４０Ｈｚ聴性定常反応における睡眠の影響 Effect of Sleep on 40-Hz Auditory Steady-state Responses.
刺激頻度40Hzの聴性定常反応 (auditory steady-state response, 以下, SSR) における睡眠の影響を知ろうとして, 聴力正常成人9名を被検者とし, 500Hz, 55dBnHLの短音を用い, 刺激間隔125msでABR-MLRを, 間隔25msでSSR (以下実測SSR) を記録した。 さらにABR-MLR波形から25ms間隔の重ね合わせによって合成SSRを作成し, 主としてその振幅について検討した。 睡眠時/覚醒時の平均振幅の比はABR (V波) 0.648, Pa0.578, Pb0.338, 合成SSR0.604, 実測SSR0.398で, 睡眠時SSRの振幅は覚醒時の平均約40%に縮小した。 実測SSR/合成SSRの平均振幅の比は, 覚醒時0.845, 睡眠時0.557で, この振幅比については覚醒時と睡眠時の間に有意差が認められた。 この結果から, SSRがABR-MLRの直線的重ね合わせ反応であるとの解釈は, 覚醒時においては可能であるが, 睡眠時においては考え難いと結論した。
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).<br>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.
- ＡＵＤＩＯＬＯＧＹ ＪＡＰＡＮ
ＡＵＤＩＯＬＯＧＹ ＪＡＰＡＮ 36(1), 28-34, 1993