ELECTROENCEPHALOGRAPHIC RESPONSES TO BRIEFLY INTRODUCED INTERAURAL INTENSITY DIFFERENCES

The stimulation techniques so far described in the literature, for rec ording the long-latency electroencephalographic responses to changes i n interaural intensity difference (IID), cannot be regarded as being s pecific for binaural mechanisms because any change in IID has inevitab ly a stimulating effect also on purely monaural mechanisms. However, b y making use of the relatively long recovery characteristics of cortic al responses we were able to design a novel IID-stimulus, which did no t evoke any significant potential when it was presented monotically or diotically, yet produced lateral sound image shifts and therefore evo ked pronounced long-latency responses when presented dichotically. The shift responses recorded from five subjects mainly consisted of a neg ative-positive wave sequence at latencies around 110 ms and 200 ms, re spectively. These vertex potentials, which were tested in this work re ceive no significant contribution from the monaural or binaural mechan isms sensitive to overall sound intensity, should be useful as a diagn ostic tool for assessing the level of maturation or the integrity of t he sound lateralization mechanism based on IIDs.