Frequency-Specific Operant Learning in Neurofeedback Reveals Distinct Cortical Mechanisms: Evidence from Double-Blind ERSP and ERP Dissociations

BackgroundNeurofeedback reliably alters EEG activity, but the cortical mechanism by which reward-contingent feedback shapes oscillatory dynamics remains unresolved. In particular, no study has examined reward-locked event-related spectral perturbations (ERSP) under double-blind, active-placebo-controlled conditions. MethodsForty participants underwent five training sessions and a 3-5 week retention session of single-channel EEG biofeedback (C3 SMR 12-15 Hz, n = 8; C3 Beta 15-18 Hz, n = 8; C4 SMR 12-15 Hz, n = 8; active-placebo sham, n = 16), with concurrent 64-channel EEG recording. ERSP was computed from reward-locked epochs (approximately 600-700 trials per session) using Morlet wavelets (3-40 Hz) across four sessions. ResultsActive groups produced frequency-specific event-related desynchronization (ERD) in the rewarded band (pooled Active vs Sham d = -1.23, padj = 0.001; C3 Beta and C4 SMR FDR-significant, |d| [≥] 1.12; C3 SMR trended, d = -0.80, padj = 0.081), absent in sham. A double dissociation emerged at C3: beta training produced the strongest ERD (d = -2.38), whereas C3 SMR training produced the largest P2 suppression (d = -1.33, BF01 = 0.10; smaller P2 at the trained electrode). Only SMR groups showed lasting plasticity, with increased eyes-closed alpha at follow-up (C3 SMR d = 0.97; C4 SMR d = 0.78) and significant across-session accumulation ({beta} = 1.44, p = 0.004). ERD magnitude predicted long-term resting-state change (r = 0.54, p = 0.009) but not within-session shifts (r = -0.09, p = 0.67), dissociating transient from consolidating effects. An ICA-based sensitivity analysis confirmed convergence of all primary findings. ConclusionsNeurofeedback engages frequency-specific, contingency-dependent cortical mechanisms. The ERD-P2 dissociation suggests that beta and SMR training recruit distinct circuits (C3 Beta: local cortical ERD with preserved P2; C3 SMR: putative thalamocortical relay ERD with suppressed P2 at the trained site) with different capacities for consolidation. These findings establish a multi-timescale model in which immediate reward-locked desynchronization drives durable plasticity only when supported by deeper circuit dynamics.