Power In Low Frequency Band Research Articles

Relationship Between Endothelial Function, Vital Parameters, and Cognitive Performance in Community Dwellers with Subjective Cognitive Decline: An Observational Study with Six Months Follow Up.

With advancing age, cognitive decline is frequently associated with endothelial dysfunction, but data on vascular performance prior to the onset of mild cognitive impairment (MCI) is scarce. To investigate the relationship between endothelial function, vital parameters and cognitive performance in older adults with subjective cognitive decline (SCD). Forty-five volunteers aged 65 years and older with SCD underwent comprehensive geriatric assessment-based prognosis evaluation by means of the Multidimensional Prognostic Index (MPI), full neuropsychological examination and peripheral arterial tonometry measurement by means of EndoPAT™2000 to evaluate endothelial flexibility and vital parameters. Six months after initial evaluation, participants were contacted by phone and a telephone-administered version of the MPI (TELE-MPI) was conducted. Fifteen study participants scored below the cutoff score of 26 on the Montreal Cognitive Assessment, suggesting MCI (26.56±2.23). Nominal significant correlations were found between heart rate (HR) and trail making test (TMT) A (β= -0.49, p = 0.03), between heart rate variability (HRV) and TMT B (β= 0.78, p = 0.041), between power of low-frequency band (LF) HRV and Mini Nutritional Assessment-Short Form (β= 0.007, p = 0.037) as well as between augmentation index (AI) and CogState Detection Test (β= 0.002, p = 0.034). HR, HRV, and AI, but not endothelial flexibility are associated with cognitive performance in SCD and suspected MCI patients and may serve as clinical biomarkers in the early diagnosis of neurodegenerative disorders with advancing age.

Influence of shift work on sleep quality and circadian patterns of heart rate variability among nurses.

Shift work implementation is essential for providing continuous patient care in hospitals. However, working in shifts on a routine basis may disrupt the circadian pattern and alter the sleep-wakefulness cycle in nurses. Stress due to shift work can influence the adaptability of the cardiovascular system, produce psychophysiological strain and deteriorate work performance in female nurses. This study investigated the effect of morning and night shift work on sleep quality and circadian patterns governing heart rate variability (HRV) in female nurses working in a tertiary care hospital. Thirty-eight healthy female nurses were recruited. Frequency and time domain parameters of HRV were recorded as markers of cardiac autonomic function. A student t-test was used to investigate differences in HRV between morning and night shift workers. Mann-Whitney non-parametric test was applied for the difference between Pittsburgh Sleep Quality Index (PSQI) scores in the two groups. Standard deviation of the normal-to-normal interval (SDNN) (msec), total power (ms2) and high-frequency (HF) band power (ms2) were significantly reduced in night shift nurses than in morning shift nurses. The low-frequency (LF)/HF ratio was significantly increased in night shift nurses. The differences in standard deviation of the averages of NN intervals (SDaNN) (msec), root mean square of successive differences between adjacent NN intervals (RMSSD), mean NN, very low-frequency (VLF) band power (ms2) and LF band power (ms2) were not statistically significant. The global PSQI score was significantly higher among night shift workers than in morning shifts. Inadequate sleep can disrupt the body's ability to regulate heart rhythm and increase the risk of cardiovascular diseases and mortality. The research suggests a propensity for autonomic imbalance in night shift workers when compared to their counterparts on morning shifts.

Effects of Exercise Training on Heart Rate Variability in Healthy Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

This meta-analysis was conducted to investigate the effects of exercise training on heart rate variability (HRV) parameters associated with the autonomic nervous system (ANS) activity. Randomized controlled trials (RCTs) involving healthy adults (aged ≥ 18 years) were included. We searched PubMed, Scopus, Web of Science, and EBSCO databases to identify relevant studies. A random-effects meta-analysis was performed using the standardized mean difference (SMD) and 95% confidence interval (CI). Sixteen RCTs with a total of 623participants were selected for the final analysis. The analysis showed that exercise training improved the standard deviation of normal-to-normal intervals (SDNN) (SMD: 0.58 (0.16, 1.00); p = 0.007), the root mean square of successive differences in heart period series (RMSSD) (SMD: 0.84 (0.36, 1.31); p = 0.0005), and the absolute power of high-frequency band (HF) (SMD: 0.89 (0.27, 1.51); p = 0.005) parameters compared to the control group. Analysis of the moderator variables showed that the effect of exercise on HRV indices may be influenced by sex, age, and type of exercise used, specifically in HF band, absolute power of low-frequency band (LF), and LF/HF ratio parameters. Despite the limited number of existing RCTs related to the subject, the results suggest that exercise training enhances HRV parameters associated with vagal-related activity (RMSSD and HF) and both sympathetic and parasympathetic activities (SDNN). This study overcomes the lack of meta-analyses on the effects of exercise training on autonomic modulation among healthy adults and may bridge the gap in understanding the potential physiological underpinnings of the acknowledged positive health benefits of exercise.

Artificial light at night affects the daily profile of pulse pressure and protein expression in the thoracic aorta of rats

Artificial light at night (ALAN) disrupts 24-h variability of blood pressure, but the molecular mechanisms underlying these effects are unknown. Therefore, we analysed the daily variability of pulse pressure, the maximum value of acceleration rate of aortic pressure (dP/dt(max)) measured by telemetry and protein expression in the thoracic aorta of normotensive male rats exposed to ALAN (1–2 lx) for 3 weeks. Daily, 24-h variability of pulse pressure and dP/dt(max) was observed during a regular light/dark regimen with higher values during the dark compared to the light phase of the day. ALAN suppressed 24-h variability and enhanced ultradian (<12-h) periods of pulse pressure and dP/dt(max) in duration-dependent manners. From beat-to-beat blood pressure variability, ALAN decreased low-frequency bands (a sympathetic marker) and had minimal effects on high-frequency bands. At the molecular level, ALAN decreased angiotensin II receptor type 1 expression and reduced 24-h variability. ALAN caused the appearance of 12-h oscillations in transforming growth factor β1 and fibulin 4. Expression of sarco/endoplasmic reticulum Ca2+-ATPase type 2 was increased in the middle of the light and dark phase of the day, and ALAN did not affect its daily and 12-h variability. In conclusion, ALAN suppressed 24-h variability of pulse pressure and dP/dt(max), decreased the power of low-frequency bands and differentially affected the expression of specific proteins in the rat thoracic aorta. Suppressed 24-h oscillations by ALAN underline the pulsatility of individual endocrine axes with different periods, disrupting the cardiovascular control of central blood pressure.

The Influence of Autonomic Nervous System during Resting State on the Peripheral Pulse Wave Velocity in Young Adult Males

Abstract Background: The association between the activity of autonomic nervous systems (ANS) and pulse wave velocity (PWV) was commonly deduced after adjusting for confounding factors. The relationship between the ANS and PWV was either maintained, but attenuated, or no longer statistically connected after controlling for confounding variables. Research in young healthy individuals showed that the ANS does not control aortic stiffness (indexed by PWV) in a pressure-independent manner. Therefore, the role of the ANS in controlling PWV is debatable. Objectives: The objective of this study was to examine the possibility that ANS directly affects PWV independent of blood pressure (BP) and heart rate (HR). Subjects and Methods: Thirty-four healthy male volunteers (19 years old) were recruited. Stable brachial systolic BP (SBP)/diastolic BP (DBP) and HR were measured in semi-supine position after a 15-min rest. During the last 5 min, fingertip digital pulse wave (DPW) and lead II electrocardiogram (ECG) signals were recorded. The pulse transit time, and consequently PWV, was calculated by measuring the duration between the ECG R wave climax and a reference point on the DPW in the same cardiac cycle. The ANS activity was assessed by calculating the HR variability (HRV) indices obtained from the ECG record of 5-min R-R intervals (RRIs). Results: HRV indices low-frequency (LF)/high-frequency (HF) (LF band power measured in the 0.04–0.15 Hz)/the HF band power measured in the 0.15–0.4 Hz band) and SD2/SD1 ratios (SD1 and SD2 represent the dispersion along the minor and major axis of the fitted ellipse of the Poincaré plot) (sympathovagal balance) were significantly and positively correlated with PWV. In addition, the standard deviation of RRI, or normal-to-normal “NN” (SDNN) interval, after excluding ectopic beats, the square root of the mean squared differences of successive NN intervals (RMSSD) were significantly and negatively correlated with the PWV. No correlation was obtained between PWV and HR, SBP, or DBP. Conclusion: Peripheral PWV during rest or inactivity is affected directly by the sympathovagal balance independent of BP.

Acute Effect of Positive Airway Pressure on Heart Rate Variability in Obstructive Sleep Apnea.

Autonomic dysregulation is associated with cardiovascular consequences in obstructive sleep apnea (OSA). This study aimed to investigate the effect of acute continuous positive airway pressure (CPAP) treatment on autonomic activity and to identify factors contributing to heart rate variability (HRV) changes in OSA. Frequency domain HRV parameters were calculated and compared between the baseline polysomnography and during the CPAP titration in 402 patients with moderate to severe OSA. There were significant reductions in total power, very low-frequency band power, low-frequency band power, and high-frequency band power during the CPAP titration as compared to the baseline polysomnography. This tendency was pronounced in male patients with severe OSA. Multivariate analysis found that changes in the apnea-hypopnea index and oxygen saturation were significantly associated with changes in sympathetic and parasympathetic activity, respectively. This study demonstrated that HRV parameters significantly changed during the CPAP titration, indicating a beneficial effect of CPAP in the restoration of sympathetic and parasympathetic hyperactivity in OSA. Prospective longitudinal studies should determine whether long-term CPAP treatment aids in maintaining the long-lasting improvement of the autonomic functions, thereby contributing to the prevention of cardiovascular and cerebrovascular diseases in patients with OSA.

O010 Capturing Localised Electroencephalography Signals During Sleep using Tripolar Concentric Ring Electrodes

Abstract Introduction Tri -concentric ring electrodes (TCRE) evaluate the current density underlying each electrode and provide improved signal-to-noise compared to conventional electroencephalography (EEG) electrodes. This pilot study used TCRE for the first time to compare TCRE versus more conventional EEG signals during sleep . Materials and Method Twenty healthy sleepers (8 males, mean±SD age 27.8±9.6 y) completed a 9-hr sleep opportunity. Eighteen TCRE electrodes were placed based on the 10-20 system, along with more conventional EEG recorded from the outer rings of paired TCRE electrodes (emulated EEG; eEEG). A Fast Fourier Transform using multitaper-based estimation was applied in 5 second epochs to calculate absolute and relative powers in delta, alpha, theta, sigma and beta frequency bands for eEEG and TCRE signals throughout conventionally scored sleep stages. Results At the Cz position, TCRE showed reduced relative powers in beta frequency bands across sleep stages compared to eEEG. Further, TCRE demonstrated lower relative beta activity during wake (mean difference [95% confidence lower, upper]; -14%, [-15.9%, -12.1%]), N1 sleep (-5.7%, [-7.6%, -3.7%]), and REM sleep (-4.4%, [-6.3%, -2.5%]). TCRE also recorded higher relative delta power across all stages of sleep and wake. Conclusions Lower signal power in high frequency bands and higher power in lower frequency bands supports more favourable signal-to-noise ratio with TCRE compared to more conventional EEG. Thus, TCRE shows promise for evaluating sleep related brain activity. The more focal nature of TCRE recordings may be an additional advantage, that warrants further analysis.

Evaluation of cardiovascular autonomic dysfunction in symptomatic post-COVID-19 patients using the heart rate variability (HRV) and detection of subtle LV dysfunction using 2D global longitudinal strain (GLS)

AimThe COVID-19 disease primarily affects the respiratory system; however, cardiac involvement has been documented in the acute phase. We aimed to evaluate the cardiac autonomic function and subtle left ventricular dysfunction in those subjects recovered from mild to moderate acute COVID-19 patients but still symptomatic.Methods and resultsThe study group was composed of 50 subjects with confirmed mild to moderate COVID-19. All subjects underwent routine 2D echocardiography assessment in addition to 2D speckle tracking and 24 h Holter monitoring for HRV analysis. The mean age of the study population was 42 ± 18 years; symptoms were reported as follows 27 (54%) had dyspnoea, 17 (34%) had palpitation, and 7 (14%) had dizziness. Time domain parameters Standard Deviation of NN intervals (SDNN), Standard Deviation of the Average NN intervals for each 5 min segment of a 24 h HRV recording (SDANN), and Root Mean Square of Successive RR interval Differences (rMSSD) were diminished with mean SDNN value being markedly impaired in 12 (24%) patients, while frequency domain parameters as assessed by the ratio of the Low-Frequency band power to the High-Frequency band power (LF/HF) with the mean of 1.837 with 8% of the patients being impaired. SDNN was significantly reduced in patients with impaired global longitudinal strain (p 0.000). The global longitudinal strain was diminished in 10 patients (20%); also, 80% of the patients with impaired GLS had decreased SDNN.ConclusionOur study targeted patients experiencing prolonged symptoms after COVID-19 illness. We detected a high incidence of GLS impairment using Speckle Tracking Echocardiography (STE) and a significant prevalence of diminished HRV. HRV (especially SDNN) and GLS were found to be significantly correlated.Graphical abstract

Neurophysiological MEG markers of cognitive impairment and performance validity in multiple sclerosis

Background: Suboptimal performance during neuropsychological testing frequently occurs in multiple sclerosis (MS), leading to unreliable cognitive outcomes. Neurophysiological alterations correlate with MS-related cognitive impairment, but studies have not yet considered performance validity. Objectives: To investigate neurophysiological markers of cognitive impairment in MS, while explicitly addressing performance validity. Methods: Magnetoencephalography recordings, neuropsychological assessments, and performance validity testing were obtained from 90 MS outpatients with cognitive complaints. Spectral and resting-state functional connectivity (rsFC) properties were compared between cognitively impaired (CI), cognitively preserved (CP), and suboptimally performing (SUB) patients using regression models and permutation testing. Results: CI had higher power in low-frequency bands and lower power in high bands compared to CP, indicating neuronal slowing. CI also showed lower beta power compared to SUB. Overall power spectra visually differed between CI and CP, and SUB showed overlap with both groups. CI had lower rsFC than CP and SUB patients. CP and SUB patients showed no differences. Conclusion: Neuronal slowing and altered rsFC can be considered cognitive markers in MS. Patients who performed suboptimally showed resemblance with patients with and without cognitive impairments, and although their overall neurophysiological profile was more similar to patients without impairments, it suggests heterogeneity regarding their pathophysiology.

Heart rate variability and microvolt Twave alternans changes during ajmaline test may predict prognosis in Brugada syndrome.

Drug-induced typeI Brugada syndrome (BrS) is associated with a ventricular arrhythmia (VA) rate of 1 case per 100 person-years. This study aims to evaluate changes in electrocardiographic (ECG) parameters such as microvolt Twave alternans (mTWA) and heart rate variability (HRV) at baseline and during ajmaline testing for BrS diagnosis. Consecutive patients diagnosed with BrS during ajmaline testing with 5-year follow-up were included in this study. For comparison, a negative ajmaline control group and an isoproterenol control group were also included. ECG recordings during ajmaline or isoproterenol test were divided in two timeframes from which ECG parameters were calculated: a 5-min baseline timeframe and a 5-min drug timeframe. A total of 308 patients with BrS were included, 22 (0.7%) of which suffered VAs during follow-up. One hundred patients were included in both isoproterenol and negative ajmaline control groups. At baseline, there was no difference in ECG parameters between control groups and patients with BrS, nor between BrS with and without VAs. During ajmaline testing, BrS with VAs presented longer QRS duration [159 ± 34ms versus 138 (122-155) ms, p = 0.006], higher maximum mTWA [33.8 (14.0-114) µV versus 8.00 (3.67-28.2)µV, p = 0.001], and lower power in low frequency band [25.6 (5.8-53.8) ms2 versus 129.5 (52.7-286) ms2, p < 0.0001] when compared to BrS without VAs. Ajmaline induced important HRV changes similar to those observed during isoproterenol. Increased mTWA was observed only in patients with BrS. BrS with VAs during follow-up presented worse changes during ajmaline test, including lower LF power and higher maximum mTWA which were independent predictors of events.

Habituation of the stress response multiplex to repeated cold pressor exposure.

Humans show remarkable habituation to aversive events as reflected by changes of both subjective report and objective measures of stress. Although much experimental human research focuses on the effects of stress, relatively little is known about the cascade of physiological and neural responses that contribute to stress habituation. The cold pressor test (CPT) is a common method for inducing acute stress in human participants in the laboratory; however, there are gaps in our understanding of the global state changes resulting from this stress-induction technique and how these responses change over multiple exposures. Here, we measure the stress response to repeated CPT exposures using an extensive suite of physiologic measures and state-of-the-art analysis techniques. In two separate sessions on different days, participants underwent five 90 s CPT exposures of both feet and five warm water control exposures, while electrocardiography (ECG), impedance cardiography, continuous blood pressure, pupillometry, scalp electroencephalography (EEG), salivary cortisol and self-reported pain assessments were recorded. A diverse array of adaptive responses are reported that vary in their temporal dynamics within each exposure as well as habituation across repeated exposures. During cold-water exposure there was a cascade of changes across several cardiovascular measures (elevated heart rate (HR), cardiac output (CO) and Mean Arterial Pressure (MAP) and reduced left ventricular ejection time (LVET), stroke volume (SV) and high-frequency heart rate variability (HF)). Increased pupil dilation was observed, as was increased power in low-frequency bands (delta and theta) across frontal EEG electrode sites. Several cardiovascular measures also habituated over repeated cold-water exposures (HR, MAP, CO, SV, LVET) as did pupil dilation and alpha frequency activity across the scalp. Anticipation of cold water induced stress effects in the time-period immediately prior to exposure, indexed by increased pupil size and cortical disinhibition in the alpha and beta frequency bands across central scalp sites. These results provide comprehensive insight into the evolution of a diverse array of stress responses to an acute noxious stressor, and how these responses adaptively contribute to stress habituation.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ВЕГЕТАТИВНОЙ НЕРВНОЙ СИСТЕМЫ ПОДРОСТКОВ С РАЗНОЙ СТЕПЕНЬЮ ВОВЛЕЧЕННОСТИ В ЦИФРОВУЮ СРЕДУ

The modern literature records a high relevance of diagnosing the deterioration of the psychological health of the younger generation in conditions of accelerated digitalization, determined by psycho-emotional stress and is associated with the functions of the autonomic nervous system (ANS), the role of which has not been studied either in the formation of over-involvement with the Internet, or in determining the success of the development of educational programs by modern youth. One of the most important markers for assessing the activity of the ANS is the heart rate and its variability. Thus, the purpose of our work can be defined as the study of the relationship of heart rate parameters (R-R intervals) with the characteristics of digital preferences of adolescents. It is assumed that the choice of activities on the Internet, as well as the time spent on leisure, have certain connections with the characteristics of R-R intervals and its variability, with the predominance of activity of the parasympathetic or sympathetic links of the ANS. The study was carried out during the COVID-19 pandemic in 2021, which aggravated the psycho-emotional state of students. The author’s questionnaire “Digital preferences of modern teenagers” was used in the work, which had previously been tested on schoolchildren in Moscow. In a separate experiment on a part of the total sample of students (n = 24), a R-R intervals was recorded using a certified ECG device of the APK “Veda-pulse”. Registration was carried out individually with each subject, on average, ECG registration lasted 5 minutes. The characteristics of the behavior of the surveyed group of St. Petersburg schoolchildren have a high degree of similarity with all other surveyed groups of peers in Moscow and Lipetsk. The frequency-spectral parameters of the R-R- interval’s variability in a separate experiment are characterized by high variety, the maximum group variety is shown for the low frequency band (LF) of the spectrum of R-R intervals. A highly reliable positive relationship of priority interests on the Internet with the power of the spectrum of all frequency bands and with the gender of the subjects was found. Students' academic performance correlates positively and with highly reliably with the power of the super low frequency band (VLF) and negatively with the power of the low frequency band (LF). The results are discussed in the context of the interrelationships of students' academic performance, gender and interests on the Internet with the activity of their sympathetic and parasympathetic components of the ANS and the central link of heart rate regulation.

Obstructive sleep apnoea-related respiratory events and desaturation severity are associated with the cardiac response.

BackgroundObstructive sleep apnoea (OSA) causes, among other things, intermittent blood oxygen desaturations, increasing the sympathetic tone. Yet the effect of desaturations on heart rate variability (HRV), a simple and noninvasive method for assessing sympathovagal balance, has not been comprehensively studied. We aimed to study whether desaturation severity affects the immediate HRV.MethodsWe retrospectively analysed the electrocardiography signals in 5-min segments (n=39 132) recorded during clinical polysomnographies of 642 patients with suspected OSA. HRV parameters were calculated for each segment. The segments were pooled into severity groups based on the desaturation severity (i.e. the integrated area under the blood oxygen saturation curve) and the respiratory event rate within the segment. Covariate-adjusted regression analyses were performed to investigate possible confounding effects.ResultsWith increasing respiratory event rate, the normalised high-frequency band power (HFNU) decreased from 0.517 to 0.364 (p<0.01), the normalised low-frequency band power (LFNU) increased from 0.483 to 0.636 (p<0.01) and the mean RR interval decreased from 915 to 869 ms (p<0.01). Similarly, with increasing desaturation severity, the HFNU decreased from 0.499 to 0.364 (p<0.01), the LFNU increased from 0.501 to 0.636 (p<0.01) and the mean RR interval decreased from 952 to 854 ms (p<0.01). Desaturation severity-related findings were confirmed by considering the confounding factors in the regression analyses.ConclusionThe short-term HRV response differs based on the desaturation severity and the respiratory event rate in patients with suspected OSA. Therefore, a more detailed analysis of HRV and desaturation characteristics could enhance OSA severity estimation.

Psilocybin reduces low frequency oscillatory power and neuronal phase-locking in the anterior cingulate cortex of awake rodents

Psilocybin is a hallucinogenic compound that is showing promise in the ability to treat neurological conditions such as depression and post-traumatic stress disorder. There have been several investigations into the neural correlates of psilocybin administration using non-invasive methods, however, there has yet to be an invasive study of the mechanism of action in awake rodents. Using multi-unit extracellular recordings, we recorded local field potential and spiking activity from populations of neurons in the anterior cingulate cortex of awake mice during the administration of psilocybin (2 mg/kg). The power of low frequency bands in the local field potential was found to significantly decrease in response to psilocybin administration, whilst gamma band activity trended towards an increase. The population firing rate was found to increase overall, with just under half of individual neurons showing a significant increase. Psilocybin significantly decreased the level of phase modulation of cells with each neural frequency band except high-gamma oscillations, consistent with a desynchronization of cortical populations. Furthermore, bursting behavior was altered in a subset of cells, with both positive and negative changes in the rate of bursting. Neurons that increased their burst firing following psilocybin administration were highly likely to transition from a phase-modulated to a phase unmodulated state. Taken together, psilocybin reduces low frequency oscillatory power, increases overall firing rates and desynchronizes local neural activity. These findings are consistent with dissolution of the default mode network under psilocybin, and may be indicative of disruption of top-down processing in the acute psychedelic state.

Comparing Ictal Cardiac Autonomic Changes in Patients with Frontal Lobe Epilepsy and Temporal Lobe Epilepsy by Ultra-Short-Term Heart Rate Variability Analysis.

Background and Objectives: Abnormal epileptic discharges in the brain can affect the central brain regions that regulate autonomic activity and produce cardiac symptoms, either at onset or during propagation of a seizure. These autonomic alterations are related to cardiorespiratory disturbances, such as sudden unexpected death in epilepsy. This study aims to investigate the differences in cardiac autonomic function between patients with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE) using ultra-short-term heart rate variability (HRV) analysis around seizures. Materials and Methods: We analyzed electrocardiogram (ECG) data recorded during 309 seizures in 58 patients with epilepsy. Twelve patients with FLE and 46 patients with TLE were included in this study. We extracted the HRV parameters from the ECG signal before, during and after the ictal interval with ultra-short-term HRV analysis. We statistically compared the HRV parameters using an independent t-test in each interval to compare the differences between groups, and repeated measures analysis of variance was used to test the group differences in longitudinal changes in the HRV parameters. We performed the Tukey–Kramer multiple comparisons procedure as the post hoc test. Results: Among the HRV parameters, the mean interval between heartbeats (RRi), normalized low-frequency band power (LF) and LF/HF ratio were statistically different between the interval and epilepsy types in the t-test. Repeated measures ANOVA showed that the mean RRi and RMSSD were significantly different by epilepsy type, and the normalized LF and LF/HF ratio significantly interacted with the epilepsy type and interval. Conclusions: During the pre-ictal interval, TLE patients showed an elevation in sympathetic activity, while the FLE patients showed an apparent increase and decrease in sympathetic activity when entering and ending the ictal period, respectively. The TLE patients showed a maintained elevation of sympathetic and vagal activity in the pos-ictal interval. These differences in autonomic cardiac characteristics between FLE and TLE might be relevant to the ictal symptoms which eventually result in SUDEP.

Acute Effect of Kapalbhati Yoga on Cardiac Autonomic Control Using Heart Rate Variability Analysis in Healthy Male Individuals

Kapalbhati is well known for improving cardiovascular health. But there are some reports of heart attacks while practising kapalbhati. We hypothesize that ill-effect of kapalbhati could be because of autonomic dysfunction to heart. In the present study, we aim to understand the acute effect of kapalbhati yoga on heart rate dynamics using heart rate variability (HRV) analysis. Resting heart rate (HR) varies widely in different individuals and during various physiological stresses, particularly, exercise it can go up to three-fold. These changes in heart rate are known as heart rate variability (HRV). Variability in heart rate reflects the control of autonomic system on the heart and which can be determined during brief periods of electrocardiographic (ECG) monitoring. HRV measures the effect of any physical exercise on the heart rate using time- and frequency-domain methods. Frequency-domain method involves power spectral analyses of the beat-to-beat intervals (R-R intervals) variability data. When total power vs. frequency, fast fourier transform analysis of R-R intervals data is done, it shows three well-defined peaks/rhythms in every individual, which contain different physiological information. Thus, the total spectral power of R-R intervals data can be divided into three components or bands viz., the very low frequency (VLF) band, the low-frequency (LF) band and the high frequency (HF) band. VLF represent very long time-period physiological phenomenon like thermoregulation, circadian rhythms etc. and thus are not seen in short-term recordings like in this work. LF band power represents long period physiological rhythms in the frequency range of 0.05- 0.15 Hz and LF band power increases as a consequence of sympathetic activation. HF band represent physiological rhythms in the frequency range of 0.15-0.5 Hz and they are synchronous with the respiration rate, and arise due to the intrathoracic pressure changes and mechanical vibrations caused by the breathing activity. In this work, twenty healthy male volunteers were trained in kapalbhati yoga and their ECG waveforms (2 min.) were obtained while doing kapalbhati (breathing at 1 Hz frequency for 2 min.) and were compared with the baseline (just 2 min. before the start) and post-kapalbhati (immediately 2 min. after completing the practice) HRV data. Our results showed a significant decrease in the time-domain measures i.e., NN50, pNN50 and the mean heart rate interval during-kapalbhati when compared statistically to the respective before practice or “pre”-kapalbhati (p &lt; 0.05, student’s paired t-test) values. Frequency-domain indices showed that during-kapalbhati there is a significant increase (~48%) in the LF band power which suggests sympathetic activation and a significant increase (~88%) in the low frequency to the high frequency power ratio (LF/HF ratio) which indicates sympathetic system predominance. A significant decrease (~63%) in the HF component was also noted during-kapalbhati as compared to the “pre-kapalbhati” values which shows decrease in parasympathetic tone. Thus, these results suggest that during-kapalbhati there is drastic increase of sympathetic tone whereas parasympathetic activity is reduced. We propose these changes in autonomic system control on heart are responsible for the myocardial ischemic attacks induced during kapalbhati in some individuals.

Source-level Cortical Power Changes for Xenon and Nitrous Oxide-induced Reductions in Consciousness in Healthy Male Volunteers.

Investigations of the electrophysiology of gaseous anesthetics xenon and nitrous oxide are limited revealing inconsistent frequency-dependent alterations in spectral power and functional connectivity. Here, the authors describe the effects of sedative, equivalent, stepwise levels of xenon and nitrous oxide administration on oscillatory source power using a crossover design to investigate shared and disparate mechanisms of gaseous xenon and nitrous oxide anesthesia. Twenty-one healthy males underwent simultaneous magnetoencephalography and electroencephalography recordings. In separate sessions, sedative, equivalent subanesthetic doses of gaseous anesthetic agents nitrous oxide and xenon (0.25, 0.50, and 0.75 equivalent minimum alveolar concentration-awake [MACawake]) and 1.30 MACawake xenon (for loss of responsiveness) were administered. Source power in various frequency bands were computed and statistically assessed relative to a conscious/pre-gas baseline. Observed changes in spectral-band power (P < 0.005) were found to depend not only on the gas delivered, but also on the recording modality. While xenon was found to increase low-frequency band power only at loss of responsiveness in both source-reconstructed magnetoencephalographic (delta, 208.3%, 95% CI [135.7, 281.0%]; theta, 107.4%, 95% CI [63.5, 151.4%]) and electroencephalographic recordings (delta, 260.3%, 95% CI [225.7, 294.9%]; theta, 116.3%, 95% CI [72.6, 160.0%]), nitrous oxide only produced significant magnetoencephalographic high-frequency band increases (low gamma, 46.3%, 95% CI [34.6, 57.9%]; high gamma, 45.7%, 95% CI [34.5, 56.8%]). Nitrous oxide-not xenon-produced consistent topologic (frontal) magnetoencephalographic reductions in alpha power at 0.75 MACawake doses (44.4%; 95% CI [-50.1, -38.6%]), whereas electroencephalographically nitrous oxide produced maximal reductions in alpha power at submaximal levels (0.50 MACawake, -44.0%; 95% CI [-48.1,-40.0%]). Electromagnetic source-level imaging revealed widespread power changes in xenon and nitrous oxide anesthesia, but failed to reveal clear universal features of action for these two gaseous anesthetics. Magnetoencephalographic and electroencephalographic power changes showed notable differences which will need to be taken into account to ensure the accurate monitoring of brain state during anaesthesia.

Gamma Power during Working Memory in Pre‐symptomatic Alzheimer’s Disease Differs from Normal Healthy Aging

Background and ObjectivesGamma power reduction has been reported in Alzheimer’s disease (AD), and gamma stimulation helps remove amyloid/tau in a preclinical AD model. We hypothesized that gamma power during N‐back working memory testing in pre‐symptomatic AD individuals is lower than in healthy aging, and that gamma power will correlate with n‐back performance.MethodsBrain gamma power from elderly study participants were measured during working memory testing with different workload: participants were presented a series of letters and asked to identify letter ‘X’ (0‐back, low workload) or to identify the letter that same as shown 2 letters ago (2‐back, high workload). Participants consisted of two subgroups from cerebrospinal fluid proteins: cognitively healthy with normal CSF amyloid/tau ratio (CH‐NAT, n=10) or pathological CSF amyloid/tau ratio (CH‐PAT, or pre‐symptomatic AD, n=14) between 63–94 years of age. We compared gamma power, including low gamma band (30–50Hz) and high gamma band (50–80Hz) between two CH groups from electroencephalogram (EEG) at six brain regions including frontal (F); central (C), parietal (P), left temporal (LT), right temporal (RT), and occipital (O) regions. Preprocessing steps included epoching, filtering, re‐referencing, large artifact removal, and time‐frequency analysis. We used simple student two‐sided t‐test to compare gamma power between two groups, and Pearson's linear correlation for the relationship between gamma power and behavioral performance (accuracy (ACC) and response time (RT)). Since this was an exploratory study, a significance level of 0.05 was used for all tests.Results &amp; DiscussionDuring 0‐back compared to CH‐NATs, low gamma in CH‐PATs is higher over F,C regions (p=0.014~0.032). However during 2‐back, low gamma in CH‐PATs is lower over T3,T4 sensors (p=0.044 and 0.028, respectively), and high gamma is lower in P region (p=0.035), compared to CH‐NATs. In addition, only in CH‐NATs low gamma during 2‐back is positively correlated with 0‐back accuracy over F,C,P,LT,RT regions (p=0.0098~0.027, r=0.69~0.77); high gamma during 2‐back is positively correlated with 0‐back accuracy over all regions (p=0.007~0.030, r=0.68~0.78). High gamma during 2‐back is negatively correlated with 0‐back response time over P,RT,O regions (p=0.025~0.037, r=−0.70~−0.66). These results suggest that gamma is compromised in the pre‐symptomatic AD stage. The correlations of gamma with 0‐back accuracy in CH‐NATs but not CH‐PATs indicate gamma played a critical part of performing working memory test (most significantly in the frontal region); we interpret this as diminished capability to hold the testing goal with all other regions involved in CH‐PATs compared to CH‐NATs. Our study further supports a compromised frontal function in pre‐symptomatic AD. The results also support further study of the relationship between gamma and low frequency band power (such as alpha and theta) in pre‐symptomatic AD.Support or Funding InformationAcknowledgmentFinancial support provided by the L.K.Whittier Foundation, NIH R56 Funding 1R56AG063857‐01. Betty Chung and David Buennagel assisted with patient recruitment.

Electroencephalographic spectral power as a marker of cortical function and disease severity in girls with Rett syndrome

BackgroundRett syndrome is a neurodevelopmental disorder caused by a mutation in the X-linked MECP2 gene. Individuals with Rett syndrome typically develop normally until around 18 months of age before undergoing a developmental regression, and the disorder can lead to cognitive, motor, sensory, and autonomic dysfunction. Understanding the mechanism of developmental regression represents a unique challenge when viewed through a neuroscience lens. Are circuits that were previously established erased, and are new ones built to supplant old ones? One way to examine circuit-level changes is with the use of electroencephalography (EEG). Previous studies of the EEG in individuals with Rett syndrome have focused on morphological characteristics, but few have explored spectral power, including power as an index of brain function or disease severity. This study sought to determine if EEG power differs in girls with Rett syndrome and typically developing girls and among girls with Rett syndrome based on various clinical characteristics in order to better understand neural connectivity and cortical organization in individuals with this disorder.MethodsResting state EEG data were acquired from girls with Rett syndrome (n = 57) and typically developing children without Rett syndrome (n = 37). Clinical data were also collected for girls with Rett syndrome. EEG power across several brain regions in numerous frequency bands was then compared between girls with Rett syndrome and typically developing children and power in girls with Rett syndrome was compared based on these clinical measures. 1/ƒ slope was also compared between groups.ResultsGirls with Rett syndrome demonstrate significantly lower power in the middle frequency bands across multiple brain regions. Additionally, girls with Rett syndrome that are postregression demonstrate significantly higher power in the lower frequency delta and theta bands and a significantly more negative slope of the power spectrum. Increased power in these bands, as well as a more negative 1/ƒ slope, trended with lower cognitive assessment scores.ConclusionsIncreased power in lower frequency bands is consistent with previous studies demonstrating a “slowing” of the background EEG in Rett syndrome. This increase, particularly in the delta band, could represent abnormal cortical inhibition due to dysfunctional GABAergic signaling and could potentially be used as a marker of severity due to associations with more severe Rett syndrome phenotypes.

Low-frequency ventilatory oscillations in hypoxia are a major contributor to the low-frequency component of heart rate variability

Heart rate variability (HRV) may be influenced by several factors, such as environment (hypoxia, hyperoxia, hypercapnia) or physiological demand (exercise). In this retrospective study, we tested the hypothesis that inter-beat (RR) intervals in healthy subjects exercising under various environmental stresses exhibit oscillations at the same frequency than ventilatory oscillations. Spectra from RR intervals and ventilation ([Formula: see text]E) were collected from 37 healthy young male subjects who participated in 5 previous studies focused on ventilatory oscillations (or periodic breathing) during exercise in hypoxia, hyperoxia and hypercapnia. Bland and Altman test and multivariate regressions were then performed to compare respective frequencies and changes in peak powers of the two signals. Fast Fourier analysis of RR and [Formula: see text]E signals showed that RR was oscillating at the same frequency than periodic breathing, i.e., ~ 0.09Hz (11s). During exercise, in these various conditions, the difference between minimum and maximum HRV peak power was positively correlated to the same change in ventilation peak power (P < 0.05). Low-frequency (LF) peak power was correlated to tidal volume (P < 0.01) and breathing frequency (P < 0.001). This study suggests that low-frequency ventilatory oscillations in hypoxia are a major contributor to the LF band power of heart rate variability. CLINICAL TRIAL REG. NO.: NCT02201875.