Cortical Informational Field Theory V: ADHD as a Near-Critical Cortical Regime (RC³) 3.

The Cortical Informational Field Theory (CIFT; Papers I–IV) establishes a mesoscopic field equation for cortical dynamics in which the excitation-inhibition balance parameter λCIFT, the effective diffusion coefficient Dₑff, and the admittance field χ (x, t) jointly determine the coherence length ξ, the structural capacity Nₑff, and the accessible richness R of conscious cortical states. The present work applies this framework to attention-deficit/hyperactivity disorder (ADHD), proposing that ADHD corresponds to a near-critical cortical regime (RC³) in which λCIFT fluctuates chronically near the critical threshold λc. Within this view, ADHD is interpreted not primarily as cortical disorganization, but as a dynamically distinct architecture whose adaptive or maladaptive expression depends on environmental context. The framework is further motivated by evolutionary considerations and by genomic evidence suggesting long-term persistence of attention-related variants across human history. Empirical grounding comes from task-based fMRI analysis (ds002424, OpenNeuro; n = 27), showing increased inter-task cortical reconfiguration in ADHD across language-processing task pairs (R = 1 - r; Cohen’s d = 0. 73-0. 79), consistent with the near-critical field prediction R ∝ 1/ΔU = 4β/λₑff². The pharmacological account formalizes methylphenidate as a χ (x, t) modulator and amphetamine as a direct λCIFT elevator. Eight falsifiable predictions are derived algebraically from the field equation. The paper concludes by proposing RC³ as a nomenclature consistent with the dynamical, empirical, and evolutionary structure of the model.