Exploration of sleep spindles from surgically induced unilaterally deaf adult humans with and without tinnitus

• Spindles may offer an index of abnormal thalamic reticular nucleus activity. • Data from unilaterally deaf individuals with and without tinnitus were compared. • Tinnitus spindle density/amplitude trends were non-significant; replication needed. In the neural noise-cancellation mechanism, reduced auditory thalamic reticular nucleus (TRN) activity is thought to result in tinnitus. As a biomarker of TRN activity is sleep spindles, we performed an exploratory study to ask whether individuals with tinnitus would exhibit altered sleep spindles compared with controls. Unilaterally deaf adults with tinnitus (UD + T; n = 13), without tinnitus (UD-T; n = 8), and controls without tinnitus or UD (CO; n = 13) were recruited. 2-hour polysomnography nap data were obtained from 64-channels. Spindles were characterised in both frequency and time domains. We observed no statistically significant differences between our groups in any parameter. However, a dual trend towards lower spindle density (1.8 ± 2.1 spindles/min) and higher spindle amplitude (24.6 ± 9.1 µV) amongst the UD + T group was noted. A tentative interpretation of the dual trends is the possible altered auditory TRN function associated with tinnitus. Albeit not statistically significant, these exploratory data at least provide a valuable foundation for future studies to probe the effect further. This includes a higher sample size and longer overnight sleep data. This is the first study which investigated sleep spindles in UD patients with and without tinnitus.