Dijk D J
Circadian, Neuroendocrine and Sleep Disorders Section, Division of Endocrinology, Department of Medicine, Harvard Medical School & Brigham and Women's Hospital, Boston, MA 02115, USA.
J Sleep Res. 1999 Sep;8(3):189-95. doi: 10.1046/j.1365-2869.1999.00159.x.
In humans, EEG power spectra in REM and NREM sleep, as well as characteristics of sleep spindles such as their duration, amplitude, frequency and incidence, vary with circadian phase. Recently it has been hypothesized that circadian variations in EEG spectra in humans are caused by variations in brain or body temperature and may not represent phenomena relevant to sleep regulatory processes. To test this directly, a further analysis of EEG power spectra - collected in a forced desynchrony protocol in which sleep episodes were scheduled to a 28-h period while the rhythms of body temperature and plasma melatonin were oscillating at their near 24-h period - was carried out. EEG power spectra were computed for NREM and REM sleep occurring between 90-120 and 270-300 degrees of the circadian melatonin rhythm, i.e. just after the clearance of melatonin from plasma in the 'morning' and just after the 'evening' increase in melatonin secretion. Average body temperatures during scheduled sleep at these two circadian phases were identical (36.72 degrees C). Despite identical body temperatures, the power spectra in NREM sleep were very different at these two circadian phases. EEG activity in the low frequency spindle range was significantly and markedly enhanced after the evening increase in plasma melatonin as compared to the morning phase. For REM sleep, significant differences in power spectra during these two circadian phases, in particular in the alpha range, were also observed. The results confirm that EEG power spectra in NREM and REM sleep vary with circadian phase, suggesting that the direct contribution of temperature to the circadian variation in EEG power spectra is absent or only minor, and are at variance with the hypothesis that circadian variations in EEG power spectra are caused by variations in temperature.
在人类中，快速眼动（REM）睡眠和非快速眼动（NREM）睡眠中的脑电图功率谱，以及睡眠纺锤波的特征，如持续时间、振幅、频率和发生率，都随昼夜节律阶段而变化。最近有人提出假设，人类脑电图谱的昼夜节律变化是由大脑或体温的变化引起的，可能并不代表与睡眠调节过程相关的现象。为了直接验证这一点，我们对脑电图功率谱进行了进一步分析，这些数据是在强迫去同步化方案中收集的，在该方案中，睡眠时段被安排为28小时，而体温和血浆褪黑素的节律则以接近24小时的周期振荡。计算了在昼夜褪黑素节律90 - 120度和270 - 300度之间出现的NREM和REM睡眠的脑电图功率谱，即分别在“早晨”血浆褪黑素清除后和“傍晚”褪黑素分泌增加后。在这两个昼夜节律阶段的预定睡眠期间，平均体温相同（36.72摄氏度）。尽管体温相同，但在这两个昼夜节律阶段，NREM睡眠中的功率谱却非常不同。与早晨阶段相比，傍晚血浆褪黑素增加后，低频纺锤波范围内的脑电图活动显著增强。对于REM睡眠，在这两个昼夜节律阶段的功率谱也存在显著差异，特别是在α频段。结果证实，NREM和REM睡眠中的脑电图功率谱随昼夜节律阶段而变化，这表明温度对脑电图功率谱昼夜节律变化的直接贡献不存在或很小，这与脑电图功率谱的昼夜节律变化是由温度变化引起的假设不一致。
