The Expanded Polyvagal Theory: A Systems-Based and Entropy-Oriented Interpretation of Autonomic Regulation

Autonomic regulation has traditionally been described using branch-based models that emphasize linear relationships between sympathetic and parasympathetic activity. While these approaches have contributed substantially to physiological research, they often struggle to account for the nonlinear, multiscale, and state-dependent organization observed in complex biological systems.This manuscript presents the Expanded Polyvagal Theory (TPE) as an interpretative and non-diagnostic theoretical model designed to integrate concepts from autonomic physiology, heart rate variability, complexity science, and entropy-oriented analysis. Rather than introducing new physiological mechanisms or reporting experimental findings, the framework reorganizes existing knowledge through a state-based perspective, emphasizing emergent patterns, metastability, and subsystem coupling across multiple temporal and organizational scales.Within this framework, General States are conceptualized as emergent configurations arising from coordinated interactions among autonomic subsystems, while Autonomic Subtypes are described as recurrent structural–functional motifs within these states. The enteric nervous system is explicitly incorporated as a structural component of autonomic organization, addressing a longstanding gap in conventional autonomic models. An interpretative protocol, OSIRIS, is introduced as a conceptual scaffold for the structured interpretation of multiscale heart rate variability patterns, without proposing diagnostic thresholds, predictive claims, or clinical decision-support functions.This manuscript is presented as a conceptual and hypothesis-generating preprint, intended to stimulate interdisciplinary discussion and theoretical refinement rather than to serve as a clinical or experimental report. By situating autonomic regulation within a complex systems and entropy-oriented framework, the Expanded Polyvagal Theory provides a coherent interpretative lens that may inform future empirical research, model development, and integrative approaches to autonomic physiology.