Complex auditory brainstem response in normal-hearing adults using binaural versus monaural speech stimuli

Abstract

BackgroundBinaural hearing refers to the ability of the auditory system to integrate sounds reaching both ears. The complex auditory brainstem response (cABR) to the /da/ synthetic syllable gives information about time-locked response that is either transient or sustained depending on the periodic or nonperiodic characteristics of the stimulus.ObjectiveThis is a preliminary research that was performed to study the binaural interaction component of cABR in normal-hearing adults.Patients and methodsThis study included 20 normal-hearing adults, whose age ranged from 15 to 60 years, with a mean age of 29.30±12.52 years. CABR was conducted for all patients. The stimulus used was the syllable [da] (40 ms), presented first monaurally (left and right) and then binaurally through TDH headphones, in alternating polarity at 80 dBnHL. The binaural interaction component (BIC) was then computed by subtracting the binaural waveform from the sum of the two monaural responses.ResultsThe mean right amplitudes were smaller than binaural amplitudes for waves V, A, C, D, E, and F. However, this difference was statistically significant at D, E, and F waves only. The mean left amplitudes were smaller than binaural amplitudes for waves V, A, C, D, and E only. In addition, this difference was statistically significant. The mean binaural amplitudes were smaller than the summed right+left amplitudes for waves V, A, C, D, E, F, and O. There was no statistically significant difference among the mean latencies of responses recorded from right, left, or binaural for all cABR waves.ConclusionBICs reflecting binaural process can be obtained for ABR using speech stimuli comparing the binaural and summed monaural recorded responses. We recommend assessing the BIC on a large scale to obtain normative data, for comparison with patients with known auditory processing capabilities (shown by behavioural tests) to see how well the data can be used as an index of binaural process.