Coordination of the EEG and the heart rate of preterm neonates during quiet sleep

Aim of this study was to confirm that EEG bursts are associated with heart rate (HR) accelerations, and to investigate the synchronicity between quadratic phase couplings (QPC) courses of the EEG and HR before and during burst activity during quiet sleep in preterm newborns. The time-courses of QPC between frequency components of the EEG ([0.25–1.0 Hz] ↔ [4.0–6.0 Hz]) as well as between the Mayer–Traube–Hering (MTH) wave and the frequency component of the HR associated to the respiratory sinus arrhythmia (RSA) ([0.02–0.15 Hz] ↔ [0.4–1.5 Hz]) were investigated in five preterm neonates. During quiet sleep, the EEG alternates between burst and interburst activity. The burst onsets were used to trigger an averaging procedure for the EEG, HR, and QPC courses. It can be demonstrated that the envelopes of the EEG rise after the burst onset accompanied by an acceleration of HR before or at the burst maximum. The QPC courses show that the HR's QPC increases before or at the burst onset whereas the increase of the EEG's QPC is delayed. The synchronous changes of EEG and HR as well as of the corresponding QPC courses indicate a coupling between cortical, thalamocortical and neurovegetative brain structures. Such a coupling might be mediated by the MTH waves in the blood pressure.     

Effect of low-dose endurance training on heart rate variability at rest and during an incremental maximal exercise test

We evaluated the effects of low-dose endurance training on autonomic HR control. We assessed the heart rate variability (HRV) of 11 untrained male subjects (36.8 +/- 7.2 years) at rest and during an incremental maximal aerobic exercise test prior to a 7-week preparatory period and prior to and following a 14-week endurance training period, including a low to high intensity exercise session twice a week. Total (0.04-1.2 Hz), low (0.04-0.15 Hz) and high (0.15-1.2 Hz) frequency power of HRV were computed by short-time Fourier transform. The preparatory period induced no change in aerobic power or HRV. The endurance training period increased peak aerobic power by 12% (P < 0.001), decreased the HR (P < 0.01) and increased all HRV indices (P < 0.05-0.01) at absolute submaximal exercise intensities, but not at rest. In conclusion, low-dose endurance training enhanced vagal control during exercise, but did not alter resting vagal HR control.     

Heart rate variability and endogenous sex hormones during the menstrual cycle in young women

To our knowledge, the relationship between all four endogenous female sex hormones and resting cardiac autonomic function has not been studied. The aim of the current study was to examine the association between the normal endogenous levels of oestrogen (17beta-oestradiol), progesterone, luteinising hormone and follicle-stimulating hormone and heart rate variability (HRV) during the menstrual cycle in young eumenorrheic women. Ten healthy, young, female subjects volunteered for this study. HRV and endogenous hormone levels were recorded at three phases of the menstrual cycle: menses (day 3.8 +/- 0.5), ovulation (day 15.8 +/- 0.7) and luteal (day 22.1 +/- 0.4) to ensure HRV recordings at times of low (menses) and high (ovulation and luteal) hormonal influence. Heart rate recordings were obtained from supine resting subjects and analysed on a Holter analysis system. Total power (TP, 0-1.0 Hz), low frequency (LF, 0.041-0.15 Hz), high frequency (HF, 0.15-0.80 Hz) and LF/HF components of HRV were examined. Despite a significantly greater HR at ovulation and normal cyclic variations in all endogenous sex hormone levels, no measure of HRV was significantly different between menstrual cycle phases. Significant correlations between oestrogen levels and absolute measures of HRV at ovulation were identified. The results of the current study demonstrated that the normal cyclic variations in endogenous sex hormone levels during the menstrual cycle were not significantly associated with changes in cardiac autonomic control as measured by HRV. Significant correlation between peak oestrogen levels and HRV measures at ovulation provided further support for the reported cardioprotective effects of oestrogen in healthy females.     

The influence of exercise intensity on the power spectrum of heart rate variability

Summary The power spectral analysis of R-R interval variability (RRV) has been estimated by means of an autoregressive method in seven sedentary males at rest, during steady-state cycle exercise at 21 percent maximal oxygen uptake. (% V _{O 2max}), SEM 2%, 49% V_{O 2max}, SEM 2% and 70% V_{O 2max}, SEM 2% and during recovery. The RRV, i.e. the absolute power of the spectrum, decreased 10, 100 and 500 times in the three exercise intensities, returning to resting value during recovery. In the RRV power spectrum three components have been identified: (1) high frequency peak (HF), central frequency about 0.24 Hz at rest and recovery, and 0.28 Hz, SEM 0.02, 0.37 Hz, SEM 0.03 and 0.48 Hz, SEM 0.06 during the three exercise intensities, respectively; (2) low frequency peak (LF), central frequency about 0.1 Hz independent of the metabolic state; (3) very low frequency component (VLF), <0.05 Hz, no peak observed. The HF peak power, as a percentage of the total power (HF%), averaged 16%, SEM 5% at rest and did not change during exercise, whereas during recovery it decreased to 5%–10%. The LF% and VLF% were about 50% and 35% at rest and during low exercise intensity, respectively. At higher intensities, LF% decreased to 16% and VLF% increased to 70%. During recovery a return to resting values occurred. The HF component may reflect the increased respiratory rate and the LF peak changes the resetting of the baroreceptor reflex with exercise. The hypothesis is made that VLF fluctuations in heart rate might be partially mediated by the sympathetic system.     

女大学生月经周期应激敏感性的生理心理评估

目的:评估女大学生在月经周期不同阶段应激敏感性的变化。方法:在经前、经后和排卵期对29名月经周期规律的女大学生进行静息、心算任务的心理生理测试。结果:心率变化最显著,排卵期的心率显著大于经前和经后;在排卵期和经后心算心率显著大于静息心率,而在经前两者之间无显著差异;在心率变异性上,仅发现低频成分在静息状态显著大于心算状态;皮肤电反应在心算状态显著大于静息状态。结论:女大学生在经前应激敏感性最高。     

Changes in Mood and Autonomic Functioning During the Menstrual Cycle

The autonomic nervous system activity and mood ratings of 12 women were studied 6 days a week for a complete menstrual cycle. The daily procedure consisted of a resting period, a series of 5 mild tones, time estimation (TE), and reaction time (RT) trials, and a final resting period. Significant increase in heart rate (HR), respiration rate, and body temperature, and a significant decrease in resting skin conductance (SC) were found during the luteal phase. During the ovulatory phase there were significant increases in autonomic responsivity, as shown by greater amplitude of SC response in the TE and RT situations as well as in faster SC drop-rate and greater HR variability. All of these autonomic variability measures coincided with a significant peak in feelings of elation and vigor. Significant age effects were that older women had higher basal body temperatures, less marked HR variability, and tended to have lower levels of SC, particularly in the luteal phase of the cycle. The results are discussed in terms of the psychophysiological effects of estrogen and progesterone.     

Vagally mediated heart rate variability and heart rate entropy as predictors of treatment outcome in flight phobia

In the present study a computer-assisted exposure-based treatment was applied to 54 flight phobics and the predictive role of vagally mediated heart rate (HR) variability (high frequency, 0.15-0.4 Hz band power) and heart rate entropy (HR time series sample entropy) on treatment outcome was investigated. Both physiological measures were taken under controlled breathing at 0.2 Hz and during exposure to a fearful sequence of audiovisual stimuli. Hierarchical regression analyses were conducted to assess the predictive power of these variables in these conditions on treatment self-report measures at the end of treatment and at 6 months follow-up, as well as on the behavioral treatment outcome (i.e. flying at the end of treatment). Regression models predicting significant amounts of outcome variance could be built only when HR entropy was added to the HR variability measure in a second step of the regression analyses. HR variability alone was not found to be a good predictor of neither self-reported nor behavioral treatment outcomes.     

Tobacco withdrawal in women and menstrual cycle phase

Because negative mood is a characteristic of both tobacco withdrawal and menstrual discomfort, withdrawal may vary by menstrual cycle phase. Tobacco withdrawal, mood, and menstrual discomfort were assessed in premenopausal women who quit smoking during either the follicular (Days 1-14 postmenstrual onset; n = 41) or luteal (Day 15 or longer postmenstrual onset; n = 37) phase of the menstrual cycle and maintained biochemically verified smoking abstinence during the postquit week. Women quitting during the luteal phase reported significantly greater increases in tobacco withdrawal and self-reported depressive symptoms than women quitting during the follicular phase. These results indicate that selecting a quit-smoking day early in the follicular phase may attenuate withdrawal and negative affect in premenopausal female smokers.     

Auditory brainstem response in premenopausal women taking oral contraceptives

BACKGROUND: The aim of this prospective study was to evaluate the effects of the new monophasic oral contraceptives on the audiological system in premenopausal women. METHODS: The auditory brainstem response (ABR) was measured in 94 women during the follicular, periovular and luteal phases of one menstrual cycle in which ovulation was confirmed using sonography and serum progesterone concentration. The latencies for waves I, III and V were determined, and the inter-peak intervals were calculated for waves I-III, I-V and III-V. All 94 women began taking oral contraceptives: 23 women used 20 microg ethinyl estradiol (EE) plus 150 microg desogestrel, 24 women used 30 microg EE plus 75 microg gestodene, and 47 women used 15 microg EE plus 60 microg gestodene. During the third month of contraceptive intake, each subject was again tested for ABR, as above. RESULTS: The wave latencies and inter-peak intervals showed shorter values during the periovular phase with respect to the luteal phase (P < 0.05), the follicular phase for wave I and for inter-peak interval I-V (P < 0.05) of the menstrual cycle. All of the ABR results in pill users were statistically different from those of the periovular phase (P < 0.05), though similar to those of both the luteal and follicular phases (P = NS). CONCLUSIONS: ABR seems to depend on the variations of ovarian steroids during the menstrual cycle and during oral contraceptive intake.     

驾驶精神疲劳的心率变异性和血压变异性综合效应分析

驾驶精神疲劳是威胁人们健康与生命安全的严重问题.本研究的目的是基于心率变异性与血压变异性功率谱分析综合评估驾驶员精神疲劳.20个健康男性样本(28.8±4.3)岁参加90 min的模拟驾驶操作实验,实验后计算分析实验样本心率变异性和血压变异性的频域指标,如:低频成分(0.04～0.15 Hz,LF),高频成分(0.15～0.4Hz,HF),代频与高频比值(LF/HF);同时分析反映血流动力学指标的血压和心率.研究表明,样本在实验结束后交感神经兴奋性增强,迷走神经兴奋性减弱,交感迷走平衡性升高;同时,心率变异性与血压变异性的对应指标在实验过程中具有良好的相关性(P＜0.05).研究认为采用多变量综合效应分析方式评价自主神经系统功能是科学和客观的.     

Effects of mental and physical demands on heart rate variability during computer work

The aim of the study was to evaluate the effect of physical and mental demands on heart rate variability- (HRV-) derived indices of autonomic activity. Ten healthy, female subjects performed two computer tasks: one with combined mental and physical demands and a reference task primarily consisting of physical demands. The combined task, which was performed once with a keyboard and once with a computer mouse, was a computerized version of the colour word conflict task (CWT). The CWT is highly mentally demanding due to the inherent perceptual conflict between a word stimulus and a colour stimulus. In the reference task (REF) the physical demands were comparable to CWT, while the mental demands were low. Finally, the subjects rested at the workplace (REST). Data on performance, heart rate (HR), mean arterial blood pressure (MAP), HRV, and urinary concentrations of catecholamines were obtained. The following frequency bands were applied for HRV: very low frequency (VLF, 0.00–0.04 Hz), low frequency (LF, 0.05–0.15 Hz), high frequency (HF, 0.16–0.40 Hz) and total power (TP, 0.00–0.40 Hz). Indices of sympathetic nervous activity (I_SNS) and parasympathetic nervous activity (I_PNS) were estimated as normalized powers in LF and HF bands: I_SNS=LF/(TP–VLF) and I_PNS=HF/(TP–VLF). Values are expressed as normalised units (nu). There was an increase in I_SNS during CWT [mouse: 0.490 (0.052) nu [ave (SEM)] and keyboard: 0.476 (0.039) nu] and REF [mouse: 0.453 (0.059) nu and keyboard: 0.489 (0.047) nu] compared to REST [0.397 (0.047) nu], but no difference between CWT and REF. Corresponding decreases were observed for I_PNS. HR and MAP were higher during CWT compared to REST. No effects were observed for excreted amounts of catecholamines. There were no differences between the computer mouse and the keyboard condition for I_SNS and I_PNS. In conclusion, an increase in I_SNS and a decrease in I_PNS were found in response to a physically demanding reference computer task. Addition of mental demands did not elicit any further effect on I_SNS and I_PNS, suggesting a significant influence of the physical rather than the mental demands during computer work. Electronic Publication     

Consistency of heart rate and sympathovagal reactivity across different autonomic contexts

Theories that psychophysiological reactivity constitutes a risk factor for coronary artery disease assume that reactivity is a consistent individual characteristic. We tested this assumption by measuring reactivity to three psychologically challenging tasks performed by 22 healthy subjects across different autonomic contexts produced by positional change. Dependent variables included heart rate (HR), low-frequency (LF; 0.04–0.15 Hz) and high-frequency (HF; 0.15–0.50Hz) heart period variability, and the LF/HF ratio. HR (r= .44, p < .05) and LF/HF ratio (r= .48, p= .03) reactivity were modestly correlated across the different autonomic contexts, but HF and LF power reactivity were not. These findings suggest that HR reactivity to psychological challenge is a modestly consistent characteristic of individuals, despite differences in autonomic context. Although the same is true of cardiac sympathovagal balance, reactivity of HF and LF power were less consistent.     

Body position affects the power spectrum of heart rate variability during dynamic exercise

Summary The power spectrum analysis of R-R interval variability (RRV) has been estimated by means of an autoregressive method in six men in supine (S) and sitting (C) postures at rest and during steady-state cycle exercise at about 14010, 28%, 45%, 67% of the maximal oxygen consumption (% VO_2max). The total power of RRV decreased exponentially as a function of exercise intensity in a similar way in both postures. Three components were recognized in the power spectra: firstly, a high frequency peak (HF), an expression of respiratory arrhythmia, the central frequency (f _central) of which increased in both S and C from a resting value of about 0.26 Hz to 0.42 Hz at 67% VO_2max; secondly, a low frequency peak (LF) related to arterial pressure control, the f _central of which remained constant at 0.1 Hz in C, whereas in S above 28% VO_2max decreased to 0.07 Hz; and thirdly, a very low frequency component (VLF; less than 0.05 Hz, no f _central). The power of the three components (as a percentage of the total power) depended on the body posture and the metabolic demand. HF% at rest was 30.3 (SEM 6.6) % in S and 5.0 (SEM 0.8) % in C. During exercise HF% decreased by about 30% in S and increased to 19.7 (SEM 5.5) % at 28% VO_2max in C. LF% was lower in S than in C at rest [31.6 (SEM 5.7) % vs 44.9 (SEM 6.4) %; P<0.05], remaining constant up to 28% VO_2max. At the highest intenstities it increased to 54.0 (SEM 15.6) % in S whereas in C it decreased to 8.5 (SEM 1.6) %. VLF represented the remaining power and the change was in the opposite direction to LF. The changes in power spectrum distribution of RRV during exercise depended on the intensity and the body posture. In particular, the LF peak showed opposite trends in S and C tasks, thus suggesting a different readjustment of arterial pressure control mechanisms in relation to the blood distribution and peripheral resistances.     

AKAP10 (I646V) functional polymorphism predicts heart rate and heart rate variability in apparently healthy, middle-aged European-Americans

Previous evidence suggests that the dual-specific A kinase-anchoring protein 2 functional polymorphism (AKAP10 (A/G) I646V) influences heart rate (HR) and heart rate variability (HRV) in mice and humans ( N =122) with cardiovascular disease. Here, we asked whether this AKAP10 variant predicts HR and HRV in a large sample of healthy humans. Resting HR and short-term time and frequency domain measures of HRV (5 min during paced and unpaced respiration conditions) were assessed in a U.S. community sample ( N =1,033) of generally healthy men and women (age 30–54) of European ancestry. Each person was genotyped for the AKAP10 variant. As with previous work, the AKAP10 Val allele predicted greater resting HR (Paced p <.01; Unpaced p <.03) and diminished HRV (Paced p s <.05) suggesting that this variant may modulate the sensitivity of cardiac pacemaker cells to autonomic inputs, possibly conferring risk for arrhythmias and sudden cardiac death.     

Mechanisms underlying hemodynamic and neuroendocrine stress reactivity at different phases of the menstrual cycle

This study examined the association of menstrual cycle phase with stress reactivity as well as the hormonal and neuroendocrine mechanisms contributing to cycle effects. Fifty‐seven women underwent a modified Trier Social Stress Test during the early follicular, late follicular, and luteal phases of the menstrual cycle. Greater increases in cardiac index (CI) and greater decreases in vascular resistance index (VRI) during speech were observed in the luteal phase relative to other phases, while greater increases in epinephrine (EPI) was observed during the late follicular and luteal phases compared to the early follicular phase. Luteal phase estradiol predicted luteal EPI reactivity but not CI or VRI reactivity, while luteal phase EPI reactivity predicted luteal phase CI and VRI reactivity. Thus, cycle‐related changes in EPI reactivity may be a stronger determinant of cycle effects on hemodynamic reactivity than sex hormones per se.     

The heart rate increase at the onset of high-work intensity exercise is accelerated by central blood volume loading

Using a water immersion (WI) method, the combined effect of central blood volume (CBV) loading and work intensity on the time course of heart rate (HR) at the onset of upright dynamic exercise was investigated. Seven males cranked a cycle ergometer for 12 min using their un-immersed arms at low-, moderate- and high-work intensities, followed by a 12-min rest. For WI, the pre-exercise resting cardiac output increased by 36%, while HR decreased by 22% [from 76.8 (10.4) to 59.6 (9.8) beats/min]. WI also increased the high-frequency (HF, 0.15–0.40 Hz) component of the HR variability, suggesting an increased vagal activity. During the initial 2 min of the exercise period at low-work intensity, HR increased by 34.9 and 25.8% in the WI and control conditions, respectively. These were 117 and 73% at high-work intensity, indicating more accelerated HR with WI than the control. The plasma norepinephrine concentration increased less during high-work intensity exercise during WI, as compared to exercise during control conditions. In conclusion, the HR increase at the onset of high-work intensity exercise is accelerated by CBV loading but not at low intensity, possibly reflecting vago-sympathetic interaction and reduced baroreflex sensitivity.     

Somatomotor related hippocampal rhythmic slow activity in the monkey (Macaca mulatta)

Hippocampal rhythmic slow activity (RSA) and its relation to somatomotor activity and heart rate (HR) were assessed in 128 sec observation periods in 2 monkeys under three behavioral conditions, i.e., look (at experimenter); reach (for food); struggle (against restraint); and one control condition (no monkey-experimenter interaction) which was interspersed between each behavioral condition. Two measures of hippocampal activity (in addition to HR) were taken: (1) percent RSA/128 sec (from filtered, 4–8 Hz, integrated signal); (2) Spectral analysis of unfiltered activity from first 10 sec of each observation period. Spectral analyses were done over 1–3, 4–8, 9–12, 13–20 Hz bands. Results showed that the greatest increases in RSA and HR were present during intense somatomotor activity (struggle condition) for both animals. RSA was variable during the reach and look conditions. RSA and HR were highly correlated under all conditions. Spectral analyses showed that reliable changes in energy were limited to the 4–8 Hz band. Results are discussed in terms of RSA-HR-somatomotor relationships in primates and infraprimates.     

Temporal stability of heart period variability during a resting baseline and in response to psychological challenge

Central to the psychophysiologic reactivity hypothesis of the etiology of coronary artery disease is the assumption that reactivity is an individual characteristic that is stable over time. Although heart rate (HR) and blood pressure reactivity appear to meet this criterion, temporal stability of cardiac autonomic control as measured by analysis of heart period variability (HPV) has not been assessed. In this study, we tested the stability of HPV, measured in both the time and frequency domain, during a quiet, resting baseline and in response to 5-min mental arithmetic and reaction time tasks, in 20 normal subjects measured in three testing sessions during a 9-month period. Stability, assessed by the intraclass correlation coefficient (ICC), was excellent for resting baseline measures of HR and HPV, with ICCs of 0.68–0.86. However, HR and HPV reactivity to either arithmetic or reaction time tasks generally was less stable, with ICCs of 0.17–0.73, in contrast to results of previous studies demonstrating long-term Stability of HR responses to psychological challenge. Stability of aggregated reactivity scores was only slightly improved. Whether for individual tasks or aggregated measures, reactivity of total and low-frequency measures of HPV was moderately stable but stability of high-frequency HPV reactivity was poor.     

The effects of 1-month administration of asoprisnil (J867), a selective progesterone receptor modulator, in healthy premenopausal women

BACKGROUND: Asoprisnil (J867) is a novel selective progesterone receptor modulator (SPRM) that exhibits partial agonist and antagonist activities and tissue selective effects. This double-blind, dose-escalation study was conducted to evaluate the effects of asoprisnil in 60 regularly cycling premenopausal women. METHODS: Asoprisnil or placebo was administered orally for 28 days starting at the beginning of the menstrual cycle in doses of 5 mg once daily (QD), 5 mg twice daily (BID), 10 mg QD, 25 mg QD, 25 mg BID and 50 mg BID. Within each dose group, two women were randomized to placebo and eight to asoprisnil. Progesterone concentrations indicative of luteinization were defined as at least one progesterone measurement during the luteal phase exceeding 3.5 ng/ml. RESULTS: Asoprisnil consistently prolonged the menstrual cycle at doses > or = 10 mg QD. However, the effects on luteal phase progesterone indicative of luteinization were inconsistent and lacked dose dependency. Asoprisnil suppressed periovulatory estradiol but not below follicular phase levels. No significant changes were observed in cortisol and prolactin. Asoprisnil was well tolerated. CONCLUSIONS: Asoprisnil reversibly suppressed menstruation at doses > or = 10 mg QD irrespective of the effect on luteal phase progesterone concentrations indicative of luteinization. It induces amenorrhea primarily by targeting the endometrium in the absence of estrogen deprivation.     

Daily self-sampling for high-risk human papillomavirus (HR-HPV) testing

BackgroundSelf-sampling for HPV as part of primary screening is a well-tolerated method for women not attending organized Pap smear screening and could increase coverage of cervical cancer screening.ObjectiveTo investigate if the prevalence of HR-HPV varies from day to day in infected women and if one single sample is reliable for detecting an ongoing infection.Study designThis is a prospective cohort study on 12 premenopausal and 13 postmenopausal women performing daily self-sampling for HR-HPV testing. They were all HR-HPV-positive 1–3 months ago. Postmenopausal women were sampled for 28 days and premenopausal women sampled during bleeding-free days in one menstrual cycle. A possible difference in viral load between the estrogen-dominated proliferative phase and the progesterone-dominated secretory phase was analyzed.Results and conclusionsConsistent results throughout the sampling period were observed for 19 women, with either a daily presence of HPV (14 women) or no HPV at all during the sampling period (5 women). Of 607 samples from 25 women, 596 were consistently positive or negative for HPV during the sampling period and 11 were inconsistent (2%). There was no difference in HPV copy number between the estrogen dominated proliferative or progesterone dominated secretory menstrual cycle phases.The major finding was a high degree of consistency concerning HR-HPV positivity and negativity of HR-HPV in vaginal fluid during a sustained period of daily self-sampling. It does not appear to matter whether the sample is collected in the proliferative or secretory phase.