Effect of sleep on binaural interaction in human auditory evoked potentials

Binaural interaction (BI) in ABR, MLR and two kinds of 40-Hz steady-state responses (SSRs) were measured in the waking and sleeping states in normal adults. Eleven samples each were collected from 20 subjects. The ABR and MLR were elicited with 500-Hz tone pips. The SSRs were elicited with the same tone pips (pipSSR) or sinusoidally amplitude-modulated tones of the same frequency (samSSR). The amplitude differences between the summed monaural and binaural responses relative to the summed monaural responses were referred to as BI. ANOVA showed that the mean BI in the responses tested was significantly lower (p < 0.005) in the sleeping state than in the waking state. Ad hoc analysis revealed that the significant difference (p < 0.05) in BI between the waking and sleeping states occurred in the pipSSR and samSSR. The BI became larger in the order, ABR, samSSR, pipSSR, MLR, in both the waking and sleeping states. Significant differences (p < 0.05) were detected in the BI during sleep between the MLR and each of the other three responses, whereas in the waking state no significant difference was found between the MLR and tone-pip SSR.