Impact of tinnitus on chirp-evoked auditory brainstem response recorded using maximum length sequences

Tinnitus is considered a potential consequence of cochlear synaptopathy. While animal studies have shown that this neural deafferentation reduces wave I amplitudes of the auditory brainstem response (ABR) at suprathreshold levels, studies in humans with tinnitus have reported conflicting results. To enhance the sensitivity of ABRs in detecting neurophysiological conditions associated with tinnitus, this study aimed to examine chirp-evoked ABRs in normal-hearing individuals with tinnitus using the maximum length sequence (MLS) technique. Chirp stimuli improve synchronous neural discharge during ABR recording, while the MLS technique enables the extraction of evoked responses from overlapping waveforms. We hypothesized that this combined approach would more effectively reveal ABR morphological characteristics associated with tinnitus. The results indicated no significant difference in noise exposure between the tinnitus and control groups. However, the tinnitus group exhibited significantly larger wave I amplitude, prolonged wave V latency, and extended interpeak interval in MLS responses to chirps at the lowest stimulus rate of 13.8/s. These findings identify unique characteristics of MLS responses to chirps in individuals with tinnitus. We interpret our findings in relation to the ongoing discussion about the neurophysiological mechanisms of tinnitus. Further studies should be conducted to investigate possible etiologies of tinnitus.