Gut-Brain & Microbiome Learning Center · Module 4 of 12
The Vagus Nerve
Explains the vagus nerve and its role in bidirectional communication.
The gut-brain axis depends on multiple communication pathways. One of the neural pathways researchers study is the vagus nerve.
Within gut-brain research, the vagus nerve is important because it participates in communication between internal organs and the central nervous system. It is one part of a much larger network involving the enteric nervous system, immune signaling, hormones, microbial metabolites and other biological processes.
Part of a Two-Way Communication System
As introduced earlier in the NVL Learning Center, gut-brain communication is bidirectional. Signals can travel from the gastrointestinal system toward the brain and from the brain toward the gastrointestinal system.
These directions are often described as:
Afferent signaling
Information traveling from the gastrointestinal system and other parts of the body toward the brain.
Efferent signaling
Information traveling from the brain toward organs and tissues, including the gastrointestinal system.
The vagus nerve participates in this larger communication system.
The Gut Does More Than Receive Signals
The gastrointestinal system does not simply wait for instructions from the brain. Information originating within the intestinal environment can participate in signaling toward the central nervous system.
The legacy NVL research material describes afferent gut-to-brain communication as involving several types of biological information, including:
- enteroendocrine signaling
- immune signaling molecules
- metabolites
- gut-derived products
- neuroactive molecules
The vagus nerve is one pathway researchers investigate when studying how information from the gastrointestinal environment may be communicated toward the brain.
The Enteric Nervous System
The gastrointestinal tract also contains its own extensive neural network: the enteric nervous system. The enteric and central nervous systems participate in the larger gut-brain communication network.
Researchers therefore study relationships among:
- the intestinal environment
- enteric nervous system
- vagal signaling
- central nervous system
- microbial activity
These systems should not be viewed as isolated pathways.
Microbial Metabolites and Neural Signaling
Microorganisms within the gastrointestinal tract produce numerous metabolic products. Researchers investigate whether and how some microbial metabolites may interact with:
- intestinal cells
- immune cells
- metabolism
- the enteric nervous system
- afferent signaling pathways involving the vagus nerve
This does not mean that every microbial metabolite directly signals the brain through the vagus nerve. It means that vagal signaling is one of several biological pathways being investigated within microbiota-gut-brain research.
Explore Module 7 — Microbial MetabolitesWhy Researchers Study the Vagus Nerve
The vagus nerve provides researchers with one biological pathway through which the gastrointestinal system and brain can participate in communication. Understanding this pathway may help researchers better understand the larger gut-brain network.
The pathway is studied alongside immune signaling, neuroendocrine signaling, microbial metabolites and intestinal physiology.
What We Know
The gastrointestinal system and central nervous system participate in bidirectional communication. Neural pathways, including pathways involving the vagus nerve, are part of this communication system.
Gut-to-brain signaling and brain-to-gut signaling operate within a broader network of biological processes.
What Researchers Are Studying
Researchers continue to investigate how signals originating within the gastrointestinal environment interact with neural pathways.
Microbial activity, metabolites, immune signals and intestinal physiology are among the factors being studied in relation to gut-brain communication.
What Remains Uncertain
The existence of a gut-brain communication pathway does not establish that changes in that pathway cause autism. It also does not establish that altering vagal activity will change core autistic characteristics.
The role of vagal signaling within microbiome and neurodevelopmental research remains an area of continuing investigation.