops in the context of the immune system, specifically through the lens of immunoception, and discuss the impact of its dysregulation on human health.

Bridging brain and body in cancer

Recent work has highlighted the central role the brain-body axis plays in not only maintaining organismal homeostasis but also coordinating the body's response to immune and inflammatory insults. Here, we discuss how science is poised to address the many ways that our brain is directly involved with disease. In particular, we feel that combining cutting-edge tools in neuroscience with translationally relevant models of cancer will be critical to understanding how the brain and tumors communicate and modulate each other's behavior.

Serotonergic modulation of swallowing in a complete fly vagus nerve connectome

How the body interacts with the brain to perform vital life functions, such as feeding, is a fundamental issue in physiology and neuroscience. Here, we use a whole-animal scanning transmission electron microscopy volume of Drosophila to map the neuronal circuits that connect the entire enteric nervous system to the brain via the insect vagus nerve at synaptic resolution. We identify a gut-brain feedback loop in which Piezo-expressing mechanosensory neurons in the esophagus convey food passage information to a cluster of six serotonergic neurons in the brain. Together with information on food value, these central serotonergic neurons enhance the activity of serotonin receptor 7-expressing motor neurons that drive swallowing. This elemental circuit architecture includes an axo-axonic synaptic connection from the glutamatergic motor neurons innervating the esophageal muscles onto the mechanosensory neurons that signal to the serotonergic neurons. Our analysis elucidates a neuromodulatory sensory-motor system in which ongoing motor activity is strengthened through serotonin upon completion of a biologically meaningful action, and it may represent an ancient form of motor learning.

Neurophysiological Basis of Electroacupuncture Stimulation in the Treatment of Cardiovascular-Related Diseases: Vagal Interoceptive Loops

PURPOSE

The vagal sensory nerve (VSN) is an essential interoceptive pathway that is connected to every level of the body. Its intricate genetic coding provides sustenance for physiological processes, including controlling blood pressure and respiration. Electroacupuncture (EA) is a proven surface stimulation therapy that can regulate vagal nerve activity, which can effectively prevent cardiovascular diseases. A growing number of studies have concentrated on the mapping of VSN codes, but little is known, and the physiological background of how EA influences interoceptive has not been fully explored.

METHOD

Here, we incorporate the hypothesized interaction among EA targets, VSNs, and the heart. This offers suggestions for using a versatile and focused EA strategy to modify vagal interoceptive awareness to enhance cardiovascular conditions. We first clarified the major role of vagal nerve in the control of cardiac activity. Additionally, we clarified the multidimensional coding pattern in the VSNs, revealing that the targeted control of multimodal interoceptive is the functional basis of the synchronization of cardiovascular system.

FINDING

We propose a strategy in which EA of the VSNs is employed to activate the interoceptive loop and reduce the risk of cardiovascular disease.

Self-Adhesive and Self-Sustainable Bioelectronic Patch for Physiological Feedback Electronic Modulation of Soft Organs

Bionic electrical stimulation (Bio-ES) aims to achieve personalized therapy and proprioceptive adaptation by mimicking natural neural signatures of the body, while current Bio-ES devices are reliant on complex sensing and computational simulation systems, thus often limited by the low-fidelity of simulated electrical signals, and failure of interface information interaction due to the mechanical mismatch between soft tissues and rigid electrodes. Here, the study presents a flexible and ultrathin self-sustainable bioelectronic patch (Bio-patch), which can self-adhere to the lesion area of organs and generate bionic electrical signals synchronized vagal nerve envelope in situ to implement Bio-ES. It allows adaptive adjustment of intensity, frequency, and waveform of the Bio-ES to fully meet personalized needs of tissue regeneration based on real-time feedback from the vagal neural controlled organs. With this foundation, the Bio-patch can effectively intervene with excessive fibrosis and microvascular stasis during the natural healing process by regulating the polarization time of macrophages, promoting the reconstruction of the tissue-engineered structure, and accelerating the repair of damaged liver and kidney. This work develops a practical approach to realize biomimetic electronic modulation of the growth and development of soft organs only using a multifunctional Bio-patch, which establishes a new paradigm for precise bioelectronic medicine.

Dynamics of heterogeneous Hopfield neural network with adaptive activation function based on memristor

Memristor and activation function are two important nonlinear factors of the memristive Hopfield neural network. The effects of different memristors on the dynamics of Hopfield neural networks have been studied by many researchers. However, less attention has been paid to the activation function. In this paper, we present a heterogeneous memristive Hopfield neural network with neurons using different activation functions. The activation functions include fixed activation functions and an adaptive activation function, where the adaptive activation function is based on a memristor. The theoretical and experimental study of the neural network's dynamics has been conducted using phase portraits, bifurcation diagrams, and Lyapunov exponents spectras. Numerical results show that complex dynamical behaviors such as multi-scroll chaos, transient chaos, state jumps and multi-type coexisting attractors can be observed in the heterogeneous memristive Hopfield neural network. In addition, the hardware implementation of memristive Hopfield neural network with adaptive activation function is designed and verified. The experimental results are in good agreement with those obtained using numerical simulations.

Multi-level exploration of auricular acupuncture: from traditional Chinese medicine theory to modern medical application

As medical research advances and technology rapidly develops, auricular acupuncture has emerged as a point of growing interest. This paper delves into the intricate anatomy of auricular points, their significance and therapeutic principles in traditional Chinese medicine (TCM), and the underlying mechanisms of auricular acupuncture in contemporary medicine. The aim is to delve deeply into this ancient and mysterious medical tradition, unveiling its multi-layered mysteries in the field of neurostimulation. The anatomical structure of auricular points is complex and delicate, and their unique neurovascular network grants them a special status in neurostimulation therapy. Through exploration of these anatomical features, we not only comprehend the position of auricular points in TCM theory but also provide a profound foundation for their modern medical applications. Through systematic review, we synthesize insights from traditional Chinese medical theory for modern medical research. Building upon anatomical and classical theoretical foundations, we focus on the mechanisms of auricular acupuncture as a unique neurostimulation therapy. This field encompasses neuroregulation, pain management, psychological wellbeing, metabolic disorders, and immune modulation. The latest clinical research not only confirms the efficacy of auricular stimulation in alleviating pain symptoms and modulating metabolic diseases at the endocrine level but also underscores its potential role in regulating patients' psychological wellbeing. This article aims to promote a comprehensive understanding of auricular acupuncture by demonstrating its diverse applications and providing substantial evidence to support its broader adoption in clinical practice.

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential dangers in the environment. However, this function can be detrimental during allergic reactions, since vagal nociceptors can contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance, in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we aimed to investigate the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identified a unique class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the NPY receptor Npy1r. A screening of cytokines and neurotrophins revealed that IL-1β, IL-13 and BDNF drive part of this reprogramming. IL-13 triggered Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, sympathetic neurons and macrophages release NPY in the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells has revealed that a cell-specific knockout of Npy1r in nociceptor neurons in asthmatic mice leads to an increase in airway inflammation mediated by T cells. Opposite findings were observed in asthmatic mice in which nociceptor neurons were chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits nociceptor neurons' activity.

Noninvasive closed-loop acoustic brain-computer interface for seizure control

Rationale: The brain-computer interface (BCI) is core tasks in comprehensively understanding the brain, and is one of the most significant challenges in neuroscience. The development of novel non-invasive neuromodulation technique will drive major innovations and breakthroughs in the field of BCI. Methods: We develop a new noninvasive closed-loop acoustic brain-computer interface (aBCI) for decoding the seizure onset based on the electroencephalography and triggering ultrasound stimulation of the vagus nerve to terminate seizures. Firstly, we create the aBCI system and decode the onset of seizure via a multi-level threshold model based on the analysis of wireless-collected electroencephalogram (EEG) signals recorded from above the hippocampus. Then, the different acoustic parameters induced acoustic radiation force were used to stimulate the vagus nerve in a rat model of epilepsy-induced by pentylenetetrazole. Finally, the results of epileptic EEG signal triggering ultrasound stimulation of the vagus nerve to control seizures. In addition, the mechanism of aBCI control seizures were investigated by real-time quantitative polymerase chain reaction (RT-qPCR). Results: In a rat model of epilepsy, the aBCI system selectively actives mechanosensitive neurons in the nodose ganglion while suppressing neuronal excitability in the hippocampus and amygdala, and stops seizures rapidly upon ultrasound stimulation of the vagus nerve. Physical transection or chemical blockade of the vagus nerve pathway abolish the antiepileptic effects of aBCI. In addition, aBCI shows significant antiepileptic effects compared to conventional vagus nerve electrical stimulation in an acute experiment. Conclusions: Closed-loop aBCI provides a novel, safe and effective tool for on-demand stimulation to treat abnormal neuronal discharges, opening the door to next generation non-invasive BCI.

A gut-brain-gut interoceptive circuit loop gates sugar ingestion in Drosophila

The communication between the brain and digestive tract is critical for optimising nutrient preference and food intake, yet the underlying neural mechanisms remain poorly understood1-7. Here, we show that a gut-brain-gut circuit loop gates sugar ingestion in flies. We discovered that brain neurons regulating food ingestion, IN18, receive excitatory input from enteric sensory neurons, which innervate the oesophagus and express the sugar receptor Gr43a. These enteric sensory neurons monitor the sugar content of food within the oesophagus during ingestion and send positive feedback signals to IN1s, stimulating the consumption of high-sugar foods. Connectome analyses reveal that IN1s form a core ingestion circuit. This interoceptive circuit receives synaptic input from enteric afferents and provides synaptic output to enteric motor neurons, which modulate the activity of muscles at the entry segments of the crop, a stomach-like food storage organ. While IN1s are persistently activated upon ingestion of sugar-rich foods, enteric motor neurons are continuously inhibited, causing the crop muscles to relax and enabling flies to consume large volumes of sugar. Our findings reveal a key interoceptive mechanism that underlies the rapid sensory monitoring and motor control of sugar ingestion within the digestive tract, optimising the diet of flies across varying metabolic states.

The immunology of sickness metabolism

Everyone knows that an infection can make you feel sick. Although we perceive infection-induced changes in metabolism as a pathology, they are a part of a carefully regulated process that depends on tissue-specific interactions between the immune system and organs involved in the regulation of systemic homeostasis. Immune-mediated changes in homeostatic parameters lead to altered production and uptake of nutrients in circulation, which modifies the metabolic rate of key organs. This is what we experience as being sick. The purpose of sickness metabolism is to generate a metabolic environment in which the body is optimally able to fight infection while denying vital nutrients for the replication of pathogens. Sickness metabolism depends on tissue-specific immune cells, which mediate responses tailored to the nature and magnitude of the threat. As an infection increases in severity, so do the number and type of immune cells involved and the level to which organs are affected, which dictates the degree to which we feel sick. Interestingly, many alterations associated with metabolic disease appear to overlap with immune-mediated changes observed following infection. Targeting processes involving tissue-specific interactions between activated immune cells and metabolic organs therefore holds great potential for treating both people with severe infection and those with metabolic disease. In this review, we will discuss how the immune system communicates in situ with organs involved in the regulation of homeostasis and how this communication is impacted by infection.

Vagal TRPV1 + sensory neurons regulate myeloid cell dynamics and protect against influenza virus infection

Influenza viruses are a major global cause of morbidity and mortality. Vagal TRPV1 + nociceptive sensory neurons, which innervate the airways, are known to mediate defenses against harmful agents. However, their function in lung antiviral defenses remains unclear. Our study reveals that both systemic and vagal-specific ablation of TRPV1 + nociceptors reduced survival in mice infected with influenza A virus (IAV), despite no significant changes in viral burden or weight loss. Mice lacking nociceptors showed exacerbated lung pathology and elevated levels of pro-inflammatory cytokines. The increased mortality was not attributable to the loss of the TRPV1 ion channel or neuropeptides CGRP or substance P. Immune profiling through flow cytometry and single-cell RNA sequencing identified significant nociceptor deficiency-mediated changes in the lung immune landscape, including an expansion of neutrophils and monocyte-derived macrophages. Transcriptional analysis revealed impaired interferon signaling in these myeloid cells and an imbalance in distinct neutrophil sub-populations in the absence of nociceptors. Furthermore, anti-GR1-mediated depletion of myeloid cells during IAV infection significantly improved survival, underscoring a role of nociceptors in preventing pathogenic myeloid cell states that contribute to IAV-induced mortality. One Sentence Summary : TRPV1 + neurons facilitate host survival from influenza A virus infection by controlling myeloid cell responses and immunopathology.

Navigating internal senses: A road map for the vagal interoceptive system

A road map for the vagal interoceptive system.

Non-invasive ventral cervical magnetoneurography as a proxy of in vivo lipopolysaccharide-induced inflammation

Maintenance of autonomic homeostasis is continuously calibrated by sensory fibers of the vagus nerve and sympathetic chain that convey compound action potentials (CAPs) to the central nervous system. Lipopolysaccharide (LPS) intravenous challenge reliably elicits a robust inflammatory response that can resemble systemic inflammation and acute endotoxemia. Here, we administered LPS intravenously in nine healthy subjects while recording ventral cervical magnetoneurography (vcMNG)-derived CAPs at the rostral Right Nodose Ganglion (RNG) and the caudal Right Carotid Artery (RCA) with optically pumped magnetometers (OPM). We observed vcMNG RNG and RCA neural firing rates that tracked changes in TNF-α levels in the systemic circulation. Further, endotype subgroups based on high and low IL-6 responders segregate RNG CAP frequency (at 30-120 min) and based on high and low IL-10 response discriminate RCA CAP frequency (at 0-30 min). These vcMNG tools may enhance understanding and management of the neuroimmune axis that can guide personalized treatment based on an individual's distinct endophenotype.

The Effect of In-Ear and Behind-Ear Transcutaneous Auricular Vagus Nerve Stimulation on Autonomic Function: A Randomized, Single-Blind, Sham-Controlled Study

Background/Objectives: Transcutaneous auricular vagus nerve stimulation (TaVNS) is a non-invasive method of electrical stimulation used to autonomic neuromodulation. Position and form of the electrodes are important for the effectiveness of autonomic modulation. This study was aimed to investigate the effect of TaVNS in-ear and behind-ear on autonomic variables. Methods: A total of 76 healthy participants (male: 40, female: 36) were randomized into four groups as in-ear TaVNS, behind-ear TaVNS, in-ear sham, and behind-ear sham. The TaVNS protocol included bilateral auricular stimulation for 20 min, 25 hertz frequency, a pulse width of 250 μs, and a suprathreshold current (0.13-50 mA). Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), and heart rate variability (HRV) were measured baseline and after stimulation. The parameters RMSSD (root mean square of consecutive differences between normal heartbeats), LF power (low-frequency), and HF power (high-frequency) were assessed in the HRV analysis. Results: HR decreased in the in-ear TaVNS after intervention (p < 0.05), but did not change in behind-ear TaVNS and sham groups compared to baseline (p > 0.05). SBP and DBP decreased and RMSSD increased in the in-ear and behind-ear TaVNS groups (p < 0.05), but did not change in sham groups compared to baseline (p > 0.05). There was no significant difference in LF and HF power after TaVNS compared to baseline in all groups (p > 0.05). SBP was lower and RMSSD was higher in-ear TaVNS than behind-ear TaVNS after intervention (p < 0.05). Conclusions: In-ear TaVNS appears to be more effective than behind-ear TaVNS in modulating SBP and RMSSD, but this needs to be studied in larger populations.

Molecular Characterization of Nodose Ganglia Development Reveals a Novel Population of Phox2b+ Glial Progenitors in Mice

The vagal ganglia, comprised of the superior (jugular) and inferior (nodose) ganglia of the vagus nerve, receive somatosensory information from the head and neck or viscerosensory information from the inner organs, respectively. Developmentally, the cranial neural crest gives rise to all vagal glial cells and to neurons of the jugular ganglia, while the epibranchial placode gives rise to neurons of the nodose ganglia. Crest-derived nodose glial progenitors can additionally generate autonomic neurons in the peripheral nervous system, but how these progenitors generate neurons is unknown. Here, we found that some Sox10+ neural crest-derived cells in, and surrounding, the nodose ganglion transiently expressed Phox2b, a master regulator of autonomic nervous system development, during early embryonic life. Our genetic lineage-tracing analysis in mice of either sex revealed that despite their common developmental origin and extreme spatial proximity, a substantial proportion of glial cells in the nodose, but not in the neighboring jugular ganglia, have a history of Phox2b expression. We used single-cell RNA-sequencing to demonstrate that these progenitors give rise to all major glial subtypes in the nodose ganglia, including Schwann cells, satellite glia, and glial precursors, and mapped their spatial distribution by in situ hybridization. Lastly, integration analysis revealed transcriptomic similarities between nodose and dorsal root ganglia glial subtypes and revealed immature nodose glial subtypes. Our work demonstrates that these crest-derived nodose glial progenitors transiently express Phox2b, give rise to the entire complement of nodose glial cells, and display a transcriptional program that may underlie their bipotent nature.

The wolf in sheep's clothing: vasovagal syncope in acute aortic dissection

BACKGROUND

The presentation of acute aortic dissection can pose a challenge for emergency physicians, as it may occur without pain. Atypical presentations can lead to significant delays in diagnosis and increased mortality rates.

CASE DESCRIPTION

Our case illustrates that isolated painless syncope can be a rare presenting symptom of acute aortic dissection type A. What is unique about our case is the limited extension of the dissection tear and the availability of Holter monitoring during the syncopal episode.

CONCLUSION

This constellation provides insight into the pathophysiological mechanism of the syncope in this patient. Mechanisms of syncope related to acute aortic dissection are diverse. We show that vasovagal activation not related to pain can be the underlying mechanism of syncope in acute aortic dissection type A. Although excessive vasovagal tone in the setting of aortic dissection has been hypothesized in the past, it has never been as clearly illustrated as in the present case. This also highlights the challenge in risk stratification of syncope in the emergency department.

Neural circuits for taste sensation

The sense of taste arises from the detection of chemicals in food by taste buds, the peripheral cellular detectors for taste. Although numerous studies have extensively investigated taste buds, research on neural circuits from primary taste neurons innervating taste buds to the central nervous system has only recently begun owing to recent advancements in neuroscience research tools. This minireview focuses primarily on recent reports utilizing advanced neurogenetic tools across relevant brain regions.

The Brain-Heart Network of Syncope

Observed and recorded in various forms since ancient times, 'syncope' is often popularly called 'fainting', such that the two terms are used synonymously. Syncope/fainting can be caused by a variety of conditions, including but not limited to head injuries, vertigo, and oxygen deficiency. Here, we draw on a large body of literature on syncope, including the role of a recently discovered set of specialized mammalian neurons. Although the etiology of syncope still remains a mystery, we have attempted to provide a comprehensive account of what is known and what still needs to be performed. Much of our understanding of syncope is owing to studies in the laboratory mouse, whereas evidence from human patients remains scarce. Interestingly, the cardioinhibitory Bezold-Jarisch reflex, recognized in the early 1900s, has an intriguing similarity to-and forms the basis of-syncope. In this review, we have integrated this minimal model into the modern view of the brain-neuron-heart signaling loop of syncope, to which several signaling events contribute. Molecular signaling is our major focus here, presented in terms of a normal heart, and thus, syncope due to abnormal or weak heart activity is not discussed in detail. In addition, we have offered possible directions for clinical intervention based on this model. Overall, this article is expected to generate interest in chronic vertigo and syncope/fainting, an enigmatic condition that affects most humans at some point in life; it is also hoped that this may lead to a mechanism-based clinical intervention in the future.

Hypotussic cough in persons with dysphagia: biobehavioral interventions and pathways to clinical implementation

Cough is a powerful, protective expulsive behavior that assists in maintaining respiratory health by clearing foreign material, pathogens, and mucus from the airways. Therefore, cough is critical to survival in both health and disease. Importantly, cough protects the airways and lungs from both antegrade (e.g., food, liquid, saliva) and retrograde (e.g., bile, gastric acid) aspirate contents. Aspiration is often the result of impaired swallowing (dysphagia), which allows oral and/or gastric contents to enter the lung, especially in individuals who also have cough dysfunction (dystussia). Cough hyposensitivity, downregulation, or desensitization- collectively referred to as hypotussia- is common in individuals with dysphagia, and increases the likelihood that aspirated material will reach the lung. The consequence of hypotussia with reduced airway clearance can include respiratory tract infection, chronic inflammation, and long-term damage to the lung parenchyma. Despite the clear implications for health, the problem of managing hypotussia in individuals with dysphagia is frequently overlooked. Here, we provide an overview of the current interventions and treatment approaches for hypotussic cough. We synthesize the available literature to summarize research findings that advance our understanding of these interventions, as well as current gaps in knowledge. Further, we highlight pragmatic resources to increase awareness of hypotussic cough interventions and provide support for the clinical implementation of evidence-based treatments. In culmination, we discuss potential innovations and future directions for hypotussic cough research.

Krause corpuscles are genital vibrotactile sensors for sexual behaviours

Krause corpuscles, which were discovered in the 1850s, are specialized sensory structures found within the genitalia and other mucocutaneous tissues1-4. The physiological properties and functions of Krause corpuscles have remained unclear since their discovery. Here we report the anatomical and physiological properties of Krause corpuscles of the mouse clitoris and penis and their roles in sexual behaviour. We observed a high density of Krause corpuscles in the clitoris compared with the penis. Using mouse genetic tools, we identified two distinct somatosensory neuron subtypes that innervate Krause corpuscles of both the clitoris and penis and project to a unique sensory terminal region of the spinal cord. In vivo electrophysiology and calcium imaging experiments showed that both Krause corpuscle afferent types are A-fibre rapid-adapting low-threshold mechanoreceptors, optimally tuned to dynamic, light-touch and mechanical vibrations (40-80 Hz) applied to the clitoris or penis. Functionally, selective optogenetic activation of Krause corpuscle afferent terminals evoked penile erection in male mice and vaginal contraction in female mice, while genetic ablation of Krause corpuscles impaired intromission and ejaculation of males and reduced sexual receptivity of females. Thus, Krause corpuscles of the clitoris and penis are highly sensitive mechanical vibration detectors that mediate sexually dimorphic mating behaviours.

A body-brain circuit that regulates body inflammatory responses

The body-brain axis is emerging as a principal conductor of organismal physiology. It senses and controls organ function1,2, metabolism3 and nutritional state4-6. Here we show that a peripheral immune insult strongly activates the body-brain axis to regulate immune responses. We demonstrate that pro-inflammatory and anti-inflammatory cytokines communicate with distinct populations of vagal neurons to inform the brain of an emerging inflammatory response. In turn, the brain tightly modulates the course of the peripheral immune response. Genetic silencing of this body-brain circuit produced unregulated and out-of-control inflammatory responses. By contrast, activating, rather than silencing, this circuit affords neural control of immune responses. We used single-cell RNA sequencing, combined with functional imaging, to identify the circuit components of this neuroimmune axis, and showed that its selective manipulation can effectively suppress the pro-inflammatory response while enhancing an anti-inflammatory state. The brain-evoked transformation of the course of an immune response offers new possibilities in the modulation of a wide range of immune disorders, from autoimmune diseases to cytokine storm and shock.

Interoceptive signals from the heart and coronary circulation in health and disease

This review considers interoceptive signalling from the heart and coronary circulation. Vagal and cardiac sympathetic afferent sensory nerve endings are distributed throughout the atria, ventricles (mainly left), and coronary artery. A small proportion of cardiac receptors attached to thick myelinated vagal afferents are tonically active during the cardiac cycle. Dependent upon location, these mechanoreceptors detect fluctuations in atrial volume and coronary arterial perfusion. Atrial volume and coronary arterial signals contribute to beat-to-beat feedback control and physiological homeostasis. Most cardiac receptors are attached to thinly myelinated or nonmyelinated C fibres, many of which are unresponsive to the cardiac cycle. Of these, there are many chemically sensitive cardiac receptors which are activated during myocardial stress by locally released endogenous substances. In contrast, some tonically inactive receptors become activated by irregular ventricular wall mechanics or by distortion of the ischaemic myocardium. Furthermore, some are excited both by chemical mediators of ischaemia and wall abnormalities. Reflex responses arising from cardiac receptors attached to thinly myelinated or nonmyelinated are complex. Impulses that project centrally through vagal afferents elicit sympathoinhibition and hypotension, whereas impulses travelling in cardiac sympathetic afferents and spinal pathways elicit sympathoexcitation and hypertension. Two opposing cardiac reflexes may provide a mechanism for fine-tuning a composite haemodynamic response during myocardial stress. Sympathetic afferents provide the primary pathway for transmission of cardiac nociception to the central nervous system. However, activation of sympathetic afferents may increase susceptibility to life-threatening arrhythmias. Notably, the cardiac sympathetic afferent reflex predominates in pathophysiological states including hypertension and heart failure.

Interoceptive training impacts the neural circuit of the anterior insula cortex

Interoception is the perception of afferent information that arises from anywhere and everywhere within the body. Recently, interoceptive accuracy could be enhanced by cognitive training. Given that the anterior insula cortex (AIC) is a key node of interoception, we hypothesized that resting functional connectivity (RSFC) from AIC was involved in an effect of interoceptive training. To address this issue, we conducted a longitudinal intervention study using interoceptive training and obtained RSFC using fMRI before and after the intervention. A heartbeat perception task evaluated interoceptive accuracy. Twenty-two healthy volunteers (15 females, age 19.9 ± 2.0 years) participated. After the intervention, interoceptive accuracy was enhanced, and anxiety levels and somatic symptoms were reduced. Also, RSFC from AIC to the dorsolateral prefrontal cortex (DLPFC), superior marginal gyrus (SMG), anterior cingulate cortex (ACC), and brain stem, including nucleus tractus solitarius (NTS) were enhanced, and those from AIC to the visual cortex (VC) were decreased according to enhanced interoceptive accuracy. The neural circuit of AIC, ACC, and NTS is involved in the bottom-up process of interoception. The neural circuit of AIC, DLPFC, and SMG is involved in the top-down process of interoception, which was thought to represent the cognitive control of emotion. The findings provided a better understanding of neural underpinnings of the effect of interoceptive training on somatic symptoms and anxiety levels by enhancing both bottom-up and top-down processes of interoception, which has a potential contribution to the structure of psychotherapies based on the neural mechanism of psychosomatics.

Immunohistochemical localization of proteins involved in exocytosis of glutamate from P2X3 purinoceptor-expressing subserosal afferent nerve endings in the rat gastric antrum

We previously reported the presence of P2X3 purinoceptors (P2X3)-expressing subserosal afferent nerve endings consisting of net- and basket-like nerve endings in the rat gastric antrum. These nerve endings may morphologically be vagal mechanoreceptors activated by antral peristalsis. The present study investigated immunoreactivities for vesicular glutamate transporter (VGLUT) 1 and VGLUT2 as well as exocytosis-related proteins, i.e., core components of the SNARE complex (SNAP25, Stx1, and VAMP2) and synaptotagmin-1 (Syt1), in whole-mount preparations of the rat gastric antrum using double immunofluorescence. VGLUT1 immunoreactivity was not detected, whereas VGLUT2 immunoreactivity was observed in P2X3-immunoreactive subserosal nerve endings composed of both net- and basket-like endings. In net-like nerve endings, intense VGLUT2 immunoreactivity was localized in polygonal bulges of reticular nerve fibers and peripheral axon terminals. Furthermore, intense immunoreactivities for SNAP25, Stx1, and VAMP2 were localized in net-like nerve endings. Intense immunoreactivities for VAMP2 and Syt1 were observed in VGLUT2-immunoreactive net-like nerve endings. In basket-like nerve endings, VGLUT2 immunoreactivity was localized in pleomorphic terminal structures and small bulges surrounding the subserosal ganglion, whereas immunoreactivities for SNAP25, Stx1, and VAMP2 were weak in these nerve endings. VGLUT2-immunoreactive basket-like nerve endings were weakly immunoreactive for VAMP2 and Syt1. These results suggest that subserosal afferent nerve endings release glutamate by exocytosis mainly from net-like nerve endings to modulate their mechanoreceptor function.

Peripheral peroxisomal β-oxidation engages neuronal serotonin signaling to drive stress-induced aversive memory in C. elegans

Physiological dysfunction confers negative valence to coincidental sensory cues to induce the formation of aversive associative memory. How peripheral tissue stress engages neuromodulatory mechanisms to form aversive memory is poorly understood. Here, we show that in the nematode C. elegans, mitochondrial disruption induces aversive memory through peroxisomal β-oxidation genes in non-neural tissues, including pmp-4/very-long-chain fatty acid transporter, dhs-28/3-hydroxylacyl-CoA dehydrogenase, and daf-22/3-ketoacyl-CoA thiolase. Upregulation of peroxisomal β-oxidation genes under mitochondrial stress requires the nuclear hormone receptor NHR-49. Importantly, the memory-promoting function of peroxisomal β-oxidation is independent of its canonical role in pheromone production. Peripheral signals derived from the peroxisomes target NSM, a critical neuron for memory formation under stress, to upregulate serotonin synthesis and remodel evoked responses to sensory cues. Our genetic, transcriptomic, and metabolomic approaches establish peroxisomal lipid signaling as a crucial mechanism that connects peripheral mitochondrial stress to central serotonin neuromodulation in aversive memory formation.

Neuroendocrine cells initiate protective upper airway reflexes

Airway neuroendocrine (NE) cells have been proposed to serve as specialized sensory epithelial cells that modulate respiratory behavior by communicating with nearby nerve endings. However, their functional properties and physiological roles in the healthy lung, trachea, and larynx remain largely unknown. In this work, we show that murine NE cells in these compartments have distinct biophysical properties but share sensitivity to two commonly aspirated noxious stimuli, water and acid. Moreover, we found that tracheal and laryngeal NE cells protect the airways by releasing adenosine 5'-triphosphate (ATP) to activate purinoreceptive sensory neurons that initiate swallowing and expiratory reflexes. Our work uncovers the broad molecular and biophysical diversity of NE cells across the airways and reveals mechanisms by which these specialized excitable cells serve as sentinels for activating protective responses.

Position-independent functional refinement within the vagus motor topographic map

Motor neurons in the central nervous system often lie in a continuous topographic map, where neurons that innervate different body parts are spatially intermingled. This is the case for the efferent neurons of the vagus nerve, which innervate diverse muscle and organ targets in the head and viscera for brain-body communication. It remains elusive how neighboring motor neurons with different fixed peripheral axon targets develop the separate somatodendritic (input) connectivity they need to generate spatially precise body control. Here we show that vagus motor neurons in the zebrafish indeed generate spatially appropriate peripheral responses to focal sensory stimulation even when they are transplanted into ectopic positions within the topographic map, indicating that circuit refinement occurs after the establishment of coarse topography. Refinement depends on motor neuron synaptic transmission, suggesting that an experience-dependent periphery-to-brain feedback mechanism establishes specific input connectivity amongst intermingled motor populations.

Navigating the blurred path of mixed neuroimmune signaling

Evolution has created complex mechanisms to sense environmental danger and protect tissues, with the nervous and immune systems playing pivotal roles. These systems work together, coordinating local and systemic reflexes to restore homeostasis in response to tissue injury and infection. By sharing receptors and ligands, they influence the pathogenesis of various diseases. Recently, a less-explored aspect of neuroimmune communication has emerged: the release of neuropeptides from immune cells and cytokines/chemokines from sensory neurons. This article reviews evidence of this unique neuroimmune interplay and its impact on the development of allergy, inflammation, itch, and pain. We highlight the effects of this neuroimmune signaling on vital processes such as host defense, tissue repair, and inflammation resolution, providing avenues for exploration of the underlying mechanisms and therapeutic potential of this signaling.

Neuroimmune recognition and regulation in the respiratory system

Neuroimmune recognition and regulation in the respiratory system is a complex and highly coordinated process involving interactions between the nervous and immune systems to detect and respond to pathogens, pollutants and other potential hazards in the respiratory tract. This interaction helps maintain the health and integrity of the respiratory system. Therefore, understanding the complex interactions between the respiratory nervous system and immune system is critical to maintaining lung health and developing treatments for respiratory diseases. In this review, we summarise the projection distribution of different types of neurons (trigeminal nerve, glossopharyngeal nerve, vagus nerve, spinal dorsal root nerve, sympathetic nerve) in the respiratory tract. We also introduce several types of cells in the respiratory epithelium that closely interact with nerves (pulmonary neuroendocrine cells, brush cells, solitary chemosensory cells and tastebuds). These cells are primarily located at key positions in the respiratory tract, where nerves project to them, forming neuroepithelial recognition units, thus enhancing the ability of neural recognition. Furthermore, we summarise the roles played by these different neurons in sensing or responding to specific pathogens (influenza, severe acute respiratory syndrome coronavirus 2, respiratory syncytial virus, human metapneumovirus, herpes viruses, Sendai parainfluenza virus, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Staphylococcus aureus, amoebae), allergens, atmospheric pollutants (smoking, exhaust pollution), and their potential roles in regulating interactions among different pathogens. We also summarise the prospects of bioelectronic medicine as a third therapeutic approach following drugs and surgery, as well as the potential mechanisms of meditation breathing as an adjunct therapy.

Development and regeneration of the vagus nerve

The vagus nerve, with its myriad constituent axon branches and innervation targets, has long been a model of anatomical complexity in the nervous system. The branched architecture of the vagus nerve is now appreciated to be highly organized around the topographic and/or molecular identities of the neurons that innervate each target tissue. However, we are only just beginning to understand the developmental mechanisms by which heterogeneous vagus neuron identity is specified, patterned, and used to guide the axons of particular neurons to particular targets. Here, we summarize our current understanding of the complex topographic and molecular organization of the vagus nerve, the developmental basis of neuron specification and patterned axon guidance that supports this organization, and the regenerative mechanisms that promote, or inhibit, the restoration of vagus nerve organization after nerve damage. Finally, we highlight key unanswered questions in these areas and discuss potential strategies to address these questions.

The gut-brain axis and cognitive control: A role for the vagus nerve

Survival requires the integration of external information and interoceptive cues to effectively guide advantageous behaviors, particularly foraging and other behaviors that promote energy acquisition and consumption. The vagus nerve acts as a critical relay between the abdominal viscera and the brain to convey metabolic signals. This review synthesizes recent findings from rodent models and humans revealing the impact of vagus nerve signaling from the gut on the control of higher-order neurocognitive domains, including anxiety, depression, reward motivation, and learning and memory. We propose a framework where meal consumption engages gastrointestinal tract-originating vagal afferent signaling that functions to alleviate anxiety and depressive-like states, while also promoting motivational and memory functions. These concurrent processes serve to favor the encoding of meal-relevant information into memory storage, thus facilitating future foraging behaviors. Modulation of these neurocognitive domains by vagal tone is also discussed in the context of pathological conditions, including the use of transcutaneous vagus nerve stimulation for the treatment of anxiety disorders, major depressive disorder, and dementia-associated memory impairments. Collectively, these findings highlight the contributions of gastrointestinal vagus nerve signaling to the regulation of neurocognitive processes that shape various adaptive behavioral responses.

Vagal sensory pathway for the gut-brain communication

The communication between the gut and brain is crucial for regulating various essential physiological functions, such as energy balance, fluid homeostasis, immune response, and emotion. The vagal sensory pathway plays an indispensable role in connecting the gut to the brain. Recently, our knowledge of the vagal gut-brain axis has significantly advanced through molecular genetic studies, revealing a diverse range of vagal sensory cell types with distinct peripheral innervations, response profiles, and physiological functions. Here, we review the current understanding of how vagal sensory neurons contribute to gut-brain communication. First, we highlight recent transcriptomic and genetic approaches that have characterized different vagal sensory cell types. Then, we focus on discussing how different subtypes encode numerous gut-derived signals and how their activities are translated into physiological and behavioral regulations. The emerging insights into the diverse cell types and functional properties of vagal sensory neurons have paved the way for exciting future directions, which may provide valuable insights into potential therapeutic targets for disorders involving gut-brain communication.

The vagus nerve in cardiovascular physiology and pathophysiology: From evolutionary insights to clinical medicine

The parasympathetic nervous system via the vagus nerve exerts profound influence over the heart. Together with the sympathetic nervous system, the parasympathetic nervous system is responsible for fine-tuned regulation of all aspects of cardiovascular function, including heart rate, rhythm, contractility, and blood pressure. In this review, we highlight vagal efferent and afferent innervation of the heart, with a focus on insights from comparative biology and advances in understanding the molecular and genetic diversity of vagal neurons, as well as interoception, parasympathetic dysfunction in heart disease, and the therapeutic potential of targeting the parasympathetic nervous system in cardiovascular disease.

Molecular cell types as functional units of the efferent vagus nerve

The vagus nerve vitally connects the brain and body to coordinate digestive, cardiorespiratory, and immune functions. Its efferent neurons, which project their axons from the brainstem to the viscera, are thought to comprise "functional units" - neuron populations dedicated to the control of specific vagal reflexes or organ functions. Previous research indicates that these functional units differ from one another anatomically, neurochemically, and physiologically but have yet to define their identity in an experimentally tractable way. However, recent work with genetic technology and single-cell genomics suggests that genetically distinct subtypes of neurons may be the functional units of the efferent vagus. Here we review how these approaches are revealing the organizational principles of the efferent vagus in unprecedented detail.

Selective KCNQ2/3 Potassium Channel Opener ICA-069673 Inhibits Excitability in Mouse Vagal Sensory Neurons

Heightened excitability of vagal sensory neurons in inflammatory visceral diseases contributes to unproductive and difficult-to-treat neuronally based symptoms such as visceral pain and dysfunction. Identification of targets and modulators capable of regulating the excitability of vagal sensory neurons may lead to novel therapeutic options. KCNQ1-KCNQ5 genes encode KV7.1-7.5 potassium channel α-subunits. Homotetrameric or heterotetrameric KV7.2-7.5 channels can generate the so-called M-current (IM) known to decrease the excitability of neurons including visceral sensory neurons. This study aimed to address the hypothesis that KV7.2/7.3 channels are key regulators of vagal sensory neuron excitability by evaluating the effects of KCNQ2/3-selective activator, ICA-069673, on IM in mouse nodose neurons and determining its effects on excitability and action potential firings using patch clamp technique. The results showed that ICA-069673 enhanced IM density, accelerated the activation, and delayed the deactivation of M-channels in a concentration-dependent manner. ICA-069673 negatively shifted the voltage-dependent activation of IM and increased the maximal conductance. Consistent with its effects on IM, ICA-069673 induced a marked hyperpolarization of resting potential and reduced the input resistance. The hyperpolarizing effect was more pronounced in partially depolarized neurons. Moreover, ICA-069673 caused a 3-fold increase in the minimal amount of depolarizing current needed to evoke an action potential, and significantly limited the action potential firings in response to sustained suprathreshold stimulations. ICA-069673 had no effect on membrane currents when Kcnq2 and Kcnq3 were deleted. These results indicate that opening KCNQ2/3-mediated M-channels is sufficient to suppress the excitability and enhance spike accommodation in vagal visceral sensory neurons. SIGNIFICANCE STATEMENT: This study supports the hypothesis that selectively activating KCNQ2/3-mediated M-channels is sufficient to suppress the excitability and action potential firings in vagal sensory neurons. These results provide evidence in support of further investigations into the treatment of various visceral disorders that involve nociceptor hyperexcitability with selective KCNQ2/3 M-channel openers.

Mechanisms for survival: vagal control of goal-directed behavior

Survival is a fundamental physiological drive, and neural circuits have evolved to prioritize actions that meet the energy demands of the body. This fine-tuning of goal-directed actions based on metabolic states ('allostasis') is deeply rooted in our brain, and hindbrain nuclei orchestrate the vital communication between the brain and body through the vagus nerve. Despite mounting evidence for vagal control of allostatic behavior in animals, its broader function in humans is still contested. Based on stimulation studies, we propose that the vagal afferent pathway supports transitions between survival modes by gating the integration of ascending bodily signals, thereby regulating reward-seeking. By reconceptualizing vagal signals as catalysts for goal-directed behavior, our perspective opens new avenues for theory-driven translational work in mental disorders.