Shinji Miyake

Power Spectral Analysis of Heart Rate Variability in Healthy Young Women During the Normal Menstrual Cycle

This study investigated the fluctuations of autonomic nervous activities during the menstrual cycle.Twenty college females were tested for cardiovascular reactivity to mental challenge during both follicular and luteal phases across two menstrual cycles. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. At baseline, although heart rate and blood pressure did not differ across the menstrual cycle, the low-frequency (LF) component in the HRV was higher and the high-frequency (HF) component in the HRV was lower during the luteal phase than during the follicular phase. The LF/HF ratio was also significantly greater in the luteal phase. These data suggest that sympathetic nervous activities are predominant in the luteal phase as compared with follicular phase. In addition, the power spectral analysis of HRV has more sensitivity than heart rate or blood pressure in assessing the slight fluctuations of autonomic nervous activities during the menstrual cycle.

Multivariate workload evaluation combining physiological and subjective measures

This paper suggests a way to integrate different parameters into one index and results obtained by a newly developed index. The multivariate workload evaluation index, which integrates physiological parameters and one subjective parameter through Principle Components Analysis, was proposed to characterize task specific responses and individual differences in response patterns to mental tasks. Three different types of mental tasks were performed by 12 male participants. Heart rate variability, finger plethysmogram amplitude, and perspiration were used as physiological parameters. Three subscales, mental demand, temporal demand and effort out of six subscales in the NASA-Task Load Index were used as subjective scores. These parameters were standardized within each participant and then combined. It was possible to assess workload using this method from two different aspects, i.e. physiological and subjective, simultaneously.

Power spectral analysis of heart rate variability in Type As and Type Bs during mental workload.

&NA; Recently several studies have suggested that there are differences in autonomic balance between Type As and Type Bs. This study evaluates a sympathovagal interaction in Type A (n = 8) and Type B (n = 11) male students during a mental arithmetic task by power spectral analysis of heart rate variability. The low‐frequency component to high‐frequency component ratio was significantly greater in Type As than in Type Bs during a resting period. No significant differences were found in heart rate changes and blood pressure between the two kinds of subject groups. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Bs. Type As showed dominant sympathetic activity.

Assessment of autonomic function in traumatic quadriplegic and paraplegic patients by spectral analysis of heart rate variability

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart rate variability (HRV) of quadriplegic and paraplegic male subjects at rest in the supine position. In agreement with our previous study, in nine of 15 quadriplegic patients only the high-frequency (HF: center frequency = respiratory frequency) component (a marker of vagal modulation of heart rate) was observed. In contrast, in six of the quadriplegic patients both the HF component and the low-frequency (LF: center frequency at approx. 0.1 Hz, 0.03-0.15 Hz in this study) component (a marker of sympathetic and vagal modulation of heart rate) were observed. However, in six quadriplegic patients who presented the LF component, (i) the center frequency of the LF component was lower than that in 10 healthy, sedentary, age-matched males (control I) (P < 0.01), (ii) the power of the HF component was smaller than that in the control-I group (P < 0.01) and (iii) the LF/HF power ratio (an index of sympathovagal balance) was larger than that in the control-I group (P < 0.05). On the other hand, in nine paraplegic patients with an intact 1st-4th thoracic spinal cord, from which the cardiac sympathetic nerves originate, the total power, the power of the LF component and that of the HF component were smaller than those in nine healthy, sedentary, age-matched males (control II) (P < 0.05, P < 0.01 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological responses to workload change. A test/retest examination.

The purpose of this study is to examine the test/retest consistency of physiological responses induced by mental tasks. Fifteen healthy male university students were recruited as participants. They were instructed to perform a 5-min Multi-Attribute Task Battery (MATB) trial three times successively. The task difficulty level of the tracking task of the second trial was set as medium (M). The first one was set as more difficult (H) and the last trial was easiest (L). The difficulty levels of the other two tasks (resource management and system monitoring) of the MATB were identical for all three trials. The participants repeated this procedure on three different days separated by at least a 1-day interval. The order of the tasks was the same for all repeated trials, i.e., H-M-L. Tissue blood volume from the tip of the nose using a laser Doppler blood flow meter, skin potential level (SPL), ECG from three leads on the chest, systolic time intervals (pre-ejection period, left ventricular ejection time), and hemodynamic parameters (stroke volume, cardiac output) were recorded during the task trials and before and after 5-min resting periods. The participants reported their subjective workload via NASA-TLX after each task trial. Autonomic nervous system parameters derived from the above-mentioned signals, subjective workload scores, and performance indices of MATB were analyzed, and test/retest reliability was investigated. The results showed that a significant test/retest correlation was obtained for SPL for more participants than in the other parameters, although there were large individual differences.

Power spectral analysis of heart rate variability in type A females during a psychomotor task

This study investigated changes in autonomic nervous activities due to psychological stress in Type A females. Eight Type A and eight Type B females performed a psychomotor task for 30 minutes. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. Results showed the low frequency (LF) component and LF/HF ratio in Type A females increased after the onset of the task. There were no significant differences in task performance between Type A and Type B females. The subjective mental workload increased gradually in Type A females during the tasks, whereas in Type B females this parameter did not change in a consistent manner. The results suggest that the sympathetic nervous system in Type A females was more stimulated by the task and Type A females felt a greater subjective mental workload than did Type B females.

Assessment of autonomic function in myotonic dystrophy by spectral analysis of heart-rate variability

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart-rate variability (HRV) of 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and sex-matched healthy, sedentary humans (control) at rest in the supine position. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead electrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency component (a marker of sympathetic and vagal modulation of heart rate) and that of the high-frequency component (a marker of vagal modulation of heart rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest that the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform daily activities. Therefore, one must give careful consideration to the cardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.

POWER SPECTRAL ANALYSIS OF HEART RATE VARIABILITY IN TYPE As DURING SOLO AND COMPETITIVE MENTAL ARITHMETIC TASK

It has been reported that there are differences in autonomic balance between Type As and Type Bs. This study evaluated the sympathovagal interaction in Type A (N = 10) and Type B (N = 10) male students during mental arithmetic task in a solo and a competitive condition by the spectral component analysis of heart rate variability (HRV). The low-frequency (LF) component to high-frequency (HF) component ratio was significantly greater in Type As than in Type Bs, though no significant differences were found in task performance, heart rate change, and blood pressure between the two subject groups in both conditions. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Type Bs, and that Type As showed dominant sympathetic activity. The results suggest that the power spectral analysis of HRV, which is convenient and non-invasive, has enough sensitivity to discriminate differences in autonomic balance between Type A subjects and Type B subjects, not only during the solo and competitive task period but also during the resting period.

Speech perception in noise when wearing hearing protectors with little low-frequency attenuation

In industrial workplaces, it is widely believed that the use of hearing protectors interferes with communication and with the perception of warming signals. The objective of this study was to estimate effects of attenuation of the protectors on speech perception in noise. In the experiment, the intelligibility of monosyllables was assessed for ten normal-hearing adults, using three types of protectors with different attenuation characteristics. The speech materials were presented at two speech levels (65 and 85 dBA) in noise. The noise level was altered at signal-to-noise ratios (SNR) of 0, +5, and +10 dB. The results showed that speech intelligibility was significantly influenced by type of protector, speech level, and SNR. The interaction between these factors was statistically significant. The wearing of the earplug with decreased low-frequency attenuation resulted in less deterioration when the speech was presented at 65 dBA. On the other hand, such an earplug did not improve speech intelligibly as compared with other protectors when the speech was presented at 85 dBA. Therefore, the use of the protectors with decreased attenuation to improve speech communication for workers wearing protectors needs to be re-examined.

Recovery patterns in the physiological responses of the autonomic nervous system induced by mental workload

It is widely understood that mental stress produces various physiological changes. Though the relationship between mental stress and physiological feedback has been extensively reported, few reports have tried to clarify the relationships between physiological responses and the intensity level or type of stress. In this study, we investigated autonomic nervous system activities to find a physiological index based on which we can evaluate the intensity of mental stress. As a result, we found that some physiological indexes acquire certain characteristics during the recovery process, and we consider that these indexes might be related to the intensity of mental stress.