Changes in electroencephalographic microstates between evening and morning are associated with overnight sleep slow waves in healthy individuals

STUDY OBJECTIVES

Microstates are semi-stable voltage topographies that account for most of electroencephalogram (EEG) variance. However, the impact of time of the day and sleep on microstates has not been examined. To address this gap, we assessed whether microstates differed between the evening and morning and whether sleep slow waves correlated with microstate changes in healthy participants.

METHODS

Forty-five healthy subjects were recruited. Each participant underwent six minutes of resting state EEG recordings in the evening and morning, interleaved by sleep EEGs. Evening-to-morning changes in microstate duration, coverage, and occurrence were assessed. Furthermore, correlation between microstate changes and sleep slow-wave activity (SWA) and slow-wave density (SWD) were performed.

RESULTS

Two-way ANOVAs with Microstate Class (A, B, C, and D) and Time (evening and morning) revealed significant Microstate Class*Time interaction for duration (F(44) = 5.571, p = 0.002), coverage (F(44) = 6.833, p = 0.001), and occurrence (F(44) = 5.715, p = 0.002). Post-hoc comparisons showed significant effects for microstate C duration (padj=0.048, Cohen's d = -0.389), coverage (padj=0.002, Cohen's d = -0.580), and occurrence (padj=0.002, Cohen's d= -0.606). Topographic analyses revealed inverse correlations between SWD, but not SWA, and evening-to-morning changes in microstate C duration (r = - 0.51, padj = 0.002), coverage (r = - 0.45, padj = 0.006), and occurrence (r = - 0.38, padj = 0.033).

CONCLUSION

Microstate characteristics showed significant evening-to-morning changes associated with, and possibly regulated by, sleep slow-waves. These findings suggest that future microstate studies should control for time of day and sleep effects.

N-Acetylaspartate and Choline Metabolites in Cortical and Subcortical Regions in Clinical High Risk Relative to Healthy Control Subjects: An Exploratory 7T MRSI Study

N-acetylaspartate (NAA) and choline (Cho) are two brain metabolites implicated in several key neuronal functions. Abnormalities in these metabolites have been reported in both early course and chronic patients with schizophrenia (SCZ). It is, however, unclear whether NAA and Cho's alterations occur even before the onset of the disorder. Clinical high risk (CHR) individuals are a population uniquely enriched for psychosis and SCZ. In this exploratory study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to examine differences in total NAA (tNAA; NAA + N-acetylaspartylglutamate [NAAG]) and major choline-containing compounds, including glycerophosphorylcholine and phosphorylcholine [tCho], over the creatine (Cre) levels between 26 CHR and 32 healthy control (HC) subjects in the subcortical and cortical regions. While no tCho/Cre differences were found between groups in any of the regions of interest (ROIs), we found that CHR had significantly reduced tNAA/Cre in the right dorsal lateral prefrontal cortex (DLPFC) compared to HC, and that the right DLPFC tNAA/Cre reduction in CHR was negatively associated with their positive symptoms scores. No tNAA/Cre differences were found between CHR and HC in other ROIs. In conclusion, reduced tNAA/Cre in CHR vs. HC may represent a putative molecular biomarker for risk of psychosis and SCZ that is associated with symptom severity.

Natural Oscillatory Frequency Slowing in the Premotor Cortex of Early-Course Schizophrenia Patients: A TMS-EEG Study

Despite the heavy burden of schizophrenia, research on biomarkers associated with its early course is still ongoing. Single-pulse Transcranial Magnetic Stimulation coupled with electroencephalography (TMS-EEG) has revealed that the main oscillatory frequency (or "natural frequency") is reduced in several frontal brain areas, including the premotor cortex, of chronic patients with schizophrenia. However, no study has explored the natural frequency at the beginning of illness. Here, we used TMS-EEG to probe the intrinsic oscillatory properties of the left premotor cortex in early-course schizophrenia patients (<2 years from onset) and age/gender-matched healthy comparison subjects (HCs). State-of-the-art real-time monitoring of EEG responses to TMS and noise-masking procedures were employed to ensure data quality. We found that the natural frequency of the premotor cortex was significantly reduced in early-course schizophrenia compared to HCs. No correlation was found between the natural frequency and age, clinical symptom severity, or dose of antipsychotic medications at the time of TMS-EEG. This finding extends to early-course schizophrenia previous evidence in chronic patients and supports the hypothesis of a deficit in frontal cortical synchronization as a core mechanism underlying this disorder. Future work should further explore the putative role of frontal natural frequencies as early pathophysiological biomarkers for schizophrenia.

Personal and situational variables associated with wind turbine noise annoyance

The possibility that wind turbine noise (WTN) affects human health remains controversial. The current analysis presents results related to WTN annoyance reported by randomly selected participants (606 males, 632 females), aged 18-79, living between 0.25 and 11.22 km from wind turbines. WTN levels reached 46 dB, and for each 5 dB increase in WTN levels, the odds of reporting to be either very or extremely (i.e., highly) annoyed increased by 2.60 [95% confidence interval: (1.92, 3.58), p < 0.0001]. Multiple regression models had R(2)'s up to 58%, with approximately 9% attributed to WTN level. Variables associated with WTN annoyance included, but were not limited to, other wind turbine-related annoyances, personal benefit, noise sensitivity, physical safety concerns, property ownership, and province. Annoyance was related to several reported measures of health and well-being, although these associations were statistically weak (R(2 )< 9%), independent of WTN levels, and not retained in multiple regression models. The role of community tolerance level as a complement and/or an alternative to multiple regression in predicting the prevalence of WTN annoyance is also provided. The analysis suggests that communities are between 11 and 26 dB less tolerant of WTN than of other transportation noise sources.

ICBEN review of research on the biological effects of noise 2011-2014

The mandate of the International Commission on Biological Effects of Noise (ICBEN) is to promote a high level of scientific research concerning all aspects of noise-induced effects on human beings and animals. In this review, ICBEN team chairs and co-chairs summarize relevant findings, publications, developments, and policies related to the biological effects of noise, with a focus on the period 2011-2014 and for the following topics: Noise-induced hearing loss; nonauditory effects of noise; effects of noise on performance and behavior; effects of noise on sleep; community response to noise; and interactions with other agents and contextual factors. Occupational settings and transport have been identified as the most prominent sources of noise that affect health. These reviews demonstrate that noise is a prevalent and often underestimated threat for both auditory and nonauditory health and that strategies for the prevention of noise and its associated negative health consequences are needed to promote public health.

Road traffic noise and annoyance: a quantification of the effect of quiet side exposure at dwellings

Previous studies indicate that residents may benefit from a “quiet side” to their dwellings. The influence of the level of road traffic noise exposure at the least exposed side on road traffic noise annoyance was studied in Amsterdam, The Netherlands. Road traffic noise exposure was assessed at the most and least exposed façade (L_den,most and L_den,least respectively) of dwellings for subjects in a population based survey (N = 1,967). It was investigated if and to what extent relative quietness at the least exposed façade affected the level of road traffic noise annoyance by comparing two groups: (1) The subgroup with a relatively quiet façade; (2) the subgroup without a relatively quiet façade (large versus small difference in exposure between most and least exposed façade; DIF ≥ 10 dB and DIF < 10 dB respectively). In addition, it was investigated if and to what extent L_den,least affected the level of road traffic noise annoyance. Results indicate a significantly lower road traffic noise annoyance score at a given L_den,most, in the subgroup with DIF ≥ 10 dB versus DIF < 10 dB. Furthermore, results suggest an effect of L_den,least independent of L_den,most. The estimated size of the effect expressed in an equivalent change in L_den,most approximated 5 dB for both the difference between the two subgroups (DIF ≥ 10 dB and DIF < 10 dB), and for a 10 dB change in L_den,least.

The effect of pain-related fear on sexual arousal in women with superficial dyspareunia

The role of pain-related fear in the etiology and/or maintenance of superficial dyspareunia is still unclear. The objective of this experiment was to investigate the effects of pain-related fear on sexual arousal in women with superficial dyspareunia (n=48) and women without sexual complaints (n=48). To induce pain-related fear, participants were told that they had a 60% chance of receiving painful stimuli while being exposed to one of two erotic film clips. Genital arousal was assessed using vaginal photoplethysmography. Self-reported ratings of genital sensations and affect were collected after both erotic stimulus presentations. Elevated levels of skin conductance and higher ratings of experienced threat during the pain threat condition indicated that fear was successfully elicited. Pain-related fear impeded genital arousal in all women. Women of both groups reported significantly less positive affect and more negative affect when threatened. Although women with dyspareunia did not differ in their genital responsiveness from women without sexual complaints, they experienced overall significantly more negative affect than the control group. The present results indicate that pain-related fear reduces genital and subjective sexual responding in women with and without sexual problems. We conclude that emotional appraisal of the sexual situation determines genital responsiveness in both sexually dysfunctional and functional women.

A comparison between exposure-response relationships for wind turbine annoyance and annoyance due to other noise sources

Surveys have shown that noise from wind turbines is perceived as annoying by a proportion of residents living in their vicinity, apparently at much lower noise levels than those inducing annoyance due to other environmental sources. The aim of the present study was to derive the exposure-response relationship between wind turbine noise exposure in L(den) and the expected percentage annoyed residents and to compare it to previously established relationships for industrial noise and transportation noise. In addition, the influence of several individual and situational factors was assessed. On the basis of available data from two surveys in Sweden (N=341, N=754) and one survey in the Netherlands (N=725), a relationship was derived for annoyance indoors and for annoyance outdoors at the dwelling. In comparison to other sources of environmental noise, annoyance due to wind turbine noise was found at relatively low noise exposure levels. Furthermore, annoyance was lower among residents who received economical benefit from wind turbines and higher among residents for whom the wind turbine was visible from the dwelling. Age and noise sensitivity had similar effects on annoyance to those found in research on annoyance by other sources.

Urban road traffic noise and annoyance: the effect of a quiet façade

Road traffic noise in urban areas is a major source of annoyance. A quiet façade has been hypothesized to beneficially affect annoyance. However, only a limited number of studies investigated this hypothesis, and further quantification is needed. This study investigates the effect of a relatively quiet façade on the annoyance response. Logistic regression was performed in a large population based study (GLOBE, N~18,000), to study the association between road traffic noise exposure at the most exposed dwelling façade (L(den)) and annoyance in: (1) The subgroup with a relatively quiet façade (large difference in road traffic noise level between most and least exposed façade (Q>10 dB); (2) the subgroup without a relatively quiet façade (Q<10 dB). Questionnaire data were linked to individual exposure assessment based on detailed spatial data (GIS) and standard modeling techniques. Annoyance was less likely (OR(Q) (>10)<OR(Q) (<10)) in the subgroup with relatively quiet façade compared to the subgroup without relatively quiet façade. The difference in response between groups seemed to increase with increasing Q and L(den). Results indicate that residents may benefit from a quiet façade to the dwelling.

Practical ranges of loudness levels of various types of environmental noise, including traffic noise, aircraft noise, and industrial noise

In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noise signal varies considerably with the shape of the frequency spectrum of the noise signal. In particular the bandwidth of the spectrum has a large effect on the loudness level, due to the effect of critical bands in the human hearing system. The low-frequency content of the spectrum also has an effect on the loudness level. In this note the relation between loudness level and A-weighted sound level is analyzed for various environmental noise spectra, including spectra of traffic noise, aircraft noise, and industrial noise. From loudness levels calculated for these environmental noise spectra, diagrams are constructed that show the relation between loudness level, A-weighted sound level, and shape of the spectrum. The diagrams show that the upper limits of the loudness level for broadband environmental noise spectra are about 20 to 40 phon higher than the lower limits for narrowband spectra, which correspond to the loudness levels of pure tones. The diagrams are useful for assessing limitations and potential improvements of environmental noise control methods and policy based on A-weighted sound levels.

Trends in aircraft noise annoyance: the role of study and sample characteristics

Recently, it has been suggested that the annoyance of residents at a given aircraft noise exposure level increases over the years. The objective of the present study was to verify the hypothesized trend and to identify its possible causes. To this end, the large database used to establish earlier exposure-response relationships on aircraft noise was updated with original data from several recent surveys, yielding a database with data from 34 separate airports. Multilevel grouped regression was used to determine the annoyance response per airport, after which meta-regression was used to investigate whether study characteristics could explain the heterogeneity in annoyance response between airports. A significant increase over the years was observed in annoyance at a given level of aircraft noise exposure. Furthermore, the type of annoyance scale, the type of contact, and the response percentage were found to be sources of heterogeneity. Of these, only the scale factor could statistically account for the trend, although other findings rule it out as a satisfactory explanation. No evidence was found for increased self-reported noise sensitivity. The results are of importance to the applicability of current exposure-annoyance relationships for aircraft noise and provide a basis for decisions on whether these need to be updated.

Long-term road traffic noise exposure is associated with an increase in morning tiredness

This study investigates the association between night time road traffic noise exposure (L(night)) and self-reported sleep problems. Logistic regression was performed in a large population based cohort study (GLOBE), including over 18 000 subjects, to study the association between exposure at the dwelling facade and sleep problems. Measures of sleep problems were collected by questionnaire with two questions: "Do you in general get up tired and not well rested in the morning?" and "Do you often use sleep medication or tranquilizers?" After adjustment for potential confounders, a significant association was found between noise exposure and the risk of getting up tired and not rested in the morning. Although prevalence of medication use was higher at higher noise levels compared to the reference category (L(night)<35 dB), after adjustment for covariates this association was not significant. Long-term road traffic noise exposure is associated with increased risk of getting up tired and not rested in the morning in the general population. This result extends the earlier established relationship between long-term noise exposure and self-reported sleep disturbance assessed with questions that explicitly referred to noise and indicates that road traffic noise exposure during the night may have day-after effects.

Annoyance from environmental noise across the lifespan

Curvilinear effects of age on self-reported annoyance from environmental noise were investigated in a pooled international and a Dutch sample of in total 62,983 individuals aged between 15 and 102 years. All respondents were frequently exposed to varying levels of transportation noise (i.e., aircraft, road traffic, and railway noise). Results reveal an inverted U-shaped pattern, where the largest number of highly annoyed individuals was found in the middle-aged segment of the sample (peaking around 45 years) while the lowest number was found in the youngest and oldest age segments. This pattern was independent of noise exposure level and self-reported noise sensitivity. The inverted U-shape explains the absence of linear age effects in previous studies. The results are discussed in light of theories predicting an age-related vulnerability to noise.

The effects of failing to control pain: an experimental investigation

Chronic pain patients are often confronted with repeated failure to achieve pain relief. The aim of this study was to experimentally investigate the effects of repeated failing attempts to control pain on pain impact (pain intensity, emotional and physiological responses). Perceived control over an electrocutaneous pain stimulus was manipulated between subjects by success or failure feedback on a task by which control over pain could be acquired. In addition, success or failure at the task was manipulated without suggesting a possibility to control pain. It was hypothesized that successful control would lead to lowest pain impact, whereas failure to control pain would lead to even higher pain impact than absent control. Furthermore, it was hypothesized that failure feedback would increase pain impact when compared to success feedback. Results indicated that repeated failure to control pain increased anger and heart rate responses compared to the other conditions, but not pain intensity. It is concluded that persistent efforts to control pain in the face of failure may lead to the maintenance or exacerbation of physiological and emotional responses.

Negative affect and sensitization to pain

Pain usually has a strong negative affective component, which is believed to modulate pain perception. After reviewing theories on the link between negative affect and pain, mechanisms are discussed by which negative affect may either increase or inhibit pain. Possible pain-inhibiting mechanisms are endogenous opioid release, blood pressure reactivity, and distraction of attention; possible pain-increasing mechanisms are autonomic and muscular reactivity, misattribution of arousal, hypervigilance to pain, worrying, and avoidance behavior. It is emphasized that each of these mechanisms can be very adaptive in acute pain situations to prevent injury and promote recovery. In chronic pain, however, ongoing physiological arousal and hypervigilance to pain, induced or magnified by negative affect, may cause sensitization to pain. Furthermore, worrying about pain and avoidance of pain-inducing activities may increase negative affect, ypervigilance, and functional disability. It is argued that, in the long run, pain-related negative affect has sensitizing and disabling effects.

Experimentally induced anger, cardiovascular reactivity, and pain sensitivity

It was investigated whether an angry state, induced by a computer task with harassing comments, would lead to a decrease in cold pressor pain threshold and tolerance in comparison to a neutral situation. It was hypothesized that an increase in cardiovascular activity might partially mediate effects of anger. Furthermore, it was examined whether subjects given the opportunity to express anger would show reduced cardiovascular activity and pain report compared to subjects not given this opportunity. Finally, trait measures for anger expression style and hostility were included. The results show an increase instead of the expected decrease in pain tolerance for subjects in the harassment condition compared to those in the neutral condition. While cardiovascular reactivity was positively related to pain threshold and tolerance, increased anger was associated with increased pain report. It is suggested that anger and cardiovascular reactivity may have important but sometimes opposing influences on pain.

Real-Life Stress and Opioid-Mediated Analgesia in Novice Parachute Jumpers

Abstract It was investigated whether a stress-induced analgesia could be demonstrated in human subjects (N = 24) performing a first-time parachute jump. Sensitivity for electrical stimulation and pressure pain was measured at several moments before and after the jump. The opioid antagonist naloxone or saline placebo was administered immediately after the jump to examine possible opioid-mediated effects. After the jump, the placebo group showed a lower pain sensitivity than the naloxone group, with the latter returning to pretest levels, consistent with an opioid-mediated analgesia. Although analgesic effects appear to have been initiated prior to the jump, plasma β-endorphin showed a sudden large increase immediately after the jump. This increase correlated with reports of anxiety and loss of control during the jump, and was associated with reduced pain sensitivity. Despite several limitations, this study suggests that the real-life stress of a parachute jump may attenuate pain through endogenous opioid release.

No interactive effects of naltrexone and benzodiazepines on pain during phobic fear

Animal research has shown that anxiety may inhibit pain through the release of endogenous opioids. On the other hand, anxiety is often believed to exacerbate pain in clinical situations, and anxiety reduction has been shown to attenuate the affective component of pain. In the present study phobic anxiety was induced by confronting forty-eight spider phobic subjects with a spider, after which they received two mildly painful electrical stimuli at two different current levels. The benzodiazepine alprazolam (1 mg) was administered to investigate the influence on pain of a reduction in anxiety, while the role of endogenous opioids was studied by administering the opioid antagonist naltrexone (50 mg). Alprazolam resulted in lower anxiety and pain ratings during pain stimulation, supporting the idea that (presumably pain-related) anxiety may increase the experience of pain. Naltrexone did not influence pain and anxiety ratings, nor was there a significant interaction between the two pharmacological manipulations. These findings confirm previous evidence that phobic fear does not necessarily induce an endogenous opioid-mediated analgesia.

Anxiety and pain: epinephrine-induced hyperalgesia and attentional influences

The role of peripheral epinephrine in the influence of anxiety on pain was investigated by intravenously infusing epinephrine and placebo in three increasing doses. The effect of epinephrine was measured within subjects on several subjective and autonomic measures: subjective pain, skin conductance response, heart rate response due to electrical stimulation, threshold for heat pain and threshold for pressure pain. Heat pain threshold was measured both on normal skin and on skin sensitized with capsaicin, since there is evidence that effects of sympathetic stimulation are only to be found in damaged or sensitized skin. Epinephrine caused a slight increase in subjective pain due to electrical stimulation and a decrease in heat pain threshold, which was larger on capsaicin-treated than on normal skin. However, heart rate response due to electrical stimulation and pressure pain threshold were not significantly influenced, while skin conductance response was even inhibited by epinephrine. Attentional focus, which was manipulated within electrical stimulation, seemed to have a much stronger influence on pain responses than pharmacological manipulation, independent of epinephrine. It may be speculated that, although evidence was found for effects of epinephrine on pain, they may be overruled by effects of attention.

No evidence for opioid-mediated analgesia induced by phobic fear

The influence of anxiety on acute pain sensation was investigated, studying the relative contribution of endogenous opioids and attentional mechanisms. Thirty-six spider phobics received mildly painful electrical stimulation, while anxiety and focus of attention were manipulated within subjects. The opioid antagonist naloxone or placebo was administered between subjects to examine an analgesia owing to anxiety-induced endorphinergic activity. In contrast to earlier findings, attention towards pain failed to increase pain as opposed to distraction from pain, probably owing to a less effective attention manipulation. Furthermore, despite high levels of anxiety, subjective pain ratings were not influenced by anxiety, although heart rate responses were slightly inhibited. Accordingly, there was no increase in subjective or physiological pain responses as a result of naloxone, nor did beta-endorphin plasma levels rise during anxiety. The results suggest that phobic anxiety does not induce an opioid-mediated analgesia. Curiously, naloxone itself effected a dose-dependent analgesia compared to placebo during both high and low anxiety, which is compatible with the assumption of agonist properties of naloxone in the absence of opioid activity.

Anxiety and pain: attentional and endorphinergic influences

The role of attentional mechanisms and endogenous opioids in the influence of anxiety on acute pain sensation was investigated. Forty-five spider phobics received mildly painful electrical stimulation. The opioid antagonist naltrexone or placebo was administered between subjects to examine an analgesia due to anxiety-induced endorphinergic activity, while anxiety and focus of attention were manipulated within subjects. In accordance with previous research, pain ratings and skin conductance responses (SCRs) were not influenced by anxiety when focus of attention was controlled for. Attention towards pain led to an increase in subjective pain as opposed to distraction from pain. SCRs, however, were increased in the distraction conditions, probably due to heightened unexpectedness. Further, both high and low anxiety resulted in an analgesia compared to the pretest in the placebo condition, which was reversed by a low dose of naltrexone, but not by a high dose. Apart from possible agonist properties of high doses of naltrexone, this effect suggests an opioid-induced analgesia. It remains to be demonstrated whether this was due to endogenous opioids released during high anxiety.

Effect of glutamate stimulation of bed nucleus of the stria terminalis on arterial pressure and heart rate

Experiments were done in the chloralose-anesthetized, paralyzed, and artificially ventilated rat to determine the cardiovascular responses elicited during chemical stimulation of bed nucleus of the stria terminalis (BST) and to investigate the components of the peripheral autonomic nervous system that mediate these responses. Neurons in BST were selectively stimulated by the microinjection (10-20 nl) of the excitatory amino acid L-glutamate (1 M). Stimulation of BST elicited decreases in mean arterial pressure (n = 105) of -6 to -55 mmHg. These depressor responses were on occasion (n = 60) accompanied by decreases in heart rate ranging between -10 and -40 beats/min. The largest depressor responses were consistently elicited from a crescent-shaped region of BST around the dorsolateral, lateral, and ventrolateral surfaces of the anterior commissure. Intravenous administration of the muscarinic receptor blocker, atropine methylbromide, had no affect on the magnitude of the mean arterial pressure and heart rate responses. On the other hand, administration (intravenous) of the nicotinic receptor blocker, hexamethonium bromide or arfonad, abolished both the depressor response and cardiac slowing during stimulation of BST. These data suggest that the BST depressor and the bradycardia responses are mediated by inhibition of both sympathetic vasoconstrictor fibers to the vasculature and cardioacceleratory fibers to the heart, respectively.