Abstract
40-Hz auditory steady-state response (SSR), ABR and MLR were recorded in the waking and sleeping states in 9 adults with normal hearing. The responses were elicited with 500Hz tone pips at 55dBnHL given with intervals of 25ms and 125ms for recording SSR and ABR-MLR, respectively. Each averaged response was the composite of 2048 stimulus presentations. Since the stage 2 sleep was most frequently observed in the sleeping state, amplitude measurement of the averaged responses was exclusively made in the responses recorded during the stage 2 sleep. Synthesized SSRs (sSSR) were made from the recorded ABR-MLR waveforms and their amplitudes were compared with those of the really recorded SSRs (rSSR).
In the waking state, the ratio of mean amplitudes of rSSR to sSSR reached 0.845:1, whereas the ratio decreased to 0.557:1 during sleep. Statistically significant difference was found in the values of ratios between awake and asleep states. The results supported the assumption that auditory SSR in the waking state was obtained from the linear super-imposition of ABR and MLR. However, such linear relationship between SSR and ABR-MLR could not be considered to exist in the sleeping state.
