Effects of Stimulus Polarity on Binaural Interaction of Auditory Brainstem Response

Abstract

Background and Aim: Binaural perception is an important ability in human auditory system in noisy evironment.The human click-evoked binaural interaction component has been known as an index of binaural perception. The purpose of this investigation was to study the stimulus polarity effect on binaural interaction of auditory brainstem response (ABR). Materials and Methods: ABR’s were recorded monaurally and binaurally in 30 normal adults (12 men & 18 women) using different stimulus polarity. In order to determine binaural interaction component (BIC) from wave V, the binaural response was subtracted from the summed monaural waves (R+L) in each polarity. Repeated measures ANOVA was used to analyze latency & amplitude differences of BIC between the three stimulus polarities. Results: Condensation clicks produced BIC’s with longer latency compared to rarefaction clicks (p˂0.05). BIC’s amplitude increased by using condensation polarity compared to rarefaction & alternate polarities ( p˂0.001 & p˂0.01, respectively). Conclusion: Amplitude, latency & morphologic characteristics of BIC were dependent on click polarity. Latency differences have been accounted for by small latency shift of the components of monaurally or binaurally evoked potentials resulting from changes in click polarity. Recognition of BIC was easier using condensation polarity. Key words: Binaural Interaction, Auditory Brainstem Response, Stimulus polarity