Binaural interaction in human auditory brainstem evoked potentials.

Binaural interaction was examined by recording human auditory brainstem responses to clicks from scalp electrodes. Deviations of binaurally evoked responses from the sum of monaurally evoked potentials were observed during waves IV through VI. Amplitude and latency of the interactions depended on click polarity: condensation clicks produced interactions of larger magnitude and longer latency than did rarefaction clicks. Latency differences cannot be accounted for by small latency shifts of the components of monaurally or binaurally evoked potentials resulting from changes in click polarity. Binaural interaction amplitude decreased as click intensity decreased and interaural delay increased. Attenuation of binaural interaction with interaural time differences was maximal at an interaural delay of 900 microseconds. Latency of interaction was prolonged in one subject with low- and high-frequency hearing loss; latency of binaural interaction in subjects with only high-frequency hearing loss was normal. These results suggest that binaural interaction in these potentials reflects binaural processing of low-frequency acoustic stimulation.