Homo- and anti-phasic stimulation in ABR.

Effects of homo-phasic and anti-phasic stimulation on the binaurally evoked auditory brain-stem responses (ABRs) were investigated in 10 normal subjects. Clicks were presented at 47 dB SL with two in-phase (binaural condensation and binaural rarefaction) and two out-of-phase (left ear condensation, right ear rarefaction and right ear condensation, left ear rarefaction) stimulus configurations. The earlier of the latencies obtained with homo-phasic stimulation were compared with the earlier of the latencies obtained with anti-phasic stimulation. Repeated measures ANOVAs on the peaks (P) and troughs (N) of each component, revealed significantly earlier latencies for the anti-phasic condition, for components II N (p less than 0.049), III P (p less than 0.012) and VIN (p less than 0.025). Similar trends were apparent for components IVP (p less than 0.075), VP (p less than 0.099) and VIP (p less than 0.12). The results are discussed in terms of the binaural-level difference phenomenon and possible clinical applications.