Can Mismatch Negativity Be Used as an Indicator to Predict Central Auditory Deficits in Individuals with Normal Hearing?

<b>Background/Objectives</b>: In the early stage of presbycusis, patients experience reduced speech perception in noisy environments despite normal audiometry, normally known as hidden hearing loss. Diagnostic indicators like the reduced amplitude of ABR wave I, elevated extended high-frequency threshold (EHT), and decreased middle ear muscle reflex (MEMR) amplitude aim to identify biomarkers of peripheral auditory pathology but remain inconsistent. Mismatch negativity (MMN) is a cortical auditory evoked potential generated when the brain detects sound changes. This study aimed to assess MMN as a diagnostic tool for hidden hearing loss in adults. <b>Methods</b>: Seventy-three subjects with normal hearing underwent an extended pure-tone audiogram examination ranging from 0.125 to 16 kHz and a subsequent MMN assessment with two different paradigms: a speech (ba/da) and a tone (1/2 kHz) paradigm. The MMN's amplitude and latency were measured and analyzed. <b>Results</b>: The outcome shows a significant age-related effect on MMN amplitude in the speech condition (χ² = 13.0, <i>p</i> = 0.002). Specifically, the MMN amplitude in the 25-30-year-old group was significantly smaller than in the 20-25-year-old group (<i>p</i> = 0.0015, Cohen's d = 0.63). Additionally, no further effects of age were observed on the cortical potentials examined. Also, neither tone nor speech paradigms showed a significant influence of EHT on the amplitude or latency of either MMN or P300. <b>Conclusions</b>: The application of MMN as an electrophysiological tool to diagnose hidden hearing loss in normal hearing adults has limitations. However, in contrast to MMN responses to tonal stimuli, the present study reveals that MMN amplitude obtained with speech stimuli may indicate early signs of central auditory deficits.