It is known that autonomic nervous activities change in correspondence with sleep stages. However, the characteristics of continuous fluctuations in nocturnal autonomic nerve tone have not been clarified in detail. The study aimed to determine the possible correlation between the electroencephalogram (EEG) and autonomic nervous activities, and to clarify in detail the nocturnal fluctuations in autonomic nerve activities. Overnight EEGs and electrocardiograms of seven healthy males were obtained. These EEGs were analyzed by fast Fourier transformation algorithm to extract delta, sigma and beta power. Heart rate and heart rate variability (HRV) were calculated in consecutive 5-min epochs. The HRV indices of low frequency (LF), high frequency (HF) and LF/HF ratio were calculated from the spectral analysis of R-R intervals. The sleep stages were manually scored according to Rechtschaffen and Kales' criteria. Low frequency and LF/HF were significantly lower during non-rapid eye movement (NREM) than REM, and were lower in stages 3 and 4 than in stages 1 and 2. Furthermore, delta EEG showed inverse correlations with LF ( r = -0.44, P < 0.001) and LF/HF ( r = -0.41, P < 0.001). In contrast, HF differed neither between REM and NREM nor among NREM sleep stages. Detailed analysis revealed that correlation was evident from the first to third NREM, but not in the fourth and fifth NREM. Delta EEG power showed negative correlations with LF and LF/HF, suggesting that sympathetic nervous activities continuously fluctuate in accordance with sleep deepening and lightening.

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We studied changes in the sleep patterns of ten young women from late pregnancy (36 weeks) to the sixth postpartum week, focusing on the relationship between the women's sleep patterns and their infants' movements. The mothers' polysomnograms and their infants' ankle actigrams were simultaneously recorded using a Medilog 9000 at home in three sessions, during the first, third, and sixth postpartum weeks. The mother-infant pairs slept in close proximity. Two subjects had difficulty with their infants and were dealt with as a separate group. Analysis for the eight subjects who adapted well to the postpartum period showed that wake time after sleep onset increased significantly during the postpartum period compared with late pregnancy given responsibility for feeding. Stage 3 + 4 and Stage REM did not change across the four sessions (pregnancy, first, third, and sixth postpartum weeks), but Stage 2 decreased significantly from pregnancy to postpartum. There was a high synchronization between infants' movements and mothers' wakefulness. Eight mothers did not complain of sleep disturbance, while the two mothers who had difficulty with their infants did. We suggest that mothers who tolerate well sleep interruption arising from feeding and maintain their Stages 3 + 4 and REM should not be considered as suffering from sleep disturbance. Mothers who have difficulty with their infants and complain of sleep disturbance should be considered as suffering from sleep disturbance.

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SUMMAR Y To investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole-night polysomnograms of narcoleptic patients and normal human subjects. Eight drug-naive narcoleptic patients and eight age-matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)-density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non-rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0-1.4 Hz and 11.0-11.9 Hz frequency bands, and decreased in a 24.0-26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.k e y w o r d s narcolepsy, pathophysiology, power spectral analysis, rapid eye movement density, rapid eye movement sleep