Binaural Summation of Surface-Recorded Electrocochleographic ResponsesNormal-hearing Subjects

Abstract

Surface-recorded electrocochleographic responses to monaural and binaural clicks were examined in 14 normal-hearing adults at 6 different sensation levels (90, 70, 50, 30, 20 and 10 dB). The amplitudes were measured as the peak-to-peak magnitude of the Jewett₅-FFP₇ complex. Across subjects and across the 5 first-mentioned sensation levels, binaural stimulation was found to increase the response amplitude by more than 60%. At 10 dB sensation level, responses were generally present, usually seen most clearly in tracings obtained with bilateral stimulation, but not sufficiently reproducible to warrant measurement of the amplitude. On average, binaural stimulation with moderate intensity (50 dB) clicks yielded responsens of almost the same amplitude as responses to high intensity (90 dB) monaural stimuli. This binaural summation effect exceeds the binaural summation effect for slow auditory potentials by far. It greatly facilitates registration of the brain stem evoked potentials and in clinical work with infants the binaural mode of presentation is likely to prove advantageous.