[Influence of interaural time- and level differences on the binaural interaction components in normal adults]

Binaural interaction components of auditory brainstem responses have long been studied and its beta-wave has been shown to be correlated with directional hearing ability. As patients with auditory processing disorders such as patients with some sorts of learning disabilities frequently have difficulties with binaural processing it seems sensible to use binaural interaction components in the diagnosis of these disorders.

In order to obtain normal values and to investigate the influence of interaural time (ITD) and level differences (ILD) binaural interaction components were measured in 21 adults. Interaural time differences varied between 0 and 1.2 ms and interaural level differences between 0 and 30 dB.

beta-latencies increased significantly as interaural time differences increased while beta-amplitudes did not change significantly. In measurements with higher interaural time differences detection of the beta-wave was only rarely possible. The effect of interaural level differences on beta-latencies was less pronounced and not significant as well as the influence of interaural level differences on beta-amplitudes.

In the present study it could be shown that the beta-wave of the binaural interaction waveform is present in almost every normal hearing subject. As amplitudes show a considerable variation beta-latencies seem to be of higher diagnostic value than amplitudes.