Electroencephalographic responses to briefly introduced interaural intensity differences

The stimulation techniques so far described in the literature, for recording the long-latency electroencephalographic responses to changes in interaural intensity difference (IID), cannot be regarded as being specific for binaural mechanisms because any change in IID has inevitably a stimulating effect also on purely monaural mechanisms. However, by making use of the relatively long recovery characteristics of cortical responses we were able to design a novel IID-stimulus, which did not evoke any significant potential when it was presented monotically or diotically, yet produced lateral sound image shifts and therefore evoked pronounced long-latency responses when presented dichotically. The shift responses recorded from five subjects mainly consisted of a negative-positive wave sequence at latencies around 110 ms and 200 ms, respectively. These vertex potentials, which were tested in this work receive no significant contribution from the monaural or binaural mechanisms sensitive to overall sound intensity, should be useful as a diagnostic tool for assessing the level of maturation or the integrity of the sound lateralization mechanism based on IIDs.