Origin of the click-evoked binaural interaction potential, beta, of humans

The human click-evoked binaural difference waveform has as its most prominent feature the peak, beta, which has been shown to be related to binaural perception. In normal human subjects, we investigated the effect upon beta of (1) delivering the clicks in the presence of high passed masking noise (4000 Hz cut-off) and (2) reversing click polarity. In the presence of the masker, little activity occurs at the time the click-evoked beta would be expected. No significant change in beta latency occurs when the click polarity is inverted. We conclude that beta is principally due to the high-frequency components of the broad band click, so that it is through the activity in high characteristic frequency auditory nerve fibers that click-evoked beta is generated. Because the medial superior olive is the major nucleus of the human superior olivary complex, our results suggest that beta is possibly generated by the high-frequency cells of the medial superior olive.