Contribution of auditory evoked potentials to binaural processing

Abstract

The contribution of the early (ABR), middle (MLR), and late (LLR) auditory evoked potentials (AEPs) to binaural interaction (BI) was studied in 17 normal young adults. AEPs were recorded by an electrode at C2 and referenced to a noncephalic electrode at CVII. Filtering was between 10 and 3000 Hz for both the ABR and MLR, and between 1 and 500 Hz for the LLR. Rarefaction clicks with an intensity of 60 dB above threshold for wave V of the ABR were presented at 11.1/s for both the ABR and MLR, and at 1.7/s for the LLR. Two samples of 2000 trials each were averaged for right monaural, left monaural, and binaural stimulus presentation. The binaural interaction component (BIC) was obtained by subtracting the sum of the monaural responses from the binaural response. Maximum BI in the ABR occurred at 7.35 ms with a mean BIC of 23%. Maximum BI occurred in the MLR at 39.6 ms with a mean BI of 49%. Maximum BI of the LLR occurred at 145 ms with a mean BI of 46%. This would indicate that BI is primarily medicated at the time of the generation of the N40 component of the MLR and that binaural processes constitute a major function of the auditory pathway rostral to the pons. [Work supported by NIH Grant ♯NS-11876.]