Associations Between Resting-State EEG Delta-band Activity at Selected Parietal Electrodes and Cognitive Changes Following Transcutaneous Auricular Vagus Nerve Stimulation in Patients with Mild Cognitive Impairment: An Exploratory Analysis

INTRODUCTION: Transcutaneous auricular Vagus Nerve Stimulation (taVNS) may improve cognition in Mild Cognitive Impairment (MCI), but its electrophysiological correlates remain unclear. We explored whether parietal delta-band changes were associated with cognitive changes following taVNS. METHODS: This exploratory secondary analysis included 26 participants with MCI from a randomized, double-blind, sham-controlled trial (taVNS, n = 14; sham, n = 12) who had valid resting-state EEG data at baseline and Week 24. Absolute and relative 1-3 Hz delta power at Pz, P1, P2, and P5 were analyzed using repeated-measures ANOVA and EEG-cognitive correlations with Benjamini-Hochberg FDR correction. RESULTS: Absolute delta power showed significant time effects at all four electrodes after FDR correction (all q = 0.008). Relative delta power at Pz showed an uncorrected group effect (F = 5.007, p = 0.035; q = 0.218). In the taVNS group, MoCA-B improvement was positively associated with relative delta-power changes at P1, P2, and P5 (r = 0.629-0.652, p = 0.012-0.016), whereas AVLTN7 improvement was negatively associated with absolute delta-power changes across Pz, P1, P2, and P5 (coefficients = -0.418 to -0.613, p = 0.020-0.048). Although these correlations did not reach statistical significance after correction for multiple comparisons, they showed a relatively consistent direction across multiple electrodes. DISCUSSION: Relative and absolute delta power may reflect complementary aspects of spectral modulation. The convergent cross-electrode associations provide preliminary EEG evidence linked to cognitive response to taVNS. CONCLUSION: Parietal delta-band power may represent a candidate electrophysiological marker of cognitive change following taVNS in MCI. These exploratory findings support further validation of predefined EEG biomarkers in larger, prospectively powered studies. CLINICAL TRIAL REGISTRATION: http://www.chictr.org.cn (ID: ChiCTR2000038868).