Alterations of spectral parameters of rat brain electrical activity after sciatic nerve section

Changes in electrophysiological brain characteristics accompanying the development of neurogenic pain syndrome induced by transsection of sciatic nerve were analyzed. At the maximum pain syndrome 3 weeks after the deafferentation, a reorganization of the brain electrical activity was observed in the limbic structures (hippocampus, amygdale, and nucleus accumbens), frontal cortex, and the caudate putamen. An increase in the relative spectral power of the delta and alpha bands and a decrease in the relative power of the beta2 band (as compared to baseline activity) took place. Alteration of the electrical activity in the limbic structures did not depend on manifestations of the neurogenic pain syndrome (autotomy). The increase in the relative spectral power of the alpha-band activity in all the structures under study suggests the involvement of the reticular thalamic nucleus in pathogenesis of neurogenic pain syndrome.     

Effect of immunizing rats with a serotonin-bovine serum albumin conjugate on the structure of diurnal sleep and electrical activity of the brain]

Rats were immunized with bovine serum albumin conjugated with 5-hydroxytriptamine (5-HT). Two injections with a 2-week interval were carried out. At first, rats were injected subcutaneously (2 mg/kg, 0.25 ml) with Freund's adjuvant complete. The second injections (10 mg/kg intraperitoneally) was made 2 weeks later without the adjuvant. One week after the first antigen injection, there were a decrease in the relative power of the electrical activity of the caudate putamen, neocortex, and amygdala in the delta 2 and theta 2 bands and its increase in the alpha and beta-ranges. The number and duration (total and mean) of REM sleep episodes as well as REM sleep contribution in the total sleep duration decreased. These findings testify to a reduced functional activity of the central serotonergic system. Four-five weeks after the first injection, a tendency to a recovery of the bio-electrical spectral pattern and diurnal sleep structure was revealed. Five weeks after the first antigen injection, the titre of antibodies to 5-HT was 1:32-1:64.     

Alteration in the brain electrical activity, diurnal sleep structure, and the rat behavior after immunization with bovine serum albumin conjugated with dopamine

Male Wistar rats (380-430 g) were immunized with bovine serum albumin conjugated with dopamine (2 mg/kg, 0.25 ml) mixed with Freund's adjuvant complete (0.25 ml) or with bovine serum albumin mixed with Freund's adjuvant complete in the same doses. One week after the immunization with bovine serum albumin conjugated with dopamine, irregular spike activity and high-amplitude spindles associated with the state of awake immobility were recorded in the rat neocortex and caudate putamen, the relative power of the electrical activity in the caudate putamen was decreased in the alpha band, while the relative power of the beta 1 in the cortical EEG was increased. In the structure of 4-hour diurnal sleep, a decrease in the mean duration of sleep episodes and a reduction in the REM sleep content were observed. The parameters of the electrical activity and diurnal sleep structure returned to normal during the following 4 weeks. The open-field behavior 2 weeks after the second immunization (without Freund's adjuvant complete) did not differ from that of the control rats immunized only with bovine serum albumin. Titres of antibodies to dopamine after the second antigen injection were 1:32-1:64 in the electrophysiological series and 1:128-1:256 in behavioral experiments.     

Pre-stimulus spectral EEG patterns and the visual evoked response

The relationship between the latencies and amplitudes of the N1 and P2 components of the visual evoked potential (VEP) and the psychophysiological state of the brain immediately preceding the time of the stimulus has been investigated in 7 male subjects. Power spectral measures in the delta, theta, alpha and beta bands of the 1 sec pre-stimulus EEG were used to assess the brain state, and low intensity flashes, delivered randomly between 2 and 6 whole seconds, were used as the stimuli. Trials were ranked separately according to the relative amounts of pre-stimulus power in each EEG band and were partitioned into groups by an equal pre-stimulus spectral power criterion. Averaged EPs were computed from these groups and multiple regression analysis was used to relate pre-stimulus spectral power values to EP features. Five of the 7 subjects displayed consistent increases in N1-P2 amplitude as a function of increasing pre-stimulus relative alpha power. The between-subjects effect of pre-stimulus EEG on N1 latency was small, but was moderate for P2 latency (both significant). Both N1 and P2 latency were found to decrease with increasing amounts of pre-stimulus relative delta and theta power.     

电针对实验性癫痫发作的影响：脑电的功率谱分析

以电惊厥和青霉素致痫作为实验性癲痫的动物模型。采用脑电的计算机功率谱分析技术,研究了电针作用于发作过程中脑电各频段功率百分比的变化。在安静的大鼠,脑电以δ和θ频段为主,其功率主峰在δ频段。青霉素致痫和电惊厥使δ频段功率百分比下降,α和β频段功率百分比增加,主功率频段右移,总功率亦大大增强。本实验采用的电针对背景脑电活动没有明显影响。而电针加电惊厥或青霉素致痫,δ频段功率百分比复又增加,α和β频段功率百分比则下降,主功率频段又回到δ频段,总功率也显著减少。压缩功率谱阵图直观地显示了这种变化。结果提示,电针可使大鼠脑电出现同步化趋势,可能是加强了脑的抑制过程,从而抑制了癲痫发作的。     

Spectral analysis of the heart rate variability in sleep

Spectral analysis of heart rate variability (HRV) during overnight polygraphic recording was performed in 11 healthy subjects. The total spectrum power, power of the VLF, LF and HF spectral bands and the mean R-R were evaluated. Compared to Stage 2 and Stage 4 non-REM sleep, the total spectrum power was significantly higher in REM sleep and its value gradually increased in the course of each REM cycle. The value of the VLF component (reflects slow regulatory mechanisms, e.g. the renin-angiotensin system, thermoregulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 of non-REM sleep. The LF spectral component (linked to the sympathetic modulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 non-REM sleep. On the contrary, a power of the HF spectral band (related to parasympathetic activity) was significantly higher in Stage 2 and Stage 4 non-REM than in REM sleep. The LF/HF ratio, which reflects the sympathovagal balance, had its maximal value during REM sleep and a minimal value in synchronous sleep. The LF/HF ratio significantly increased during 5-min segments of Stage 2 non-REM sleep immediately preceding REM sleep compared to 5-min segments of Stage 2 non-REM sleep preceding the slow-wave sleep. This expresses the sympathovagal shift to sympathetic predominance occurring before the onset of REM sleep. A significant lengthening of the R-R interval during subsequent cycles of Stage 2 non-REM sleep was documented, which is probably related to the shift of sympathovagal balance to a prevailing parasympathetic influence in the course of sleep. This finding corresponds to a trend of a gradual decrease of the LF/HF ratio in subsequent cycles of Stage 2 non-REM sleep.     

Focus: Sex and Gender Health: Tobacco Smoking and the Resting Maternal Brain: A Preliminary Study of Frontal EEG

Tobacco smoking has been attributed to a wide range of detrimental health consequences for both women and their children. In addition to its known physical health effects, smoking may also impact maternal neural responses and subsequent caregiving behavior. To begin investigating this issue, we employed electroencephalography (EEG) to examine resting neural oscillations of tobacco-smoking mothers (n = 35) and non-smoking mothers (n = 35). We examined seven EEG frequency bands recorded from frontal electrode sites (delta, theta, alpha, alpha₁, alpha₂, beta, and gamma). While no between-group differences were present in high-frequency bands (alpha₂, beta, gamma), smokers showed greater spectral power in low-frequency bands (delta, theta, alpha, alpha₁) compared to non-smokers. This increased power in low-frequency bands of tobacco-smoking mothers is consistent with a less aroused state and may be one mechanism through which smoking might affect the maternal brain and caregiving behavior.     

Involvement of the brain dopaminergic systems in the development of the MPTP-induced depressive state in rats

Depressive state was produced in Wistar rats by repeated intraperitoneal administration of proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) inducing death of brain dopaminergic neurons. Weight loss and increase in REM-sleep rate during diurnal sleep were considered to be signs of the development of an experimental depressive state. During the development of the depressive state of rats, the MPTP-induced reorganization of the spectral power of electrical activity was observed in the terminal fields of the nigrostriatal, mesocortical, and mesolimbic dopaminergic systems, amygdala, and hippocampus. The most pronounced changes were revealed in the terminal field of the nigrostriatal system and hippocampus. The reorganization of the spectral power in the thetal and theta2 bands in the hippocampus and dopaminergic structures suggests the involvement of the hippocampus in producing changes in the emotional state during development of the MPTP-induced depressive syndrome.     

The Relationship between Brain Morphology and Polysomnography in Healthy Good Sleepers

BackgroundNormal sleep continuity and architecture show remarkable inter-individual variability. Previous studies suggest that brain morphology may explain inter-individual differences in sleep variables.MethodThirty-eight healthy subjects spent two consecutive nights at the sleep laboratory with polysomnographic monitoring. Furthermore, high-resolution T1-weighted MRI datasets were acquired in all participants. EEG sleep recordings were analyzed using standard sleep staging criteria and power spectral analysis. Using the FreeSurfer software for automated segmentation, 174 variables were determined representing the volume and thickness of cortical segments and the volume of subcortical brain areas. Regression analyses were performed to examine the relationship with polysomnographic and spectral EEG power variables.ResultsThe analysis did not provide any support for the a-priori formulated hypotheses of an association between brain morphology and polysomnographic variables. Exploratory analyses revealed that the thickness of the left caudal anterior cingulate cortex was positively associated with EEG beta2 power (24–32 Hz) during REM sleep. The volume of the left postcentral gyrus was positively associated with periodic leg movements during sleep (PLMS).ConclusionsThe function of the anterior cingulate cortex as well as EEG beta power during REM sleep have been related to dreaming and sleep-related memory consolidation, which may explain the observed correlation. Increased volumes of the postcentral gyrus may be the result of increased sensory input associated with PLMS. However, due to the exploratory nature of the corresponding analyses, these results have to be replicated before drawing firm conclusions.     

Electrical activity of the rat brain following antenatal hypoxia

EEG and EPs in the visual and parietal neocortical areas and the hippocampus were studied in freely behaving rats at the age of two-three months after antenatal hypoxia. Increase of spectral power in delta and theta bands and its decrease in alpha and beta bands in the background EEG and in responses to a protracted light stimulation were observed in experimental animals in comparison to control ones. The most pronounced changes were observed in the parietal cortex and hippocampus. The character of changes in latencies and the share of individual EP components recorded point to an accelerated excitation reverberation in neuronal networks in response to afferent stimuli and to a prolongation of after-discharges in the parietal cortex and hippocampus testifying to peculiarity of information processing in these brain structures. On the basis of other authors' data, certain parallelism is supposed to exist between the electrophysiological parameters in experimental animals and some groups of children with mental retardation.     

The maturational trajectories of NREM and REM sleep durations differ across adolescence on both school-night and extended sleep

We recorded sleep electroencephalogram longitudinally across ages 9-18 yr in subjects sleeping at home. Recordings were made twice yearly on 4 consecutive nights: 2 nights with the subjects maintaining their ongoing school-night schedules, and 2 nights with time in bed extended to 12 h. As expected, school-night total sleep time declined with age. This decline was entirely produced by decreasing non-rapid eye movement (NREM) sleep. Rapid eye movement (REM) sleep durations increased slightly but significantly. NREM and REM sleep durations also exhibited different age trajectories when sleep was extended. Both durations exceeded those on school-night schedules. However, the elevated NREM duration did not change with age, whereas REM durations increased significantly. We interpret the adolescent decline in school-night NREM duration in relation to our hypothesis that NREM sleep reverses changes produced in plastic brain systems during waking. The "substrate" produced during waking declines across adolescence, because synaptic elimination decreases the intensity (metabolic rate) of waking brain activity. Declining substrate reduces both NREM intensity (i.e., delta power) and NREM duration. The absence of a decline in REM sleep duration on school-night sleep and its age-dependent increase in extended sleep pose new challenges to understanding its physiological role. Whatever their ultimate explanation, these robust findings demonstrate that the two physiological states of human sleep respond differently to the maturational brain changes of adolescence. Understanding these differences should shed new light on both brain development and the functions of sleep.     

Salubrinal, an inhibitor of protein synthesis, promotes deep slow wave sleep

Previous work showed that sleep is associated with increased brain protein synthesis and that arrest of protein synthesis facilitates sleep. Arrest of protein synthesis is induced during the endoplasmic reticulum (ER) stress response, through phosphorylation of eukaryotic initiation factor 2alpha (p-eIF2alpha). We tested a hypothesis that elevation of p-eIF2alpha would facilitate sleep. We studied the effects of intracerebroventricular infusion of salubrinal (Salub), which increases p-eIF2alpha by inhibiting its dephosphorylation. Salub increased deep slow wave sleep by 255%, while reducing active waking by 49%. Delta power within non-rapid eye movement (NREM) sleep was increased, while power in the sigma, beta, and gamma bands during NREM was reduced. We found that Salub increased expression of p-eIF2alpha in the basal forebrain (BF) area, a sleep-wake regulatory brain region. Therefore, we quantified the p-eIF2alpha-immunolabeled neurons in the BF area; Salub administration increased the number of p-eIF2alpha-expressing noncholinergic neurons in the caudal BF. In addition, Salub also increased the intensity of p-eIF2alpha expression in both cholinergic and noncholinergic neurons, but this was more widespread among the noncholinergic neurons. Our findings support a hypothesis that sleep is facilitated by signals associated with the ER stress response.     

Low-dose oral risperidone lengthened sleep duration in healthy participants

We examined the effects of low-dose oral risperidone (RIS) on nocturnal sleep in healthy participants. This study was performed in a placebo-controlled manner in 10 healthy male volunteers (mean age, 23.6 years), with administration of 0.5 mg of RIS oral solution or a placebo in the morning or evening for 2 consecutive days. Each night, polysomnography (PSG) was performed, and PSG data during non-rapid-eye movement (REM) sleep were processed by power spectral analysis. An evening administration of 0.5 mg RIS significantly increased total sleep time, sleep efficiency and sleep stage 3, and significantly decreased total waking time and waking after sleep onset (P < 0.05). A morning administration of 0.5 mg RIS significantly increased sleep stage 3 (P < 0.05). According to power spectral analysis, the evening administration of RIS significantly increased the theta power (P < 0.05) and decreased the beta power (P < 0.05) during non-REM sleep. The administration of 0.5 mg oral RIS increases sleep stage 3 and increases total sleep time following evening administration.

     

Development of examination stress in subjects with various levels of cortical activation

The work is aimed at the study of neurophysiological mechanisms of examination stress in subjects with different levels of cortical activation. Spectral power and typical cortical connections of EEG rhythms were studied in students under conditions of stress before and immediately after examination as well as during usual academic semester. Students with relatively higher and relatively lower baseline alpha rhythm, i.e., with different levels of cortical activation revealed both similar and different EEG reactions. Before examination, in both groups of subjects the spectral power of EEG activity in the delta and thetal bands increased, and the number of connections in the bands of the alpha and beta 1 rhythms decreased as compared to usual baseline conditions. However, the EEG reactions in the theta 2 band in the two groups were oppositely directed. Significant changes in the beta 2 power were observed only in the group of subjects with higher baseline level of cortical activation.     

Psychophysiological correlates of lucid dreaming.

The main goal of the present study was to explore electrophysiological differences between lucid and nonlucid dreams in REM sleep. Seven men and four women experienced in lucid dreaming underwent polysomnographic recordings in the sleep laboratory on two consecutive nights. EEG signals were subjected to spectral analysis to obtain five different frequency bands between 1 and 20 Hz. Lucidity was determined by both subjective dream reports and eye-movement signals made by the subjects in response to light stimuli indicating a REM period. The main discrimination factor between lucid and nonlucid dreaming was found in the beta-1 frequency band (13-19 Hz), which in lucid dreaming was increased in both parietal regions. The ratio of frontal to parietal beta-1 activity was 1 to 1.16 in nonlucid and 1 to 1.77 in lucid dreaming. A tendency towards the greatest increase was observed in the left parietal lobe (P3), an area of the brain considered to be related to semantic understanding and self-awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain oscillatory activity during sleep shows unknown dysfunctions in early encephalopathy

Electroencephalographic recordings in cirrhotic patients without overt hepatic encephalopathy (HE) have mainly been performed during wakefulness. Our aim was to quantify their alterations in nocturnal sleep electroencephalogram (EEG). In 20 patients and 20 healthy volunteers, we recorded a nocturnal digital polysomnography. Different sleep parameters were measured. Besides, we performed quantitative analysis of EEG (qEEG) as follows: spectral power in the different sleep stages was calculated in the frequency bands low δ, δ, θ, α, and σ. Also, the mean dominant frequency and Sleep Indexes were obtained. In comparison with controls, the group of patients showed (1) different alterations in both the microstructure and the macrostructure of sleep; (2) an increase in, both, θ band power and the average mean dominant frequency during rapid eye movement (REM); (3) in all sleep stages, a decrease of sleep electroencephalogram spectral power in low δ band and an increase in δ band: and (4) in stages N3 and REM, significant increases in the minimum of mean dominant frequency and in the respective sleep indexes. Therefore, in cirrhotic patients without overt HE, and likely having minimal hepatic encephalopathy, we found different alterations in both the microstructure and the macrostructure of nocturnal sleep. Also, sleep qEEG showed a brain dysfunction in slow oscillatory mechanisms intrinsic of sleep stages, with an increase in the frequency of its maximal electroencephalogram synchronization, from low δ to δ band. These alterations may reflect the onset of encephalopathy; sleep qEEG may, thus, be an adequate tool for its brain functional evaluation and follow-up.     

完全睡眠剥夺对大脑注意网络冲突效应和脑电样本熵的影响*

目的: 本研究分析睡眠剥夺对个体选择性注意网络冲突效应和脑电样本熵的影响,探讨睡眠剥夺对大脑注意网络的影响。方法: 25名健康受试者参与36 h完全睡眠剥夺试验。试验于当天9:00开始,于次日21:00结束,试验采用自身前后对照设计。受试者在睡眠剥夺前后分别完成注意网络任务,同步采集受试者的脑电图。用脑电样本熵算法分析脑电图的delta、theta、alpha、beta和gamma频率段的脑电复杂度并对比各频段脑电样本熵在睡眠剥夺前、后的变化。结果: 同睡眠剥夺前比较,睡眠剥夺后与受试者的注意网络冲突效应密切相关的反应时显著下降(P＜0.01),正确率显著增加(P＜0.01)。脑电样本熵分析发现在beta频率段,与注意网络冲突控制相关的脑电样本熵值在睡眠剥夺后明显增大(P＜0.01)。其余脑电频率段脑电样本熵未发现显著差异。结论: 表明完全睡眠剥夺后大脑的注意网络冲突效应降低,表明睡眠剥夺后执行冲突控制能力的下降。     

Correlation between ventilation and brain blood flow during hypoxic sleep

Ventilation and brain blood flow (BBF) were simultaneously measured during carbon monoxide (CO) inhalation in awake and sleeping goats up to HbCO levels of 40%. Unilateral BBF, which was continuously measured with an electromagnetic flow probe placed around the internal maxillary artery, progressively increased with CO inhalation in the awake and both sleep stages. The increase in BBF with CO inhalation during rapid-eye-movement (REM) sleep (delta BBF/delta arterial O2 saturation = 1.34 +/- 0.27 ml X min-1 X %-1) was significantly greater than that manifested during wakefulness (0.87 +/- 0.14) or slow-wave sleep (0.92 +/- 0.13). Ventilation was depressed by CO inhalation during both sleep stages but was unchanged from base-line values in awake goats. In contrast to slow-wave (non-REM) sleep, the ventilatory depression of REM sleep was primarily due to a reduction in tidal volume. Since tidal volume is more closely linked to central chemoreceptor function, we believe that these data suggest a possible role of the increased cerebral perfusion during hypoxic REM sleep. Induction of relative tissue alkalosis at the vicinity of the medullary chemoreceptor may contribute to the ventilatory depression exhibited during this sleep period.     

Transitions from Wakefulness to Sleep at Different Times of Day: Old vs. Young Subjects

In order to assess age effects upon the daytime level of alertness, both subjective and objective measures of alertness were obtained in 19 healthy elderly males (mean age 65 years) and 19 healthy young males (mean age 21 years). Subjects were recorded during a Multiple Sleep Latency Test (MSLT), administered at 5 different times of day (9 a.m., 12 a.m., 3 p.m., 6 p.m., 9 p.m.). Before each test, subjects filled out an alertness questionnaire. During the entire 20 minutes of each test electroencephalographic (EEG) recordings were made and transformed into 40 averaged spectra, one for each 30 s epoch. For the delta, theta, alpha, sigma and beta bands of the EEG 6 consecutive values were averaged to obtain 1 value per 3 minutes. On the basis of the visually guided detection of the first spindle, sleep onset was determined. The elderly subjects obtained a higher overall level of subjective alertness than the young subjects. No age effect was observed for sleep latency, which followed a U-shaped diurnal trend. Overall, the mean relative EEG energy values followed a diurnal trend that was the reverse of that for sleep latency. The mean relative delta EEG energy gradually increased, and the mean relative alpha EEG energy gradually decreased across the MSLT. For the young subjects the respective ranges of variation of these EEG bands were very similar, while for the elderly subjects the range of variation of the alpha values was less than half of that for the delta band. Apparently, alpha EEG activity during the wake-sleep transition does not simply covary with delta EEG activity. Moreover, age appears to have a significant effect upon the dynamics of alpha EEG activity during the wake-sleep transition.     

Alpha Reactivity to Complex Sounds Differs during REM Sleep and Wakefulness

We aimed at better understanding the brain mechanisms involved in the processing of alerting meaningful sounds during sleep, investigating alpha activity. During EEG acquisition, subjects were presented with a passive auditory oddball paradigm including rare complex sounds called Novels (the own first name - OWN, and an unfamiliar first name - OTHER) while they were watching a silent movie in the evening or sleeping at night. During the experimental night, the subjects’ quality of sleep was generally preserved. During wakefulness, the decrease in alpha power (8–12 Hz) induced by Novels was significantly larger for OWN than for OTHER at parietal electrodes, between 600 and 900 ms after stimulus onset. Conversely, during REM sleep, Novels induced an increase in alpha power (from 0 to 1200 ms at all electrodes), significantly larger for OWN than for OTHER at several parietal electrodes between 700 and 1200 ms after stimulus onset. These results show that complex sounds have a different effect on the alpha power during wakefulness (decrease) and during REM sleep (increase) and that OWN induce a specific effect in these two states. The increased alpha power induced by Novels during REM sleep may 1) correspond to a short and transient increase in arousal; in this case, our study provides an objective measure of the greater arousing power of OWN over OTHER, 2) indicate a cortical inhibition associated with sleep protection. These results suggest that alpha modulation could participate in the selection of stimuli to be further processed during sleep.