Biomedical subjects

Kyoko Nishihara

Publications and source records attributed to Kyoko Nishihara.

6 recordsLinked to original sources

PubMed2004

Delta and theta power spectra of night sleep EEG are higher in breast-feeding mothers than in non-pregnant women.

The power spectra of night sleep EEGs of 12 breast-feeding 9-13 week postpartum mothers were analyzed and compared with those of 12 non-pregnant women. The power spectra in the delta and theta frequency range during NREM sleep for breast-feeding mothers were significantly higher than those for non-pregnant women. In addition, the all-night sleep patterns of the mothers were classified into two groups - interrupted sleep due to taking care of their infants and non-interrupted sleep - in order to observe the influence of partial sleep deprivation. The power spectra in the delta and theta frequency range were not significantly different between them. This result suggests that increased delta and theta power spectra during postpartum sleep do not result from partial sleep deprivation. The role of prolactin in breast-feeding mothers' sleep is also discussed.

Adult↗

PubMed2004

Clonidine effects on all-night human sleep: opposite action of low- and medium-dose clonidine on human NREM-REM sleep proportion.

Norepinephrine (NE) is considered to play a permissive role in the occurrence of rapid eye movement (REM) sleep. Clonidine is an NE alpha-2-receptor agonist, which has been considered to act mainly on the autoreceptors of presynaptic noradrenergic neurons to reduce their release of NE. However, previous studies of clonidine effects on REM sleep have produced controversial results and the effects of clonidine remain uncertain. To clarify the pharmacological effects of clonidine on human sleep, the sleep electroencephalograms (EEG) recorded from 15 young normal subjects after a single administration of either a low (25 micro g) or medium (150 micro g) dose of clonidine were examined, and fast Fourier transformation (FFT) spectral analyses of the C3-A2 EEG were performed. Low-dose clonidine significantly increased the amount of REM sleep and decreased the amount of non-REM (NREM) sleep during the second one-third of the drug nights compared to the corresponding hours of baseline night recordings. In contrast, medium-dose clonidine significantly decreased REM and increased NREM on drug nights compared to baseline nights in the entire night. The opposite actions of low and medium doses of clonidine on NREM-REM proportion may indicate that low-dose clonidine mainly affects the alpha-2-receptors on locus coeruleus-NE neurons presynaptically, reducing the release of NE, whereas medium-dose clonidine acts more post-synaptically.

Adrenergic alpha-2 Receptor Agonists↗

PubMed2003

Spectral analysis of all-night human sleep EEG in narcoleptic patients and normal subjects.

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.

Adult↗

PubMed2003

Correlation between electroencephalography and heart rate variability during sleep.

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.

Adult↗

PubMed2003

Long-, intermediate- and short-acting benzodiazepine effects on human sleep EEG spectra.

The effects of 10 mg haloxazolam (HAX), 4 mg flunitrazepam (FNZ), and 0.5 mg triazolam (TRI), each administered for seven consecutive nights were studied in the sleep electroencephalograms (EEG) of 17 (six HAX, five FNZ and six TRI) healthy male student volunteers. Recordings of C3-A1 EEG data from one baseline night, three drug nights (first, fourth and seventh) and two withdrawal nights (second and fourth) were analyzed using a fast Fourier transformation method. All three drugs induced similar changes in the 0.5 Hz to 40 Hz power spectrum; namely (i) higher frequency (including the sigma and beta bands) activity increased and lower frequency activity reduced on the drug nights; (ii) the enhancement of sigma activity peaked during non-rapid eye movement sleep following the first administration and was maintained at high levels on all drug nights; (iii) beta activity increased through the night after administration of HAX and FNZ, but not TRI, which suggests a blood concentration level dependent increase of beta activity; and (iv) only HAX showed a residual effect on the fourth withdrawal night. These results indicate that (i) chronic administration of these three benzodiazepine derivatives produce similar profiles in sleep EEG spectral changes, with some differences depending on their half-lives and doses; (ii) the mechanism of sigma enhancement is sensitive to even the initial administration night of BDZ; and (iii) frequencies below and above the sigma band are less sensitive to BDZ and also show an increase through the night after administration, suggesting differences in the mechanisms reflected by these EEG frequency bands.

Adult↗

PubMed2002

The development of infants' circadian rest-activity rhythm and mothers' rhythm.

In order to know when and how infants obtain their circadian sleep-wake rhythm, infants' developing circadian rest-activity rhythm and mothers' circadian rhythm in the postpartum period were examined using actigraph monitoring. The subjects were 11 primipara and their infants. Actigraphic recordings for the infants and their mothers were made over 3-5 continuous days during the 3rd, 6th, 9th and 12th weeks after birth. A 24-h peak on a mean autocorrelogram of the infants' movements was detected at the 3rd week. The infants' circadian rest-activity rhythm already existed in the 3rd week. The amplitude of this 24-h peak gradually increased from the 6th to 12th week. This may be useful as an index of the development of infants' circadian rest-activity rhythm. An 11-h peak was also observed at the 3rd week. This 11-h peak was thought to be a semi-circadian rhythm. Regarding the mothers, the amplitude of the 24-h peak on the mean autocorrelogram at the 3rd week was the smallest of all other weeks, and it became larger from the 3rd to 12th week. This meant that the mothers' circadian rhythm at the 3rd week was influenced by their interrupted sleep at night to take care of their infants. The mother-infant synchronization is probably the 1st factor in the entrainment of infants' circadian sleep-wake rhythm. In this study, we also propose a novel method for compensating for missing data in autocorrelogram analysis.

Activity Cycles↗