Gastric network
The stomach has a pacemaker. Interstitial cells of Cajal generate a slow electrical rhythm at roughly 0.05 Hz (one cycle per 20 seconds, or ~3 cycles per minute) that coordinates peristalsis, and unlike the heart’s it never stops and never much changes rate. Rebollo et al. (2018) recorded that rhythm cutaneously with EGG during resting-state fMRI, and found that a distributed set of brain regions holds a constant phase lag to it.
That is a strange kind of network. Every other resting-state network is defined by regions correlating with each other. This one is defined by regions correlating with a stomach.
What is in it
After strict confound control the surviving map is:
- occipital cortex and precuneus
- bilateral insula
- pre- and postcentral gyri (somatomotor)
- cerebellar clusters
Rebollo & Tallon-Baudry (2022) characterize the network’s position on the cortical hierarchy: it sits in unimodal sensory and motor cortex rather than transmodal association cortex. That placement is theoretically loaded. If gastric coupling were a matter of interpreting bodily state, one would expect transmodal, anterior-insular or default-mode territory. Instead the stomach’s rhythm shows up where the brain does sensing and moving.
Note what this does not look like. It is not the lamina-i-spinothalamocortical-pathway interoceptive anatomy Craig described, and it is not the central-autonomic-network. Whether the gastric network is an interoceptive network at all, or a rhythm that entrains sensorimotor cortex for reasons unrelated to visceral perception, is unresolved — nobody has shown that anyone feels anything as a function of their gastric–brain coupling.
The size correction
The published extent of this network was, for five years, mostly artefact. Levakov et al. (2023) found that without regressing head motion and non-grey-matter signal, 19.89% of grey matter appears gastric-coupled; with them, 1.16% does. Prior work — Rebollo et al. (2018), Rebollo & Tallon-Baudry (2022), Choe et al. (2021), Müller et al. (2022) — used RETROICOR at best and none regressed motion.
The reason is not sloppiness but something more interesting: the confounds are themselves phase-locked to the stomach. CSF signal, global signal and three of six head-motion parameters synchronize with the EGG rhythm. The likely common cause is respiration, which moves the head and modulates the gastric signal at an overlapping frequency. In this literature motion is not noise added on top of signal; it is correlated with the thing being measured, which is the worst case.
Does the stomach cause it?
The best evidence is not human and not correlational:
- Vagotomy and hunger (rats). Cao et al. (2022) found a sensory/motor/limbic network coupled to gastric rhythm in head-fixed rats — motion cannot explain it — modulated by hunger state and substantially reduced by bilateral vagotomy. Cut the nerve, lose the coupling.
- Vagal stimulation (humans). Müller et al. (2022) found auricular taVNS increases stomach–brain coupling. See bioelectronic-medicine.
Together these make a reasonable case that the coupling is driven by ascending vagal traffic from the stomach rather than by shared physiological noise. It is the strongest causal story attached to any brain–body coupling measure in this wiki.
And yet it cannot be measured in a person
This is the tension the page exists to hold. Group-level, the network is real, replicable across labs and datasets, and causally supported. Individual-level, Levakov et al. found the coupling has no test–retest reliability (r ≈ −.14 to .08 across runs in the same people), while the EGG signal alone retested at r = .74 and the fMRI connectivity was strongly subject-identifiable.
A phenomenon can be robust at the group level and unmeasurable at the individual level, and the gastric network currently is both. That is fatal for the biomarker uses — predicting weight loss, eating pathology, IBS severity — and harmless for the existence claim. See is-brain-body-coupling-a-reliable-individual-difference.
Why the wiki should care about the stomach specifically
Three reasons, none of them about digestion.
- It is the channel where cross-modal coherence was originally claimed. Herbert et al. (2012) linked cardiac accuracy to gastric detection; Whitehead & Drescher (1980) to voluntary control of gastric motility. is-interoception-domain-general names gastric as the missing third axis in the decisive test — and Banellis et al. did not measure it.
- It is where spontaneous thought points. The brain-constrained CCA in banellis-2026-body-wandering put stomach at the top of its thought loadings (0.58), and body-wandering’s neural signature is thalamo-somatomotor — the same unimodal territory the gastric network occupies. Whether that is coincidence or the same phenomenon met from two directions is untested and cheap to test.
- It is a rhythm, not an event. Cardiac interoception is studied through discrete beats and heartbeat-evoked potentials. The gastric signal is a slow continuous oscillation with a stable individual frequency, which makes it the natural substrate for phase-based questions about how visceral timing organizes cortical activity — the kind of question the ERP tradition cannot ask.
Open
- Does gastric–brain coupling relate to anything a person experiences or reports? No study has connected it to a percept, a feeling, or a questionnaire.
- Is the surviving 1.16% the network, or the part of the network that survives a preprocessing choice? Without global signal regression the map is larger and more similar to prior work.
- Is there a gastric analogue of interoceptive accuracy at all — a perceptual task on this channel, as opposed to a coupling measure? interoceptive-control notes you cannot ask someone to drive their gastric motility; detection is a separate question, and largely a 1980s literature.