Masuda Kosaku, Katsuda Yoko, Niwa Yasutaka, Sakurai Takeshi, Hirano Arisa
Institute of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki, Japan.
Front Neurosci. 2023 May 12;17:1173537. doi: 10.3389/fnins.2023.1173537. eCollection 2023.
Aging disrupts circadian clocks, as evidenced by a reduction in the amplitude of circadian rhythms. Because the circadian clock strongly influences sleep-wake behavior in mammals, age-related alterations in sleep-wake patterns may be attributable, at least partly, to functional changes in the circadian clock. However, the effect of aging on the circadian characteristics of sleep architecture has not been well assessed, as circadian behaviors are usually evaluated through long-term behavioral recording with wheel-running or infrared sensors. In this study, we examined age-related changes in circadian sleep-wake behavior using circadian components extracted from electroencephalography (EEG) and electromyography (EMG) data. EEG and EMG were recorded from 12 to 17-week-old and 78 to 83-week-old mice for 3 days under light/dark and constant dark conditions. We analyzed time-dependent changes in the duration of sleep. Rapid eye movement (REM) and non-REM (NREM) sleep significantly increased during the night phase in old mice, whereas no significant change was observed during the light phase. The circadian components were then extracted from the EEG data for each sleep-wake stage, revealing that the circadian rhythm in the power of delta waves during NREM sleep was attenuated and delayed in old mice. Furthermore, we used machine learning to evaluate the phase of the circadian rhythm, with EEG data serving as the input and the phase of the sleep-wake rhythm (environmental time) as the output. The results indicated that the output time for the old mice data tended to be delayed, specifically at night. These results indicate that the aging process significantly impacts the circadian rhythm in the EEG power spectrum despite the circadian rhythm in the amounts of sleep and wake attenuated but still remaining in old mice. Moreover, EEG/EMG analysis is useful not only for evaluating sleep-wake stages but also for circadian rhythms in the brain.
衰老会扰乱生物钟，昼夜节律振幅的降低就是明证。由于生物钟对哺乳动物的睡眠-觉醒行为有强烈影响，与年龄相关的睡眠-觉醒模式改变可能至少部分归因于生物钟的功能变化。然而，衰老对睡眠结构昼夜特征的影响尚未得到充分评估，因为昼夜行为通常是通过使用转轮或红外传感器进行长期行为记录来评估的。在本研究中，我们使用从脑电图（EEG）和肌电图（EMG）数据中提取的昼夜节律成分，研究了与年龄相关的昼夜睡眠-觉醒行为变化。在光照/黑暗和持续黑暗条件下，对12至17周龄和78至83周龄的小鼠进行了3天的EEG和EMG记录。我们分析了睡眠时长随时间的变化。老年小鼠夜间快速眼动（REM）睡眠和非快速眼动（NREM）睡眠显著增加，而在光照阶段未观察到显著变化。然后从每个睡眠-觉醒阶段的EEG数据中提取昼夜节律成分，结果显示老年小鼠NREM睡眠期间δ波功率的昼夜节律减弱并延迟。此外，我们使用机器学习来评估昼夜节律的相位，将EEG数据作为输入，睡眠-觉醒节律的相位（环境时间）作为输出。结果表明，老年小鼠数据的输出时间往往延迟，特别是在夜间。这些结果表明，尽管老年小鼠的睡眠和觉醒量的昼夜节律减弱但仍然存在，衰老过程仍会显著影响EEG功率谱中的昼夜节律。此外，EEG/EMG分析不仅有助于评估睡眠-觉醒阶段，还有助于评估大脑中的昼夜节律。
