Exposure to natural sounds is known to induce feelings of relaxation; however, only few studies have provided scientific evidence on its physiological effects. This study examined prefrontal cortex and autonomic nervous activities in response to forest sound. A total of 29 female university students (mean age 22.3 ± 2.1 years) were exposed to high-resolution sounds of a forest or city for 60 s, using headphones. Oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex were determined by near-infrared spectroscopy. Heart rate, the high-frequency component of heart rate variability (which reflects parasympathetic nervous activity), and the ratio of low-frequency to high-frequency (LF/HF) components (which reflects sympathetic nervous activity) were measured. Subjective evaluation was performed using the modified semantic differential method and profiles of mood states. Exposure to the forest sound resulted in the following significant differences compared with exposure to city sound: decreased oxy-Hb concentrations in the right prefrontal cortex; decreased ln(LF/HF); decreased heart rate; improved feelings described as “comfortable,’’ “relaxed,” and “natural”; and improved mood states. The findings of this study demonstrated that forest-derived auditory stimulation induced physiological and psychological relaxation effects.

Heart rate variability (HRV), a non-invasive index of autonomic controls of the heart, has extensively been employed in various fields of study. The application range of this index persists to expand over the research horizon, and the need continues to demand technical complements for hitherto known deficiencies. Concurrent technical advances in recent years have yielded methodological techniques capable of performing quantitative analysis of HRV. However, as various approaches designed for HRV analysis exist, quantitative comparisons of the investigations have become difficult. Current physiological interpretations of the components of HRV are also inconsistent. Moreover, the issue of respiratory control has been much disputed when determining the HRV. In an attempt to clarify the current controversial state in HRV measurement, the present paper, based on the physiological background of HRV, pursued various procedures of HRV measurement and furnished global explanations for special features characterizing the various analytical approaches adopted thereof.

The present study aimed to evaluate the effect of walking in forest environments on autonomic nervous activity with special reference to its distribution characteristics. Heart rate variability (HRV) of 485 male participants while walking for ~15 min in a forest and an urban area was analyzed. The experimental sites were 57 forests and 57 urban areas across Japan. Parasympathetic and sympathetic indicators [lnHF and ln(LF/HF), respectively] of HRV were calculated based on ~15-min heart rate recordings. Skewness and kurtosis of the distributions of lnHF and ln(LF/HF) were almost the same between the two environments, although the means and medians of the indicators differed significantly. Percentages of positive responders [presenting an increase in lnHF or a decrease in ln(LF/HF) in forest environments] were 65.2 and 67.0%, respectively. The percentage of lnHF was significantly smaller than our previous results on HRV during the viewing of urban or forest landscapes, whereas the percentage of ln(LF/HF) was not significantly different. The results suggest that walking in a forest environment has a different effect on autonomic nervous activity than viewing a forest landscape.

The gait of a healthy person is believed to be more regular and symmetrical than those of an individual with a disease. Thus, symmetry and regularity are important indicators of human gait.

This study aimed to present normative reference values of heart rate variability and salivary alpha-amylase in a healthy young male population with a particular focus on their distribution and reproducibility.

The present study was designed to examine the effects of illuminance and color temperature of room lighting. Four male students volunteered as subjects. Each of them performed a calculation task for 95 minutes under nine different lighting environments consisting of a combination of three levels of illuminance (320lx, 1000lx and 2000lx) and three levels of color temperature (3000 degrees K, 5000 degrees K and 7500 degrees K). Three types of fluorescent lamps were used as a light source to vary the color temperature. Blood pressure, critical flicker frequency (CFF) and accommodation time of eye movements were measured every 30 minutes during the task. The accommodation time was significantly influenced by the illuminance level and both the relaxation time and contraction time were prolonged under 2000lx. The diastolic blood pressure was significantly affected by the color temperature level and increased under 7500 degrees K. As for the CFF, the interaction between illuminance and color temperature was significant. These results mean that not only the illuminance but also color temperature produces physiological effects. The present study may be the first to recognize the effect of color temperature on the blood pressure.