Neural signatures of altered adaptation to repetitive auditory stimulation in tinnitus

Abstract A growing body of studies has explored tinnitus within a predictive coding framework, proposing that predictive mechanisms may contribute to its development and persistence. However, many aspects of this relationship remain to be clarified. While mismatch negativity (MMN) has frequently been used to index prediction error or regularity violation, considerably less is known about neural responses that reflect the strengthening of predictions or stimulus adaptation; for instance, repetition positivity (RP), a gradual increase in positive ERP amplitude across repeated stimulus presentations, has been proposed to index the formation of sensory memory traces and the reinforcement of ongoing predictions, and the N1 potential is a fundamental auditory response to stimulus onset or change but which diminishes with stimulus repetition or regularity. In this study, we examined how auditory repetition shapes auditory RP and N1 responses in individuals with chronic tinnitus and mild tinnitus-related handicap ( N = 19), and age- and hearing-matched controls ( N = 18), using a highly repetitive isochronous roving frequency and intensity paradigm. RP and other evoked peaks did not differ significantly between groups, whilst N1 responses differed strikingly, being suppressed in the tinnitus group, present in the matched controls, and significantly different between the groups. Notably, the tinnitus group’s responses resembled a young normal-hearing group previously reported using the same paradigm. These findings suggest that tinnitus may be associated with altered auditory adaptation mechanisms operating across different timescales and processing stages, potentially reflecting stronger or more rapid auditory adaptation at early cortical processing stages, while later RP responses appear largely preserved.