The association between autonomic response status and the changes in EEG activity during mental arithmetic task

Mental arithmetic (MA) tasks have been reported to induce an increase in blood pressure and heart rate by enhancing sympathetic activity. However, there are individual differences in the change of autonomic nervous activity during MA task. In the present study, we quantitatively analyzed EEG changes and autonomic nervous activity using heart rate variability (HRV) during MA task in 38 healthy young volunteers. They were classified into two groups, stress responders and non-responders, according to whether both LF/HF and blood pressure increased above the baseline or not in response to MA. Then autonomic and EEG changes were compared between the two groups. The MA task induced an increase in slow beta power in the stress responders, whereas it induced a decrease in slow beta power in the stress non responders. Further evaluation showed a significant positive correlation between the percent change from the baseline in slow alpha power and that in LF/HF. These results suggest that there are correlations between the autonomic response in an individual and EEG power changes during MA tasks.     

Changes in EEG and autonomic nervous activity during meditation and their association with personality traits.

Meditation is the attainment of a restful yet fully alert physical and mental state practiced by many as a self-regulatory approach to emotion management, but the psychophysiological properties and personality traits that characterize this meditative state have not been adequately studied. We quantitatively analyzed changes in psychophysiological parameters during Zen meditation in 20 normal adults, and evaluated the results in association with personality traits assessed by Cloninger's Temperament and Character Inventory (TCI). During meditation, increases were observed in fast theta power and slow alpha power on EEG predominantly in the frontal area, whereas an increase in the normalized unit of high-frequency (nuHF) power (as a parasympathetic index) and decreases in the normalized unit of low-frequency (nuLF) power and LF/HF (as sympathetic indices) were observed through analyses of heart rate variability. We analyzed the possible correlations among these changes in terms of the percent change during meditation using the control condition as the baseline. The percent change in slow alpha EEG power in the frontal area, reflecting enhanced internalized attention, was negatively correlated with that in nuLF as well as in LF/HF and was positively correlated with the novelty seeking score (which has been suggested to be associated with dopaminergic activity). The percent change in fast theta power in the frontal area, reflecting enhanced mindfulness, was positively correlated with that in nuHF and also with the harm avoidance score (which has been suggested to be associated with serotonergic activity). These results suggest that internalized attention and mindfulness as two major core factors of behaviors of mind during meditation are characterized by different combinations of psychophysiological properties and personality traits.     

Assessment of autonomic nervous system with analysis of heart rate variability in children with spastic cerebral palsy

The purpose of this study was to investigate the function of the autonomic nervous system in children with spastic cerebral palsy (CP) through an analysis of heart rate variability (HRV) occurring with orthostatic stress. Twelve children with spastic CP and twelve normal children participated in this study. The echocardiogram (ECG) signals were recorded for 3 minutes in both the supine and 70 degrees C head-up tilt positions, and then the HRV signals underwent power spectrum analysis at each position. Two components were measured; a low- frequency (LF) component (0.05 - 0.15 Hz) primarily reflecting sympathetic activity during orthostatic stress and a high-frequency (HF) component (0.15 - 0.4 Hz) reflecting parasympathetic activity. In the supine position, there was no significant difference between any of the HRV components of the two groups. In the head-up tilt position, absolute and normalized LF were significantly increased and absolute HF was significantly decreased in the normal children (p < 0.05), but not in the children with spastic CP. The results of this study suggest that cardiac autonomic functions, such as vagal withdrawal and sympathetic activation which occur during head-up tilt position, are not sufficient to overcome the orthostatic stress arising in spastic CP children.     

Relationship between electroencephalogram slow-wave magnitude and heart rate variability during sleep in humans

To explore whether depth of sleep is related to changes in autonomic control, continuous power-spectral analysis of the electroencephalogram (EEG) and heart rate variability (HRV) was performed in ten normal subjects during nocturnal sleep. Quiet sleep (QS) was associated with an increase in high-frequency power (HF) of HRV (0.15-0.4 Hz) but a decrease in low-frequency power (LF) (0.04-0.15 Hz) to HF ratio (LF/HF) compared with awakening. During QS, LF/HF was significantly and negatively correlated with delta power of EEG (0.5-4.0 Hz), whereas mean R-R interval and HF were not. We conclude that during QS, cardiac sympathetic regulation is negatively related to the depth of sleep, although vagal regulation is not. Our methodology offers a quantitative analysis to study the interaction between cerebral cortical and autonomic functions.     

Relationship between electroencephalogram slow-wave magnitude and heart rate variability during sleep in rats

To explore whether depth of sleep is related to changes in autonomic control in rats, continuous power-spectral analysis of electroencephalogram (EEG) and heart rate variability (HRV) was performed in unanesthetized rats during normal daytime sleep. Quiet sleep (QS) was associated with an increase in high-frequency power of HRV (0.6-2.4 Hz, HF) but a decrease in low-frequency power (0.06-0.6 Hz) to HF ratio (LF/HF) compared with awakening. During QS, LF/HF was significantly and negatively correlated with delta power of EEG (0.5-4.0 Hz), whereas mean R-R interval and HF were not. As in humans, cardiac sympathetic regulation in rats is negatively related to the depth of sleep during QS, although vagal regulation is not. Our methodology offers a parallel way of studying the interaction between cerebral cortical and autonomic functions in rats.     

Scatterplot analysis of EEG slow-wave magnitude and heart rate variability: an integrative exploration of cerebral cortical and autonomic functions

STUDY OBJECTIVES: To explore interactions between cerebral cortical and autonomic functions in different sleep-wake states. DESIGN: Active waking (AW), quiet sleep (QS), and paradoxical sleep (PS) of adult male Wistar-Kyoto rats (WKY) on their daytime sleep were compared. PARTICIPANTS: Ten WKY. INTERVENTIONS: All rats had electrodes implanted for polygraphic recordings. One week later, a 6-hour daytime sleep-wakefulness recording session was performed. MEASUREMENTS AND RESULTS: A scatterplot analysis of electroencephalogram (EEG) slow-wave magnitude (0.5-4 Hz) and heart rate variability (HRV) was applied in each rat. The EEG slow-wave-RR interval scatterplot from all of the recordings revealed a propeller-like pattern. If the scatterplot was divided into AW, PS, and QS according to the corresponding EEG mean power frequency and nuchal electromyogram, the EEG slow wave-RR interval relationship became nil, negative, and positive for AW, PS, and QS, respectively. A significant negative relationship was found for EEG slow-wave and high-frequency power of HRV (HF) coupling during PS and for EEG slow wave and low-frequency power of HRV to HF ratio (LF/HF) coupling during QS. The optimal time lags for the slow wave-LF/HF relationship were different between PS and QS. CONCLUSIONS: Bradycardia noted in QS and PS was related to sympathetic suppression and vagal excitation, respectively. The EEG slow wave-HRV scatterplot may provide unique insights into studies of sleep, and such a relationship may delineate the sleep-state-dependent fluctuations in autonomic nervous system activity.     

The relationships between autonomic function and heart rate in essential hypertension

The circadian variation of blood pressure (BP) may be mediated at least in part by circadian variation of autonomic nervous system activity. In the present study power spectral analysis of hourly R-R intervals for 24 hours was done to obtain the low frequency variability (LF: 0.04 to 0.15Hz) and high frequency variability(HF: 0.15 to 0.40Hz) in 93 patients with untreated essential hypertension. LF/HF ratio and HF were considered to be an index of sympathetic nervous activity and parasympathetic nervous activity, respectively. The relationship between heart rate (HR) and systolic blood pressure (SBP), diastolic blood pressure (DBP), HF, and LF/HF was examined. Both SBP and DBP were correlated positively with HR(r = 0.28, p < 0.05 and r = 0.27, p < 0.05, respectively) in the daytime. HF was correlated negatively and significantly with HR in both daytime and nighttime (r = -0.40, p < 0.05, and r = -0.38, p < 0.05 respectively). After averaging for SBP of 24 hours, HR in the patients whose SBP was 135mmHg or more was significantly higher than that in the patients whose SBP was less than 135mmHg. These results suggest that the decreased parasympathetic nervous activity seems to be responsible for the rise in BP.     

Asymmetry in sympathetic and vagal activities during sleep-wake transitions

STUDY OBJECTIVES: To explore the role of autonomic nervous system in initiation of sleep-wake transitions. DESIGN: Changes in cardiovascular variability during sleep-wake transitions of adult male Wistar-Kyoto rats on their normal daytime sleep were analyzed. INTERVENTIONS: A 6-h daytime sleep-wakefulness recording session was performed. MEASUREMENTS AND RESULTS: Electroencephalogram and electromyogram (EMG) signals were subjected to continuous power spectral analysis, from which mean power frequency of the electroencephalogram (MPF) and power of the EMG were quantified. Active waking (AW), quiet sleep (QS), and paradoxical sleep (PS) were defined every 8 s according to corresponding MPF and EMG power. Continuous power spectral analysis of R-R intervals was performed to quantify its high-frequency power (HF, 0.6-2.4 Hz), low-frequency power (0.06-0.6 Hz) to HF ratio (LF/HF). MPF exhibited two phases of change during AW-QS and QS-AW transitions: a slowly changing first phase followed by a rapidly changing second phase. HF increased linearly with the decrease of MPF during the first phase of AW-QS transition whereas LF/HF increased linearly with the increase of MPF during the first phase of QS-AW transition. However, the LF/HF was not correlated with the HF. The MPF and HF exhibited only a rapidly changing phase during QS-PS transition. The LF/HF declined transiently during the QS-PS transition, followed by a sustained increase in PS. CONCLUSIONS: The parasympathetic activity before falling asleep and the sympathetic activity before waking up change coincidentally with EEG frequency, and may respectively contain the messages of sleeping and waking drives.     

EEG activity during the verbal-cognitive stage of motor skill acquisition

This study examined changes in EEG activity associated with motor performance during the verbal-cognitive stage of skill learning. Participants (n = 14) were required to practice a sequential finger tapping task. EEG activity was recorded both before and after short-term practice, during finger tapping and during two control conditions. EEG power (Fz, Cz, Pz, T3, T4) and coherence (T3-Fz, T4-Fz, Fz-Cz, Fz-Pz) were computed for the theta (4-8 Hz), slow alpha (8-10 Hz), fast alpha (10-12 Hz), slow beta (12-20 Hz), and fast beta (20-28 Hz) bandwidths. Changes in motor performance were rapid during the very early stages of practice and then slowed in accord with the law of practice. These changes were accompanied by increases of theta power at Fz and beta coherence at T4-Fz, suggesting that progression through the verbal-cognitive stage of a sequential finger tapping task is accompanied by more narrowed attention and improved mapping between the stimuli and the finger movements.     

Analysis of correlation between physical training and autonomic function by using multivariate analysis: establishing an indicator of health]

The purpose of this study is to assess the effects of physical training on autonomic nervous function. Twenty-two healthy subjects(12 males and 10 females) participated in this study. We inquired contents of the exercise for each subject. Continuous ECG was recorded during 320 seconds at supine resting. Respiratory rhythm was fixed at 0.25 Hz(15 time/min). On the basis of spectral analysis of heart rate variability, the autonomic nervous function was assessed by low frequency power(LF: 0.06-0.13 Hz) and high frequency power(HF: 0.16-0.50 Hz). The predominance of sympathetic nervous activity were indicated by the LF/HF and LF-HF. Relationship between physical training and autonomic function was analyzed by using multivariate analysis(partial correlation analysis). As the results, LF power and LF-HF negatively correlated with training time per day, energy expenditure per day, energy expenditure per week, and total energy expenditure, respectively(p < 0.05). HF power positively correlated with energy expenditure per day, energy expenditure per week, and total energy expenditure, respectively(p < 0.05). These results indicate not training time but energy expenditure alters the autonomic nervous function. This index may be useful for evaluating training effect on the promotion of health.     

Change in activity of the sympathetic nervous system in diet-induced obese rats

We investigated the change in activity of the sympathetic nervous system (SNS) in high-sucrose diet (HSD)-induced obese rats compared with controls. Power spectral analyses of R-R interval variability were performed to obtain the low frequency (LF, 0.04-0.699 Hz) and high frequency (HF, 0.7-3.0 Hz) powers. The percents of fat mass to body weight (%F/BW) and fat to muscle ratios (F/M) were significantly increased in HSD-fed rats. Plasma glucose, leptin, and triglyceride concentrations in rats fed with HSD were significantly increased. LF in normalized units (LFn), which represents both sympathetic and parasympathetic activities, was significantly increased whereas HF in normalized unit (HFn), which represents parasympathetic activity, was significantly decreased in HSD-fed rats. LF/HF, which represents sympathetic activity, was significantly increased in HSD-fed rats and was correlated with leptin (r=0.549, p<0.023), %F/BW (r=0.513, p<0.035), F/M (r=0.536, p<0.038), and triglyceride (r=0.497, p<0.042). When adjusted for leptin concentrations, however, LF/HF of HSD-fed rats was significantly decreased. In conclusion, HSD-induced obese rats showed increased LF/HF, which was significantly decreased by adjustment for leptin concentrations. We suggest that stimulating effect of leptin on SNS is reduced, which might play a role in induction of obesity by HSD.     

The autonomic nervous activity of hypertension

Autonomic nervous function was evaluated by means of power spectral analysis of heart rate variability in hospitalized patients with different circadian blood pressure(BP) variation, i.e., dipper(n = 33), non-dipper(n = 37), extreme dipper(n = 26) and riser(n = 20). Ambulatory BP monitoring was performed by A & D TM2425 based on a cuff-oscillometric method. Circadian BP variation was defined in these subjects. The non-dipper, extreme dipper and riser subjects were defined as those whose nocturnal decrease in systolic BP was less than 10%, more than 20% and elevation of BP, as compared to the daytime BP, respectively. Power spectral analysis of hourly R-R intervals for 24 hours was done to obtain the low frequency power(LF, 0.04 to 0.15 Hz) and high frequency power(HF, 0.15 to 0.40 Hz). LF/HF ratio was considered to be an index of sympathetic nervous activity, and HF parasympathetic nervous activity, respectively. LF/HF was significantly lower in both riser and non-dipper than that in dipper subjects throughout the day. In non-dipper day-night difference of HF was smaller than in dipper and extreme dipper groups. These findings indicated that riser and non-dipper hypertensives were characterized by decreased physiological circadian fluctuation of autonomic functions when compared to dipper subjects. The circadian variation of BP may be mediated at least in part by circadian variation of autonomic nervous system activity.     

咖啡摄入前后心率变异性的对比研究

目的研究中等剂量咖啡摄入对青年受试者心率变异性的影响,明确咖啡对心脏自主神经活性的作用。方法无咖啡因摄入习惯的16名健康青年受试者(身高167 cm±7.2 cm、体重61.3 kg±6.3kg、年龄24.9岁±2.8岁)参与本项研究,在摄入含6 mg/kg咖啡因的咖啡饮品后,于8:40~10:45应用动态心电图记录仪(Holter)进行咖啡摄入前后心电信号的采集及心率(heart rate,HR)和心率变异性指标的分析。心率变异性指标包括R-R间期标准差(SDNN)、相邻R-R间期差值的均方根值(r MSSD)、相邻的R-R间期之差大于50 ms的心搏数占总心搏数的百分比(PNN50)、标化低频(normalized low frequency power,LFnorm)、标化高频(normalized high frequency power,HFnorm)、低频功率(low frequency,LF)与高频功率(high frequency,HF)的比值(LF/HF)。结果饮用咖啡后,心率、心率变异性指标均发生改变且具有统计学意义,HR、LFnorm和LF/HF分别降低了7.5%、17%和35%。r MSSD、PNN50和HFnorm分别提高了82%、80%和58%。其中HR及LF/HF随着时间的变化趋势最明显。HRV参数在饮用咖啡前后的差值ΔLF与ΔHF,ΔLF与ΔLF/HF均显著相关,相关系数为-0.980和0.903。结论中等剂量咖啡可引起心率变异性的改变和心率的降低,抑制交感神经活性,提高副交感神经活性。     

基于遥测技术的大鼠24小时心率变异性分析

本研究应用遥测技术连续记录大鼠在无束缚条件下24h心电信号，并通过心率变异性（Heart rate variability，HRV）频谱分析的方法研究大鼠24h自主神经活动。大鼠24hHRV分析结果表明：自主神经活动具有明显昼夜节律，在睡眠期迷走神经活动较活跃，而在清醒期以交感神经活动为主；HRV频谱中低频和高频成分的比值（LF／HF）随着睡眠深度的变化而波动。24hHRV分析可以获得自主神经系统活动的丰富信息，并有助于研究自主神经系统在生理和病理过程中的调控作用。     

Effect of magnitopuncture on sympathetic and parasympathetic nerve activities in healthy drivers--assessment by power spectrum analysis of heart rate variability

The object of this study was to assess the effects of magnitopuncture applied to Dazhui (DU14) point and Neiguan (PC6) points on sympathetic and parasympathetic nerve activities by power spectrum analysis of heart rate variability in healthy drivers during simulated driving. Using power spectrum analysis, the low frequency (LF) and high frequency (HF) components of heart rate variability can be calculated reflecting the sympathetic and parasympathetic activity. The 40 healthy male subjects were randomly divided into two groups: A (study group) and B (control group). All subjects were required to be well rested before the experiment. The subjects of both groups were required to perform a simulated driving task for 3 h. During the driving, magnitopunctures were applied to the DU14 and PC6 points for A while the subject performed the task for 2.5 h, and for B magnitopunctures were applied to non-acupuncture points which were 1.5 cm away from the two acupuncture points respectively over the same time. Subjective response to a questionnaire was obtained after the simulated task in the two groups. At the end of the driving task the LF component in normalized units (NU) had decreased significantly (P<0.05) indicating a reduced sympathetic nerve activity and the HF component (NU) increased significantly (P<0.05) indicating a increased parasympathetic nerve activity for A compared with pre-stimulation while for B no significant differences were observed. There were significant group differences in LF (NU), HF (NU) and LF:HF at the end of the driving task (P<0.05). It was concluded that a modulating effect of magnitopuncture on sympathetic and parasympathetic nerve activities in healthy subjects was associated with the acupuncture points. The findings represent physiological evidence that magnitopuncture may reduce mental fatigue in healthy drivers. Electronic Publication     

Features of autonomic cardiovascular control during cognition in major depressive disorder

Previous research has suggested reduced parasympathetic cardiac regulation during cognitive activity in major depressive disorder (MDD). However, little is known about possible abnormalities in sympathetic control and cardiovascular reactivity. This study aimed to provide a comprehensive analysis of autonomic cardiovascular control in the context of executive functions in MDD. Thirty six MDD patients and 39 healthy controls participated. Parameters of sympathetic (pre‐ejection period, PEP) and parasympathetic control (high and low frequency heart rate variability, HF HRV, LF HRV; and baroreflex sensitivity, BRS) as well as RR interval were obtained at rest and during performance of executive function tasks (number‐letter task, n‐back task, continuous performance test, and Stroop task). Patients, as compared to controls, exhibited lower HF HRV and LF HRV during task execution and smaller shortenings in PEP and RR interval between baseline and tasks. They displayed longer reaction times during all conditions of the tasks and more omission errors and false alarms on the continuous performance test. In the total sample, on‐task HF HRV, LF HRV and BRS, and reactivity in HF HRV, LF HRV, and PEP, were positively associated with task performance. As performance reduction arose independent of executive function load of the tasks, the behavioral results reflect impairments in attention and processing speed rather than executive dysfunctions in MDD. Abnormalities in cardiovascular control during cognition in MDD appear to involve both divisions of the autonomic nervous system. Low tonic parasympathetic control and blunted sympathetic reactivity imply reduced physiological adjustment resources and, by extension, provide suboptimal conditions for cognitive performance.     

Autonomic activity during human sleep as a function of time and sleep stage

While there is a developing understanding of the influence of sleep on cardiovascular autonomic activity in humans, there remain unresolved issues. In particular, the effect of time within the sleep period, independent of sleep stage, has not been investigated. Further, the influence of sleep on central sympathetic nervous system (SNS) activity is uncertain because results using the major method applicable to humans, the low frequency (LF) component of heart rate variability (HRV), have been contradictory, and because the method itself is open to criticism. Sleep and cardiac activity were measured in 14 young healthy subjects on three nights. Data was analysed in 2-min epochs. All epochs meeting specified criteria were identified, beginning 2 h before, until 7 h after, sleep onset. Epoch values were allocated to 30-min bins and during sleep were also classified into stage 2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. The measures of cardiac activity were heart rate (HR), blood pressure (BP), high frequency (HF) and LF components of HRV and pre-ejection period (PEP). During non-rapid eye movement (NREM) sleep autonomic balance shifted from sympathetic to parasympathetic dominance, although this appeared to be more because of a shift in parasympathetic nervous system (PNS) activity. Autonomic balance during REM was in general similar to wakefulness. For BP and the HF and LF components the change occurred abruptly at sleep onset and was then constant over time within each stage of sleep, indicating that any change in autonomic balance over the sleep period is a consequence of the changing distribution of sleep stages. Two variables, HR and PEP, did show time effects reflecting a circadian influence over HR and perhaps time asleep affecting PEP. While both the LF component and PEP showed changes consistent with reduced sympathetic tone during sleep, their pattern of change over time differed.     

Cardiac autonomic profile during rest and working memory load in essential hypotensive women

To our knowledge, no previous study has provided reliable data supporting a different modulation of the Neurovegetative system in essential hypotension. Our purpose was to provide, in essential hypotensive women compared to normotensives, evidence of a distinct sympathetic and parasympathetic cardiac control. Cardiovascular and autonomic indexes derived by impedance cardiography (heart rate, HR; pre-ejection period, PEP), photoplethysmographic technique (blood pressure, BP) and heart rate variability analysis (high and low frequencies power, HF and LF) were continuously collected during rest and mental stress condition. Hypotensives, compared to normotensives, exhibited prolonged PEP (low sympathetic tone) and elevated HF (high vagal involvement) during rest. In addition, they showed cardiovascular (reduced increases in BP and HR) and sympathetic (lower reductions of PEP) hypo-reactivity to the task. Furthermore, a lower sympathetic reactivity in hypotensives was associated to a poorer task performance. Essential hypotension was characterized by a low sympathetic and high parasympathetic tone. In addition, a reduced sympathetic nervous system reactivity suggests the main role of the Neurovegetative system in mediating the relationship between blood pressure and cognitive performance in hypotensives.     

Cardiovascular effects of morning nutrition in preadolescents

The cardiovascular response to eating has been extensively investigated in adults, but comparable data in children are lacking. In this investigation, heart-rate and heart-rate variability were evaluated in preadolescents during resting periods in the morning initially while participants maintained overnight fasting, and again after the participants either ate a standardized breakfast or continued fasting. Relative to the initial fasting period, heart rate (HR) increased slightly in fed participants and decreased significantly in those who continued to fast. These effects were associated with significant increases in low- (LF: 0.04-0.15 Hz; primarily sympathetic influences) and high-frequency (HF:0.15-0.5 Hz; parasympathetic influences) spectral components in fasting participants and with nonsignificant decreases in both components in fed participants. Although these HF changes are consistent with the observed heart-rate variations (i.e., increases and decreases in parasympathetic influence associated with decreased and increased HR, respectively), the LF increase with the slowing, and decrease with the acceleration of HR run counter to expected sympathetic effects on HR. The net effect of these modulations was unchanged sympathovagal balance (LF/HF) for fasting participants but a significant decrease for fed participants across recording periods. The results indicate that the continuation of overnight fasting is associated with a significant increase in parasympathetic activity that is attenuated by eating breakfast. Furthermore, the findings suggest that the parasympathetic contribution to the LF spectral component is significantly enhanced in preadolescents, and, consequently, the LF/HF ratio-generally considered to reflect sympathovagal balance-does not segregate sympathetic and parasympathetic influences in children.     

The Autonomic Nervous Activity in Patients with Essential Hypertension who Showed Early Morning Rise of Blood Pressure

Autonomic nervous function was evaluated by means of power spectral analysis of heart rate variability in patients with essential hypertension who showed early morning rise of blood pressure (BP). We monitored ambulatory (BP) and physical activity in 80 untreated patients using TM 2425 (A&D Co.Ltd.). Early morning rise of BP was defined a patient's blood pressure obtained between 6:00 to 9:00am is 170mmHg or higher. Patients who showed early morning rise of BP were categorized into groups. Twenty patients, whose mean BP obtained between 6:00 to 9:00am were higher than those obtained between 3:00 to 600am by 30mmHg or more, were defined as a surge type. Sixty patients, in whom the difference in BP was less than 30mmHg, were defined as a sustained type. Power spectral analysis of hourly R-R intervals for 24 hours was performed to obtain the low frequency power (LF, 0.04 to 0.15 Hz) and high frequency power (HF, 0.15 to0.04 Hz). LFn and LF/HF ratio were considered to be indexes of sympathetic nervous activity, and HF parasympathetic nervous activity, respectively. Between 3:00 to 6:00am, LFn and LF/HF were significantly higher and HF was significantly lower in the sustained type patients than in the surge type patients. LF/HF and LFn in the surge type elevated significantly beween 6:00 to 9:00am. These results indicate that both the loss of nocturnal decline in BP in the sustained type and the morning rise in BP in the surge type to occurred in association with changes in autonomic nervous system.