Interoceptive rhythms in the brain
A Nature Neuroscience review from Catherine Tallon-Baudry’s Paris lab (with Tahnée Engelen and Marco Solcà, first authors contributing equally) that reframes interoception around a single argument: the body’s rhythms are not a private interoceptive channel but a timing structure woven into how the brain processes everything, including the outside world. The heart beats, the lungs fill, the stomach contracts; all three send information up at rates fast enough to fluctuate with perception and cognition, and the review’s claim is that these rhythms shape exteroception, cognition and action rather than merely reporting bodily state.
This is the wiki’s most complete statement of the rhythm-based view of interoception, and it is the natural counterweight to the wiki’s dominant perception-based view (the heartbeat-detection tradition and its taxonomies). Where the counting-task literature asks how well a person perceives a beat, this review asks what each beat does to the rest of the brain whether or not it is perceived. Almost nothing here needs the participant to feel anything.
The organizing move: three rhythms, one integration problem
Tallon-Baudry’s programme has always studied cardiac and gastric signals as carrier rhythms rather than as sensations. The review generalizes that stance to respiration and states it as a thesis: interoception and exteroception are “tightly intertwined… at all stages,” so the natural unit of analysis is not the interoceptive channel but the interoceptive-exteroceptive interaction. The evolutionary argument for why this must be so is compact — because interoception relates to vital functions, it is likely to be “a driving force for exteroception, action and cognition”: foraging couples physiological need to sensory sampling of the environment, so reading the body and reading the world are two halves of one loop.
The three rhythms
Cardiac. Two lines of work. Cardiac cycle effects — perception, memory, action and emotion depend on whether an event falls in systole (baroreceptors firing, a relatively fixed brief window) or diastole. The pulsed inhibition hypothesis holds that baroreceptor activation at systole induces a generalized cortical inhibition; it is robust for pain (consistently reduced during systole) and mixed elsewhere. Separately, heartbeat-evoked responses index the cortical response to each beat and are the review’s richest single object — see below. The review is careful (Box 1) that both measures are shadowed by the cardiac field artifact and by the fact that stimulus timing within the cardiac cycle is often determined a posteriori, which can turn a subtle heart-rate difference into a spurious “cycle effect.”
Respiratory. The review’s respiration section is the same argument this wiki already carries on respiratory-interoception, from the same primary literature (Tort et al. 2018; Zelano et al. 2016): nasal respiration entrains limbic oscillations and modulates memory and emotional ratings, the preBötzinger complex generates the rhythm, and — uniquely — breathing is voluntarily controllable (Box 2), which makes it both a signal and an effector. What the review adds to the wiki’s existing treatment is breadth of coupling: respiration-locked activity appears in somatosensory, motor, visual and auditory cortex and across default/salience/dorsal-attention networks at rest, not only in the limbic system.
Gastric. The stomach’s ~0.05 Hz pacemaker rhythm couples to an extensive cortical network that — crucially for the review’s thesis — includes all exteroceptive cortices and motor regions but very few transmodal cognitive regions. The review floats the proposal (Rebollo & Tallon-Baudry) that the gastric rhythm orchestrates brain dynamics by bypassing higher-level regions, while noting it has not been experimentally tested. The wiki met this network through the papers that audited it (Levakov) and reached it by attention (Haruki & Ogawa); this review is the source those papers are arguing with.
The heartbeat-evoked response is the review’s centre of gravity
The HER gets the fullest treatment because it is where the three interpretive frameworks collide. The review lays out that the HER is modulated by attention to the heartbeat and has been related, in turn, to:
- Emotions — HER amplitude depends on the valence of emotional stimuli and on mood/arousal, reviving the somatic-marker intuition that cardiac afference colours feeling.
- Predictive coding — HERs reconceived not as sensory responses but as prediction errors signalling the discrepancy between predicted and observed cardiac signal; modulated by cardiac-driven prediction of external stimuli and by expected emotional content.
- The self — HERs index self-relatedness (they track self vs other in mental imagery), the strength of body ownership during bodily illusions, the stability of preference-based decisions, and — most strikingly — the subject of conscious experience: HER amplitude predicts conscious detection of near-threshold visual and somatosensory stimuli, and indexes residual consciousness in post-comatose patients.
The clinical hinge the wiki should carry: patients with depersonalization/derealization, who experience detachment from their own sensations, body and emotions, do not show the modulation of HERs by interoceptive attention. That is the review’s cleanest link from a neural rhythm to the felt bodily self — and it dovetails with embodied-selfhood and with Farb’s viscerosomatic momentary self.
The network, and what it is missing
Collapsed across all three rhythms (Fig. 3), the impacted cortical network is “spatially extensive, mostly consistent across the three rhythms.” It confirms the expected limbic interoceptive regions (insula — with no posterior/anterior distinction drawn — amygdala/hippocampus, cingulate) but adds two things the wiki should note:
- Sensory and motor cortices are in it. The respiratory and gastric rhythms couple to visual, auditory and (pre)motor cortex, whose anatomical link to interoception is unknown — possibly via intracortical projections, possibly subcortical (the PBN projects to sensory thalamic relays and has visceromotor links).
- The default-mode and salience hubs are in it, but cognitive prefrontal regions are not. The medial DMN nodes (vmPFC, PCC/precuneus) and the salience hubs (anterior insula, IFG) couple to bodily rhythms; “cognitive prefrontal regions appear quite disconnected from bodily rhythms.” So the body’s rhythms reach the brain’s connectivity hubs while sparing its executive cortex — a shape the review reads as consistent with interoception scaffolding self-related and integrative processing rather than deliberative thought.
Three candidate mechanisms (the theoretical payload)
The review’s most cited contribution is its side-by-side of how bodily rhythms might actually be integrated with brain dynamics (Fig. 4). All three are live; none is established.
- Oscillatory synchrony — the scaffolding hypothesis. Because the temporal structure of neural activity in different regions reflects the cardiac/respiratory/gastric rhythms, distant regions can be considered synchronized by the body. Bodily rhythms act as carrier waves imposing shared temporal windows of excitability, offering a common clock for binding distributed activity. Its weakness, which the review names: it is “relatively disconnected from actual bodily physiological states” — it uses the rhythm’s timing but not its content, so the bodily state per se does little work.
- Predictive coding, extended. Because rhythms are predictable, entrained oscillations can align optimal-processing phases with expected sensory input (strong for nasal respiration ↔ olfactory sampling); cycle effects become the exploitation of predictable visceral timing; and, scaled up, interoceptive prediction underwrites allostasis, emotion and the self (Barrett, Seth, Gu). This is the framework that connects the review to the wiki’s interoceptive-inference/active-inference thread and to Harrison et al.’s model-based test.
- Multisensory integration. Interoceptive and exteroceptive signals converge on shared neurons in a super-additive (or sub-additive) manner, as shown for cardiac and tactile inputs in primary somatosensory cortex. Bodily illusions (RHI, full-body illusions modulated by synchrony with heartbeats or breathing) are read as this integration building the bodily self (Fig. 4f). Connects to experience-of-body-ownership and multisensory-integration.
Where this sits in the wiki
This review is the rhythm-based counterpart to the perception-based tradition that dominates the wiki. It does not touch the heartbeat-counting validity debate (is-the-heartbeat-counting-task-valid) because it does not use perceptual report as its measure; it sidesteps the cross-modal decorrelation problem (Banellis et al.) because it is not measuring an individual’s accuracy on each channel but the coupling of each channel to cortex — though the reliability worry from Levakov et al. and is-brain-body-coupling-a-reliable-individual-difference applies with full force to any individual-differences use of these coupling measures, which the review does not pursue.
Its most useful gift to the wiki is the cardiac-cycle-effects construct, absent until this ingest and already touched by García-Cordero and Schulz. Its most quotable line is the closing one: taking interoception and exteroception in the same framework “paves the way for biological modes of information processing specific to living organisms” — the claim that a brain in a body computes differently from a brain in silico, and that the body’s rhythms are part of the reason.