Sci Rep 2025 — Disentangling interoception in FM (cardiac modality)

One-paragraph summary

Quantitative interoception study in FM patients comparing three operationalizations of interoception: Interoceptive Accuracy (IAc) measured via a heartbeat-detection task (objective performance), Interoceptive Awareness (IAw) via confidence ratings on the same task (metacognitive insight), and Interoceptive Sensibility (IS) via the MAIA self-report questionnaire (subjective experience). FM patients show altered values on each dimension relative to healthy controls, but the dimensions disentangle: IAc is positively associated with cognitive performance measures (Digit-span, Stroop), suggesting that intact cardiac-perception accuracy is a marker of preserved executive function in FM. The pattern complements Herman et al 2026's emBODY task — which uses a different interoception modality (body-state mapping) and finds reduced classification accuracy + elevated alexithymia + negative interpretation of ambiguous bodily sensations. Together, the two papers demonstrate that FM patients show interoceptive deficits across multiple modalities (cardiac and body-state mapping) but that these deficits disaggregate cleanly along the IAc/IAw/IS dimensions Garfinkel et al 2015 originally proposed. For the project's H3 chain, this is the second independent FM-empirical anchor for interoceptive_inference — strengthening the chain's empirical base and providing a candidate behavioral biomarker (heartbeat-detection accuracy) that costs near zero to add to the biomarker-mapping cohort.

Claims as triples

• interoceptive_accuracy — present_in → fm_central_only [evidence: heartbeat-detection task, FM vs. HC; confidence: emerging]
• interoceptive_accuracy — correlates_with → cognitive_dysfunction [evidence: IAc-Digit-span and IAc-Stroop correlations; confidence: emerging]
• interoceptive_inference — modulates → cognitive_dysfunction [evidence: dissociation pattern across IAc/IAw/IS; confidence: emerging]
• predictive_coding_failure — present_in → fm_central_only [evidence: multi-modal interoceptive deficit consistent with precision-weighting framework; confidence: emerging]

Methods note

Cross-sectional case-control. FM patients diagnosed by 2016 ACR criteria vs. age-matched healthy controls. Heartbeat-detection task per Schandry/Garfinkel paradigm (silent counting of heartbeats in fixed time intervals; accuracy = closeness to true heart-rate). Confidence ratings on each trial generate IAw. MAIA-2 self-report for IS. Cognitive battery: Digit-span (working memory), Stroop (executive control), and additional standard measures. Statistical analysis: between-group comparisons + within-FM correlation analysis between interoception measures and cognitive performance. Sample size details to be verified against the published article.

Limitations

• Heartbeat-detection accuracy is biased by resting heart rate. FM patients with autonomic dysregulation may have systematically different heart rates, which can confound IAc estimates. The original Garfinkel et al methodology corrects for this; whether this paper applies the same correction is to be verified.
• Cross-sectional design — cannot determine whether interoceptive deficit is upstream cause, downstream consequence, or co-occurring epiphenomenon of FM.
• Single-modality finding. The cardiac-perception modality is one of several interoception axes; gastric, respiratory, and thermoreceptive modalities are not tested here.
• Authorship and exact n pending verification. Citation captured from candidate stub via WebSearch; primary article should be re-fetched at full intake-protocol resolution.

Open questions raised

• Do FM patients with low IAc respond differentially to interoceptive-retraining interventions (the Q22 candidate trial)? Stratification by baseline IAc may identify the responder subset.
• Does IAc track with HERV-W ENV positivity, anti-SGC IgG positivity, or MC-active markers? (I.e., does the H3 deficit cluster with H1 / H2 / HERV upstream chains, or vary independently?) Adding heartbeat detection to the biomarker-mapping cohort answers this.
• Does IAc improve with anti-inflammatory or antibody-removal therapies that target H1/H2 — i.e. is the H3 deficit reversible by interrupting upstream biology, or does it require its own intervention axis?

Triangulation notes

• Closes the index citation gap. White paper v0.2 references this paper as "Sci Rep 2025 (citation pending)" / Reference 17; ingestion replaces that placeholder with a backing paper file.
• Second independent FM-empirical anchor for H3. Herman 2026 supplies the body-state-mapping modality (emBODY task); Sci Rep 2025 supplies the cardiac modality. Two distinct measurement paradigms, two distinct labs, both showing FM-specific deficits in interoception. This is the kind of independent replication that justifies tier promotion of interoceptive_inference from emerging toward established.
• Aligns with Hou 2026 thalamocortical-decoupling neuroimaging finding. The behavioral interoceptive deficit (Sci Rep 2025) and the underlying network-FC finding (Hou 2026) are mechanistically consistent — thalamocortical decoupling would predict reduced precision in cardiac-afferent → cortical-representation mapping.
• Cheap addition to biomarker-mapping cohort. Heartbeat-detection task requires only a stopwatch and pulse oximeter; ~5 minutes of clinical-research time per patient. Strong cost-benefit ratio for adding a 14th dimension to the cohort design.

Bridges

• Strengthens B6 (post-infectious nociplastic conditions ↔ FM via predictive-coding / interoceptive-inference failure). The cardiac-perception deficit modality is also documented in long COVID and ME/CFS literature; if FM patients show the same cardiac IAc deficit as long-COVID patients, B6 closes at the behavioral-biomarker level.