Altered Neural Oscillations and Hemispheric Asymmetry in Single-Sided Deafness

Single-sided deafness (SSD) disrupts binaural auditory input and can lead to cortical reorganization affecting neural oscillatory activity. Whether the side of hearing loss (left versus right) yields distinct electroencephalography (EEG) spectral and lateralization patterns remains unclear. We compared spectral resting-state EEG power and hemispheric asymmetry among patients with left SSD (LSSD), right SSD (RSSD), and normal-hearing controls (NH).

Resting-state EEG was recorded from 100 participants, including 32 with LSSD, 31 with RSSD, and 37 NH. A power spectrum was computed for six canonical frequency bands (δ, θ, α, β, γ1, γ2). Group differences in spectral power were tested, and hemispheric asymmetry was quantified with a lateralization index per band. Associations between EEG measures and hearing thresholds, the Speech, Spatial and Qualities of Hearing Scale, and speech recognition were analyzed.

Compared with NH, both LSSD and RSSD showed a significant increase in γ1 power over frontocentral to posterior regions. Notably, RSSD additionally exhibited widespread power increases in the θ and β bands, with pronounced effects in frontocentral and parieto-occipital regions. Lateralization analysis revealed stronger right-hemisphere dominance in the parietal δ and θ power in RSSD compared with NH, whereas LSSD showed a large symmetric power distribution and did not differ significantly from NH. No significant associations were observed between spectral power and clinical measures after multiple-comparison correction.

Resting-state EEG indicates side-specific cortical reorganization in SSD. LSSD is marked by localized γ1 band enhancements, whereas RSSD shows more widespread power increases and greater right-hemispheric dominance in low frequencies. These asymmetric patterns suggest distinct compensatory mechanisms involving attention and multimodal integration and may have implications for laterality-specific rehabilitation approaches.