Onset-related differences in neural substrates of tinnitus-related distress: the anterior cingulate cortex in late-onset tinnitus, and the frontal cortex in early-onset tinnitus

Recent findings regarding differences in tinnitus-related neural activity according to onset age have raised a question on possible onset age-related differences in neural substrates of distress. Hence we collected quantitative electroencephalography (qEEG) findings of 28 late-onset tinnitus (LOT) and 29 early-onset tinnitus (EOT) (mean onset age 52.3 and 29.0 years, respectively) participants. According to the tinnitus questionnaire (TQ) score grade, LOTs were then subdivided into 13 high distress (HD; TQ grade 3 or 4) and 15 low distress (LD; TQ grade 1 or 2), while EOTs into 14 HD and 15 LD. Compared to the EOT group, the LOT group demonstrated increased qEEG source-localized activity and functional connectivity primarily in the anterior cingulate cortex (ACC) and parahippocampus. In subgroup comparisons, the ACC was activated more in HD-LOT participants than in LD-LOT participants for the beta 1, beta 2 and gamma frequency bands, while the left orbitofrontal cortex and left dorsolateral prefrontal cortex were activated more in HD-EOT than in LD-EOT for the delta/beta and gamma frequency bands, respectively. Even with the same amount of tinnitus-related distress level, responsible neural substrates are different according to the onset age. These differences may be important for exploring different target areas of treatment according to tinnitus onset age, as well as for conducting similar studies on other pathologies, such as depression or pain.