Thalamocortical dysrhythmia-related sleep spindle desynchronization in patients with tinnitus

Patients with tinnitus commonly suffer from sleep problems, and the underlying neural mechanisms remain unclear. Previous studies have focused primarily on the correlation between patients' sleep structure and tinnitus, lacking exploration into the links between sleep problems and the underlying pathological mechanisms of tinnitus, such as thalamocortical dysrhythmia (TCD). Here, we present the first study on neural oscillatory patterns in patients with tinnitus during sleep spindles, a more precise subdivision of sleep that overlaps in neuropathological pathways with TCD. Sleep electroencephalogram (EEG) were recorded from 51 tinnitus participants and 51 healthy participants. During sleep spindles, patients with tinnitus exhibited a significant increase in 18-45 Hz and a stronger cross-frequency coupling, resembling the EEG abnormalities caused by TCD during wakefulness. With respect to spindle characteristics, tinnitus is linked to an increase in spindle quantity but a decrease in spindle root-mean-square and functional connectivity, suggesting that normal function of tinnitus spindles is impaired. Our findings indicated that neural oscillation dynamics related to TCD during sleep spindles serve as neural biomarkers for sleep disturbances in tinnitus participants. We demonstrate that the impact of the TCD pathological mechanism in tinnitus is not confined to the waking state but extends into the sleep stage as well, which advances our comprehension of the neural mechanisms underlying sleep-related problems in tinnitus.