Linking stages of non-rapid eye movement sleep to the spectral EEG markers of the drives for sleep and wake

The conventional staging classification reduces all patterns of sleep polysomnogram signals to a small number of yes-or-no variables labeled wake or a stage of sleep (e.g., W, N1, N2, N3, and R for wake, the first, second, and third stages of non-rapid eye movement sleep and rapid eye movement sleep, respectively). However, the neurobiological underpinnings of such stages remained to be elucidated. We tried to evaluate their link to scores on the first and second principal components of the EEG spectrum (1PCS and 2PCS), the markers of two major groups of promoters/inhibitors of sleep/wakefulness delineated as the drives for sleep and wake, respectively. On two occasions, polysomnographic records were obtained from 69 university students during 50-min afternoon naps and 30-s stage epochs were assigned to 1PCS and 2PCS. Results suggested two dimensionality of the structure of individual differences in amounts of stages. Amount of N1 loaded exclusively on one of two dimensions associated with 1PCS, amounts of W and N2 loaded exclusively on another dimension associated with 2PCS, and amount of N3 was equally loaded on both dimensions. Scores demonstrated stability within each stage, but a drastic change in just one of two scores occurred during transitions from one stage to another on the way from wakefulness to deeper sleep (e.g., 2PCS changed from >0 to 0 during transition N1!N2). Therefore, the transitions between stages observed during short naps might be linked to rapid changes in the reciprocal interactions between the promoters/inhibitors of sleep/wakefulness. NEW & NOTEWORTHY In the present nap study, two dimensionality of the structure of individual differences in sleep stages was revealed. These results also suggested that individual variation in the sleep and wake drives associated with the first and second principal components of the EEG spectrum might underlie this structure. It seemed that each stage might be related to a certain, stage-specific combination of wake-sleep promoting/inhibiting influences associated with these drives for sleep and wake. 0022-3077/21 Copyright © 2021 the American Physiological Society

Sleep latency in poor nappers under exposure to weak 2-Hz and 8-Hz electromagnetic fields

It was hypothesized that human sleep might respond to the fields emitted by such natural sources as magnetic activity of the sun and the earth’s magnetic fields. However, the experiments aimed on testing this hypothesis remain scarce. Previously, we found an increase in the amounts of stages N2 or N3 during napping of good sleepers under exposure to low-level (0.004 μT) electromagnetic fields of frequencies 1 Hz or 2 Hz. It remains unexplored whether these fields might additionally decrease latency to stage N1. In this study, we selected 13 people with falling asleep problems to examine the effects of low-level electromagnetic fields on sleep latency. Sleep of these study participants was polysomnographically recorded during three 50-min afternoon napping attempts, either with exposure to either 2 Hz/0.004 μT or 8 Hz/0.004 μT electromagnetic fields or without exposure. We did not find that the sham exposure differed from the 2 Hz and 8 Hz exposures in latency to N1, while latency to N2 after the sham exposure was even shorter than after either the 2 Hz or 8 Hz exposure. We concluded that, although the effects of tested fields might be beneficial for sleep intensity (e.g., due to prolongation of N3), they might not be additionally effective against the falling asleep problems. © 2021 Informa UK Limited, trading as Taylor & Francis Group

Effects of exposures to weak 2-Hz vs. 8-Hz electromagnetic fields on spectral characteristics of the electroencephalogram in afternoon nap

The human brain seems to be able to respond to low-level extremely low-frequency electromagnetic fields. Controlled laboratory studies of human sleep under exposure to such fields are scarce, especially on the effects of 1 Hz–16 Hz fields overlapping with the frequencies of the electroencephalographic (EEG) signal (e.g., delta, theta, alpha, and sigma activities). In a double-blind placebo-controlled study, we examined the effects of exposure to low-level electromagnetic fields of frequencies 2 Hz and 8 Hz on the EEG power density spectra in the range from 1 Hz to 16 Hz and sleep structure. Sleep of 14 young healthy volunteers was polysomnographically recorded during three 50-min afternoon naps (either without exposure or with 2 Hz/0.004 μT or 8 Hz/0.004 μT electromagnetic field). During the first 30 min of a nap the sham, 2 Hz or 8 Hz/0.004 μT exposures had the same effect. For the remaining 20 min, amount of stage 3 sleep and powers in 1 Hz-8 Hz range continued to build up under the 8 Hz/0.004μT and, especially, under the 2 Hz/0.004 μT exposure, whereas they did not change in the sham condition. Therefore, the low-level 2 Hz electromagnetic fields might stimulate deep sleep in the afternoon nap. © 2020 Informa UK Limited, trading as Taylor & Francis Group

An hour in the morning is worth two in the evening: association of morning component of morningness–eveningness with single nucleotide polymorphisms in circadian clock genes

Sub-constructs of morning–evening preference might be differentially related to polymorphisms in circadian clock genes. We previously reported significant association between a single nucleotide polymorphism in PER3 (rs2640909) and Morning but not Evening Lateness scale of the Sleep–Wake Pattern Assessment Questionnaire. To further explore such a scale-specific relationship, seven single nucleotide polymorphisms in five circadian clock genes were studied using exploratory and confirmatory samples (in total, n = 698). The association of rs2640909 with Morning Lateness scale was not replicated in the confirmatory sample but remained significant in the merged sample. Moreover, we found and confirmed an association of this scale with rs1159814 in RORα. The results provided further evidence for differential relationship of polymorphisms in circadian clock genes with morning and evening components of morning–evening preference. We also suggested possibility to take into account the pattern of geographic variation in allele frequency for prioritization of circadian clock polymorphisms in candidate gene studies. © 2017 Informa UK Limited, trading as Taylor & Francis Group

An hour in the morning is worth two in the evening: association of morning component of morningness–eveningness with single nucleotide polymorphisms in circadian clock genes

Sub-constructs of morning–evening preference might be differentially related to polymorphisms in circadian clock genes. We previously reported significant association between a single nucleotide polymorphism in PER3 (rs2640909) and Morning but not Evening Lateness scale of the Sleep–Wake Pattern Assessment Questionnaire. To further explore such a scale-specific relationship, seven single nucleotide polymorphisms in five circadian clock genes were studied using exploratory and confirmatory samples (in total, n = 698). The association of rs2640909 with Morning Lateness scale was not replicated in the confirmatory sample but remained significant in the merged sample. Moreover, we found and confirmed an association of this scale with rs1159814 in RORα. The results provided further evidence for differential relationship of polymorphisms in circadian clock genes with morning and evening components of morning–evening preference. We also suggested possibility to take into account the pattern of geographic variation in allele frequency for prioritization of circadian clock polymorphisms in candidate gene studies. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Physicochemical properties and biological activity of the water depleted of heavy isotopes

Data on physicochemical properties of the light water (deuterium concentration is reduced to the ratio D/H = 4 ppm and that of the isotope of oxygen 18-to the ratio 18O/16O = 750 ppm) have been obtained. They include the melting and boiling points, kinematic viscosity, density, the spin-spin proton relaxation time, self-diffusion coefficients, and the small-angle laser light scattering. It was found out that the biological activity of the light water was determined by the mechanisms different from the ligand-induced toxic effects. An explanation was proposed for the detected significant changes of the light water as compared with the high-resistivity water having geochemically ordinary isotope composition. This explanation was based on the mechanism of formation of supramolecular density inhomogeneities in water representing the deuterium-stabilized heterophase clusters. © 2011 Allerton Press, Inc

Physicochemical properties and biological activity of the water depleted of heavy isotopes

Data on physicochemical properties of the light water (deuterium concentration is reduced to the ratio D/H = 4 ppm and that of the isotope of oxygen 18-to the ratio 18O/16O = 750 ppm) have been obtained. They include the melting and boiling points, kinematic viscosity, density, the spin-spin proton relaxation time, self-diffusion coefficients, and the small-angle laser light scattering. It was found out that the biological activity of the light water was determined by the mechanisms different from the ligand-induced toxic effects. An explanation was proposed for the detected significant changes of the light water as compared with the high-resistivity water having geochemically ordinary isotope composition. This explanation was based on the mechanism of formation of supramolecular density inhomogeneities in water representing the deuterium-stabilized heterophase clusters. © 2011 Allerton Press, Inc