Changes In High Frequency Power Research Articles

The Indices of Instantaneous Pulse Rate Variability Are Indicators for Daily Life Quality Assessment in Patients with COPD.

Chronic obstructive pulmonary disease (COPD) is a progressive respiratory illness. Questionnaires such as modified Medical Research Council (mMRC) dyspnea scale and COPD assessment test (CAT) are useful for COPD condition and life quality assessment. These questionnaires reflect how respiratory disorder affects daily life. Breathing and autonomic nervous system (ANS) usually regulate each other. Few studies discussed the ANS activity and daily life quality in patients with COPD. Therefore, this study aimed to find the relationship between daily life quality assessed by mMRC or CAT and ANS assessed by a novel method, instantaneous pulse rate variability (iPRV), a method indicating not only the ANS activity but also the peripheral response. The result showed that the change in mMRC and the change in low frequency power to high frequency power ratio, which usually represents the sympathetic activity in conventional heart rate variability analysis, had significant correlation (r = 0.63; p < 0.05). The change in CAT and the change in high frequency power (regulated by vagal nervous and respiratory system) or very high frequency power (new frequency band can be indicated in iPRV spectrum) had significant negative correlation (r = −0.64 and −0.55, respectively; p < 0.05 for both). This study showed the change in iPRV indices when the condition of COPD was improvement or exacerbation. This study presents a possible way to show how cardiovascular activity affects daily life quality in patients with COPD. Increase in LF or decrease in HF and VHF would cause poorer quality of daily life in patients with COPD. The result can also be a reference for patients with COPD to choose the breathing type to adjust rehabilitation and therapy program for ANS regulation to indicate or improve their daily life quality.

Effects of Lower Limb Vibrations in the Supine Position on Autonomic Activity in Healthy Adults

Background: Short duration massage of the lower limbs reduces fatigue sensation in working adults. However, the effects of lower limb vibrations on autonomic activity, which potentially could improve sleep onset, have not been fully investigated. This study aimed to examine the effects of lower limb vibrations on heart rate variability (HRV) as a marker of autonomic activity. Methods: The study involved two aspects. In the first experiment, the optimal frequency of vibration was determined in five healthy adults (one male and four females; mean age, 20.4 ± 0.5 years). The second experiment involved assessing the effects of vibration at the optimal frequency on nine healthy adults (four males and five females; mean age, 26.3 ± 16.8 years). Electrocardiograms (recorded with bipolar lead CM5) were obtained in the supine position, and HRV was used as an index for autonomic activity. The power spectra at 0.04-0.15 Hz (low frequency (LF) power) and 0.15-0.40 Hz (high frequency (HF) power) were quantified, and HF power and LF/HF ratio were calculated. In the first experiment, vibrations at four different frequencies (i.e., 25, 30, 35, and 40 Hz) were randomly applied for 10 minutes. In the second experiment, HF power and LF/HF ratio were measured at a vibration frequency of 35 Hz for 10 minutes and for 10 minutes of interruption. As a control, HF power and LF/HF ratio were recorded for 20 minutes without vibration. Findings: The percent change in HF power tended to be higher at a vibration frequency of 35 Hz compared to vibrations at frequencies of 25, 30, and 40 Hz. Vibrations at this frequency significantly increased HF power and reduced the LF/HF ratio compared to when vibrations were not applied. Conclusion: Our findings suggest that the lower limbs vibration in the supine position at the frequency of 35 Hz may increase parasympathetic activity and presumably promote the rapid onset of sleep.

The effect of fluid overload by saline infusion on heart rate variability in men during sleep.

Fluid shift from the legs and into the neck during sleep has been shown to increase tissue pressure around the upper airway and increase sleep apnea severity. Recently, acute fluid overload via saline infusion during sleep was shown to increase sleep apnea severity in an older men (≥ 40 years of age) but not the younger men (<;40 years of age). The purpose of this study was to estimate the changes in the autonomic nervous system response to saline infusion in the younger and older men using well studied time- and frequency domain heart rate variability metrics (HRV). Eighteen healthy men (10 in the younger group and 8 in the older group) slept for up to 3 hours during the day while ≈ 2L of saline was intravenously injected during sleep. An electrocardiogram was collected continuously during the sleep period. Two five minute segments of stage 1 or 2 sleep were selected for analysis of HRV: one before saline infusion and one after completion of saline infusion. Time- and frequency domain metrics of HRV were used to characterize autonomic nervous system response. Results generally showed increased HRV as measured by time-domain statistical measures in the younger men after saline infusion. In the frequency domain, the change in high frequency power from pre- to post-saline infusion was significantly greater in the younger compared to the older men. In addition, there was a borderline significant trend showing an increase in HF power from pre- to post-saline infusion in the younger, but not the older men. These results suggest that only in the younger men and not the older men, parasympathetic nervous activity increased in response to acute fluid overload. This might be one of the mechanisms that increased the severity of OSA in older and not the younger men.

Ontogeny and control of the heart rate power spectrum in the last third of gestation in fetal sheep

Power spectral analysis of fetal heart rate variability has been proposed to provide a non-invasive estimate of autonomic balance. However, there are few systematic data before birth. We therefore examined developmental changes in the frequency power spectrum at very low (0-0.04 Hz), low (0.04-0.15 Hz) and high frequencies (0.15-0.4 Hz), as well as the ratio of low- to high-frequency power (LF/HF), in chronically catheterized, healthy fetal sheep at 0.6 (n = 8), 0.7 (n = 7) and 0.8 gestational age (ga; n = 11). In a second study, 0.8 ga fetuses received either atropine (4.8 mg bolus, then 4.8 mg h(-1) for 30 min, n = 6) or 6-hydroxydopamine (20 mg ml(-1) at 2.5 ml h(-1) for 3 h; n = 9). Data were analysed by sleep state, defined by low-voltage-high-frequency (LV) or high-voltage-low-frequency (HV) EEG. Total spectral power increased with gestational age (P < 0.05), while LF/HF decreased from 0.6 to 0.7 ga. At 0.8 ga, heart rate and LF/HF were significantly higher during HV than LV sleep (P < 0.05). Consistent with this, although total spectral power was not significantly greater during HV sleep, there was a significant interaction between sleep state and frequency band (P = 0.02). Both atropine (P = 0.05) and 6-hydroxydopamine (P < 0.05) were associated with an overall reduction in spectral power but no significant effect on the LF/HF ratio. This study does not support substantial, consistent differences between the frequencies of sympathetic and parasympathetic activity in late-gestation fetal sheep.

S17-2. High-frequency electroencephalographic activity in childhood epilepsy

High-frequency (HF) activity in electroencephalogram (EEG) is closely related to both epileptogenicity/ictogenicity and physiological cognitive function. HF activity beyond the beta band includes the gamma, ripple, and fast ripple bands. We have investigated HF activity in children with epileptic encephalopathy. In the pathophysiology of epileptic encephalopathy, cognitive impairment is suggested to be linked to scalp epileptic gamma rhythms that may represent the slower part of cortical HF oscillations in West syndrome. In epilepsy with continuous spike-waves during slow wave sleep (CSWS), the disturbance of higher brain functions may be related to spike-associated scalp ripple oscillations. HF oscillations have also been detected from the ictal cortical EEG of a rat model of channelopathy with SCN1A mutation. The technique to explore HF activity, however, is demanding and requires further development. A statistical comparison of HF activity through a time–frequency analysis between epileptic discharges and the background allows an objective identification of changes in HF power. Although the obtained statistical spectrum is noisy in the uncontrolled form, it can be rendered noiseless and easy to interpret with a control technique that employs the false discovery rate (FDR).

Effects of Acupuncture on Heart Rate Variability in Beagles; Preliminary Results

Evidence-based animal experimental research concerning the effects of acupuncture on autonomic function was performed by two research teams from China and Austria. This study describes measurements in beagles. Heart rate variability (HRV) recordings were performed under stable conditions in Beijing, China, and the data analysis and interpretation were completed in Graz, Austria. The electrocardiograms were recorded during bilateral body acupuncture (PC6, Neiguan). Power of the low frequency (LF), high frequency (HF), and the ratio (LF/HF) changed significantly during acupuncture stimulation in beagles after injection of atropine and β-blocker. However, there was no significant change in HF power after needling the Neiguan acupoint when a cervical vagotomy has been performed. Our findings show that acupuncture can mediate the HRV even after pharmaceutical blocking of autonomic function. Acupuncture effects on HRV should rely not only on autonomic nervous system but on complete central nervous system.

Behavioural modification of the cholinergic anti‐inflammatory response to C‐reactive protein in patients with hypertension

A central hypothesis of the cholinergic anti-inflammatory reflex model is that innate immune activity is inhibited by the efferent vagus. We evaluated whether changes in markers of tonic or reflex vagal heart rate modulation following behavioural intervention were associated inversely with changes in high-sensitivity C-reactive protein (hsCRP) or interleukin-6 (IL-6). Subjects diagnosed with hypertension (n = 45, age 35-64 years, 53% women) were randomized to an 8-week protocol of behavioural neurocardiac training (with heart rate variability biofeedback) or autogenic relaxation. Assessments before and after intervention included pro-inflammatory factors (hsCRP, IL-6), markers of vagal heart rate modulation [RR high-frequency (HF) power within 0.15-0.40 Hz, baroreflex sensitivity and RR interval], conventional measures of lipoprotein cholesterol and 24-h ambulatory systolic and diastolic blood pressure. Changes in hsCRP and IL-6 were not associated with changes in lipoprotein cholesterol or blood pressure. After adjusting for anti-inflammatory drugs and confounding factors, changes in hsCRP related inversely to changes in HF power (β = -0.25±0.1, P = 0.02), baroreflex sensitivity (β = -0.33±0.7, P = 0.04) and RR interval (β = -0.001 ± 0.0004, P = 0.02). Statistically significant relationships were not observed for IL-6. Changes in hsCRP were consistent with the inhibitory effect of increased vagal efferent activity on pro-inflammatory factors predicted by the cholinergic anti-inflammatory reflex model. Clinical trials for patients with cardiovascular dysfunction are warranted to assess whether behavioural interventions can contribute independently to the chronic regulation of inflammatory activity and to improved clinical outcomes.

The fMRI BOLD signal tracks electrophysiological spectral perturbations, not event-related potentials

Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are primary tools of the psychological neurosciences. It is therefore important to understand the relationship between hemodynamic and electrophysiological responses. An early study by Huettel and colleagues found that the coupling of fMRI blood-oxygen-level-dependent signal (BOLD) and subdurally-recorded signal-averaged event-related potentials (ERPs) was not consistent across brain regions. Instead, a growing body of evidence now indicates that hemodynamic changes measured by fMRI reflect non-phase-locked changes in high frequency power rather than the phase-locked ERP. Here, we revisit the data from Huettel and colleagues and measure event-related spectral perturbations (ERSPs) to examine the time course of frequency changes. We found that, unlike the ERP, γ-ERSP power was consistently coupled with the hemodynamic response across three visual cortical regions. Stimulus duration modulated the BOLD signal and the γ-ERSP in the peri-calcarine and fusiform cortices, whereas there was no such modulation of either physiological signal in the lateral temporal-occipital cortex. This finding reconciles the original report with the more recent literature and demonstrates that the ERP and ERSP reflect dissociable aspects of neural activity.

The role of inhibitory heterotrimeric G proteins in the control of in vivo heart rate dynamics

Multiple isoforms of inhibitory Galpha-subunits (Galphai1,2,3, as well as Galphao) are present within the heart, and their role in modulating pacemaker function remains unresolved. Do inhibitory Galpha-subunits selectively modulate parasympathetic heart rate responses? Published findings using a variety of experimental approaches have implicated roles for Galphai2, Galphai3, and Galphao in parasympathetic signal transduction. We have compared in vivo different groups of mice with global genetic deletion of Gialpha1/Galphai3, Galphai2, and Galphao against littermate controls using implanted ECG telemetry. Significant resting tachycardia was observed in Galphai2(-/-) and Galphao(-/-) mice compared with control and Galphai1(-/-)/Galphai3(-/-) mice (P < 0.05). Loss of diurnal heart rate variation was seen exclusively in Galphao(-/-) mice. Using heart rate variability (HRV) analysis, compared with littermate controls (4.02 ms2 +/- 1.17; n = 6, Galphai2(-/-)) mice have a selective attenuation of high-frequency (HF) power (0.73 ms2 +/- 0.31; n = 5, P < 0.05). Galphai1(-/-)/Galphai3(-/-) and Galphao(-/-) cohorts have nonsignificant changes in HF power. Galphao(-/-) mice have a different basal HRV signature. The observed HRV phenotype in Galphai2(-/-) mice was qualitatively similar to atropine (1 mg/kg)-treated controls [and mice treated with the GIRK channel blocker tertiapinQ (0.05 mg/kg)]. Maximal cardioinhibitory response to the M(2)-receptor agonist carbachol (0.5 mg/kg) compared with basal heart rate was attenuated in Galphai2(-/-) mice (0.08 +/- 0.04; n = 6) compared to control (0.27 +/- 0.04; n = 7 P < 0.05). Our data suggest a selective defect of parasympathetic heart rate modulation in mice with Galphai2 deletion. Mice with Galphao deletion also have a defect in short-term heart rate dynamics, but this is qualitatively different to the effects of atropine, tertiapinQ, and Galphai2 deletion. In contrast, Galphai1 and Galphai3 do not appear to be essential for parasympathetic responses in vivo.

Effects of increased physical activity and mild calorie restriction on heart rate variability in obese women.

The effects of exercise and mild calorie restriction on heart rate variability (HRV) were investigated in 12 mildly obese, normotensive Japanese women aged 45.8+/-4.2 (SEM) years with a body mass index (BMI) of 27.3+/-0.4 kg/m2. The subjects participated in a 3-month program aimed at increasing physical activity and modifying eating behavior (intervention group). The control group consisted of 12 women (age 50.1+/-4.8 years, BMI 27.2+/-0.6 kg/m2) who did not attend the program. The frequency domain of HRV was calculated from 5-min Holter recordings while the subjects rested in a supine position. After 3 months, BMI decreased to 25.0+/-0.5 kg/m2 (p<0.001 vs baseline) in the intervention group, which was accompanied by decreases in body fat mass, waist circumference, serum total cholesterol and triglycerides, and improvement in insulin sensitivity. The mean and SD of the RR intervals, total power, and low and high frequency power of HRV significantly increased after the intervention, whereas no significant changes were seen for the controls. The changes in these HRV variables (calculated by subtracting the baseline values from the follow-up values) negatively correlated with the change in waist circumference, with the Pearson correlation coefficients being between -0.50 and -0.62 (p<0.05). A negative correlation was also seen between the changes in high frequency power and insulin resistance estimated by homeostasis model assessment (r=-0.49, p<0.05). The combination of exercise and mild calorie restriction led to changes in HRV indicative of an improvement in parasympathetic modulation.