Auditory brainstem responses: masking related changes in wave VI

Auditory brainstem responses (ABRs) were recorded in a group of nine normally-hearing subjects. Wide-band clicks were delivered at 70, 80 and 90 dB SL, both with and without 50 dB SL of contralateral masking. The amplitude of wave VI was significantly reduced in the presence of masking for the 90 dB SL stimulus but there was no effect at the lower stimulus levels. A possible explanation for this is that the observed response, to a 90 dB SL stimulus without masking, is a summation of the ipsilateral wave VI and a wave V elicited from the contralateral ear. Supporting evidence is provided and the implications of this result are discussed.