A Dynamical Reinterpretation of Functional Neurological Disorders

Patients with Functional Neurological Disorders (FNDs) develop motor, sensory and autonomic symptoms that are real and often disabling. They remain difficult to account for within conventional neurological frameworks, because no structural lesion adequate to explain them is found. Historically, these conditions were interpreted either as psychogenic disorders or as instances of organic disease that had not yet been correctly identified. More recently, they have been reconsidered in relation to predictive-processing accounts of perception and action. None of these approaches, however, supply a formal dynamical framework for understanding how symptoms take shape and become self-maintaining. Our aim in this paper is to provide such a framework. We develop a multilevel control-theoretic model in which peripheral physiology x, cortical predictive states m and policy-level agency a interact under conditions of precision-weighted free-energy minimization. From a minimal variational formulation incorporating prediction error, energetic control costs and allostatic load, we derive a reduced four-variable system consisting of autonomic volatility (V ), precision imbalance (ΔΠ), control burden (B) and load (L). The Jacobian and the Routh-Hurwitz conditions for the model show how symptom-producing attractors arise when volatility, distorted precision weighting and compensatory control amplify one another across levels of the system. Functional symptoms aren’t fictitious nor are they a kind of residual category that’s abandoned when structural explanations fail. They reflect lawful and potentially stable modes of dysregulation in a nonlinear organismic system. The model also clarifies why interventions such as autonomic retraining, exposure-based recalibration, behavioral activation and physical repair have therapeutic leverage. They don’t target a single hidden cause. Rather, each perturbs the relevant control dynamics in a unique way. The broader implication of the model is that FNDs are disorders of regulation, not representation.