The Vagal Wire: The Bidirectional Anatomy of the Brain-Body Threat Loop

This is the authors' abstract. We don't add key points for this paper.

The companion papers describe a self-referential loop: the brain issues a defensive decree, the decree damages peripheral organs, the damaged organs signal distress back to the brain, and the brain tightens the decree. This paper proposes that the vagus nerve is the physical substrate of that loop.The anatomy is established for the heart, lungs, liver, gut, and kidney: the vagus innervates these organs, approximately 80% of its fibres are afferent, and its efferent arm carries the cholinergic anti-inflammatory signal. The eye is not vagally innervated, but trigeminal afferents from the eye converge with vagal afferents at the nucleus tractus solitarius. Vagal involvement in the bone marrow, prostate, and ovary is documented or proposed but is less firmly established, and should be described as a hypothesis rather than settled anatomy. What is not established is the framework interpretation—that vagal tone is the measurable substrate of the self-referential loop, that UBTI tracks vagal tone, that Tier 1 agents work in part by restoring it, and that the shared circuit explains why treating one disease raises another. This paper states that interpretation as a set of falsifiable predictions. If the predictions fail, the interpretation is wrong. No claim is made beyond what the predictions can test. Keywords: vagus nerve; cholinergic anti-inflammatory pathway; interoception; nucleus tractus solitarius; trigeminal-vagal convergence; UBTI; hypoxic cascade; Stasis-Acidosis-Proteinopathy; HRV; organ-specific inflammation; tilted equilibrium; ovarian cysts; unprotected sentinel; doorkeeper; falsifiable predictions