Microbiota-gut-brain axis refers to a bidirectional communication between the gut microbiota and the brain. Alterations in this bidirectional signaling have been associated with multiple physiological and pathological processes.

The paper states: "The microbiota, the gut, and the brain communicate through the **microbiota-gut-brain axis** in a **bidirectional** way that involves the autonomic nervous system." It explains that the vagus nerve "is able to sense the microbiota metabolites through its afferents, to transfer this gut information to the central nervous system where it is integrated in the central autonomic network, and then to generate an adapted or inappropriate response." It concludes that "the role of the vagus nerve in microbiota-brain communication is now **well-established**."

The gut–brain axis (GBA) refers to the bidirectional communication network that links the central nervous system with the enteric nervous system, integrating neural, hormonal, and immunological signaling between the gut and the brain. This axis involves the autonomic nervous system, the hypothalamic–pituitary–adrenal axis, the immune system, and the gut microbiota. Increasing evidence indicates that the GBA plays a crucial role in regulating stress response, mood, and cognitive functions, suggesting that alterations in this system may contribute to the pathophysiology of various mental health disorders.

The authors describe "the microbiota-gut-brain (MGB) axis" as a system in which "accumulating evidence from animal and clinical studies has revealed that gut microbiota play important roles in various neurological diseases." They note that "the ENS can be reasonably regarded as the bridge between the intestinal microbiota and the nervous system" and that "the individual components of the MGB axis communicate with each other bi-directionally" through the autonomic nervous system, neuroendocrine signaling, and the hypothalamic-pituitary-adrenal axis. The paper explains that microbial products, immune signaling, and metabolites such as short-chain fatty acids can directly activate the enteric nervous system and influence both ENS and CNS neurochemistry.

The gut-brain axis theory is based on experimental evidence indicating a link between the gut environment and the central nervous system. The paper describes this as bidirectional communication between the gastrointestinal tract and the brain.

This review defines the "microbiota–gut–brain axis" as "a complex, **bidirectional communication network** linking the central nervous system and the gastrointestinal tract." It notes that this communication occurs "through neural (vagus nerve and enteric nervous system), endocrine (HPA axis), immune, and metabolic pathways," and that gut microbes produce "neurotransmitters and neuroactive metabolites" that can affect brain function and behavior.

The gut microbiota–brain axis is a complex bidirectional communication system between the gut microbiota and the central nervous system. It comprises neural (vagus nerve and enteric nervous system), endocrine (hypothalamic–pituitary–adrenal axis and enteroendocrine signaling), immune, and metabolic pathways. Through these routes, gut microbes and their metabolites can influence blood–brain barrier integrity, neuroinflammation, neurotransmitter systems, and behavior, while the brain in turn modulates gut motility, secretion, and microbial composition.

The microbiome–gut–brain axis (mGBA) represents a bidirectional communication network that connects the gastrointestinal tract and its microbial inhabitants with the central nervous system. This axis integrates neural, endocrine, immune, and metabolic signaling pathways, allowing gut microorganisms to influence brain development, neurogenesis, and synaptic plasticity, as well as behavior and cognition. Conversely, the brain can affect gut physiology and microbiota composition through autonomic nervous system output and stress-related hormonal changes.

The authors state that "the **gut microbiota–brain axis** is a **bidirectional communication** system between the gastrointestinal tract and the central nervous system." They explain that "the vagus nerve can be activated by the gut microbiota, transmitting information from the gastrointestinal tract to the nucleus tractus solitarius" in the brainstem, and that vagal signaling participates in "regulation of mood, behavior, and inflammation." The review emphasizes that this axis is mediated by "neural, immune, and endocrine mechanisms."

This article notes that "the **vagus nerve** and the central nervous and immune systems are responsible for the connection between the brain and gut microbiome." It describes the gut–brain axis as "a **two-way communication system**" in which signals travel from the gut to the brain via "vagal afferents, circulating metabolites, and immune mediators" and from the brain to the gut via "autonomic efferents and neuroendocrine pathways." The authors discuss how disturbances of this axis are associated with neurological and psychiatric disorders.

The microbiota–gut–brain axis is defined as the bidirectional communication network that links the intestinal microbiota with the central nervous system, involving neural, endocrine, and immune-mediated pathways. Experimental studies using germ-free animals, antibiotics, and fecal microbiota transplantation have demonstrated that alterations in gut microbiota composition can affect brain development, neurotransmission, and behavior. These findings support a causal role for gut microbes in modulating brain function via defined biological routes, rather than a purely correlative association.

The review defines the "microbiome-intestine-brain axis" as "a **two-way communication pathway** between the gut microbiome, the gastrointestinal tract, and the peripheral and central nervous systems." It states that the ways they interact "include the **vagus nerve**, the endocrine, and the immune systems" and that the vagus nerve "can detect microbiota metabolites via its afferents, transferring this gut information to the CNS." The paper adds that a cholinergic anti‑inflammatory pathway via the vagus nerve can reduce peripheral inflammation and intestinal permeability.

The gut–brain axis comprises a complex network of bidirectional communication between the gastrointestinal tract and the brain, including the enteric nervous system, the vagus nerve, the hypothalamic–pituitary–adrenal axis, and immune signaling. Preclinical studies have shown that manipulation of the gut microbiome can alter anxiety-like and depressive-like behaviors, while clinical studies indicate that patients with mood disorders often exhibit dysbiosis of the gut microbiota. Together, these data support the gut–brain axis as a biologically grounded system linking gut physiology and microbial composition to central nervous system function.

The concept of the brain–gut–microbiome axis describes a bidirectional communication system that involves the central nervous system, the enteric nervous system, and the gut microbiota. This axis operates through multiple biological pathways, including neural (vagal and spinal afferents), endocrine (such as cortisol and gut peptides), immune, and microbial metabolic routes. Altered signaling along this axis has been implicated in irritable bowel syndrome, inflammatory bowel disease, anxiety, depression, and other disorders, indicating that the brain–gut–microbiome axis has concrete physiological and pathophysiological relevance.

This peer‑reviewed article explains that "intestinal microbes are known to impact the development of the CNS through the brain-gut axis" and that "the ENS can be reasonably regarded as the bridge between the intestinal microbiota and the nervous system." It describes the ENS as a "complete sensorimotor reflex circuit" that coordinates gut functions and notes that components of the microbiota–gut–brain axis "communicate with each other bi-directionally" via the autonomic nervous system, hypothalamic-pituitary-adrenal axis, and neuroendocrine signaling. The authors detail mechanisms including immune and enteroendocrine signaling, neuropod-mediated transmission from enteroendocrine cells to sensory neurons, and microbial metabolites (e.g., short-chain fatty acids, polyamines) that influence ENS and CNS neuronal signaling.

In this review, Mayer (2011) writes that "a growing body of literature supports the concept of continuous bidirectional communication between the brain and the gut, which is regulated at neural, hormonal and immunological levels" and that this system is often referred to as the brain–gut axis. The article describes how the central nervous system influences gastrointestinal functions through the autonomic nervous system and HPA axis, while visceral afferent pathways, immune mediators, and enteroendocrine signaling convey information from the gut to the brain. It also highlights the role of gut microbiota in modulating brain function and behavior, suggesting that the gut–brain axis is a real biological communication network integrating neural, endocrine and immune mechanisms.

The microbiota–gut–brain axis (MGBA) is a term used to describe the bidirectional communication between the gut microbiota and the central nervous system, including the brain and spinal cord. This communication involves the autonomic nervous system, the enteric nervous system, neuroendocrine signaling, and immune pathways. Evidence from animal models and human studies indicates that the MGBA regulates gut physiology, brain development, behavior, and stress responses, establishing it as a real biological system rather than a purely theoretical construct.

The concept of a microbiota–gut–brain axis encompasses the idea that gut microorganisms can signal to the brain and thereby influence behavior and neurological function. Mechanistically, this axis involves neural pathways such as the vagus nerve, microbial metabolites including short-chain fatty acids, tryptophan metabolites and bile acids, as well as immune mediators and neuroendocrine factors. Experimental manipulation of the gut microbiota has been shown to change brain chemistry and behavior in animal models, providing evidence for a functional biological communication system.

Cryan et al. describe the "microbiome–gut–brain axis" as "a bidirectional communication system between the central nervous system and the gastrointestinal tract" that includes the enteric nervous system, autonomic nervous system, neuroendocrine and neuroimmune pathways, and the gut microbiota. They state that this axis "plays a key role in maintaining homeostasis" and that perturbations are linked to a range of neurological and psychiatric conditions. Mechanisms discussed include vagus nerve signaling, microbial production of neurotransmitters and short-chain fatty acids, modulation of barrier integrity, and immune activation, all of which provide concrete biological routes for gut–brain communication.

The gut-brain connection is complex and bidirectional. Signals pass both ways between your digestive system and central nervous system, and health or disease in one can affect the other.

In this animal study, the authors report that transcutaneous auricular vagus nerve stimulation (taVNS) "significantly alleviated depression-like behaviors" in chronically stressed rats and that taVNS "reshaped the gut microbiota" by increasing some bacterial taxa and reducing others. They note that a positive correlation between a synaptic protein (Syngr1) in the hippocampus and specific Lactobacillus species "suggests that the **microbiota-gut-brain axis** may play a key role in the antidepressant effects of vagus nerve stimulation."

The gut-brain axis is the bidirectional communication system between the digestive tract and the brain. It involves a complex network of nerves and biochemicals.

In mainstream biomedical literature, the gut-brain axis is commonly described as a bidirectional communication network between the gastrointestinal tract and the central nervous system, mediated by neural, endocrine, immune, and metabolic pathways. This is a standard concept in neurogastroenterology and related fields.

Gut-brain axis is a term used to describe bidirectional signaling between the brain and a large portion of the gastrointestinal tract. The video explains that this is considered a biological system involving the autonomic nervous system, enteric nervous system, immune system, and neuroendocrine system.