Abstract
This study aimed to clarify the physiological effects of touching hinoki cypress (hereinafter called “hinoki”) (Chamaecyparis obtusa) wood with the palm of the right hand on brain activity and autonomic nervous activity. Twenty-two female university students (mean age 21.1 ± 0.2 years) participated in the study. As an indicator of brain activity, oxyhemoglobin (oxy-Hb) concentrations were measured in the left/right prefrontal cortex using near-infrared time-resolved spectroscopy. Heart rate variability (HRV) was used as an indicator of autonomic nervous activity. The high-frequency (HF) component of HRV, which reflected parasympathetic nervous activity, and the low-frequency (LF)/HF ratio, which reflected sympathetic nervous activity, were measured. Plate (300 × 300 mm) of uncoated hinoki was used as tactile stimulation. Marble was used as a control material. After sitting at rest with their eyes closed, the participants touched the materials for 90 s with their eyes still closed. The results showed that tactile stimulation with hinoki significantly decreased oxy-Hb concentration in the left prefrontal cortex and increased ln(HF) reflected parasympathetic nervous activity compared with marble. In conclusion, our study showed that touching hinoki wood with the palm calms prefrontal cortex activity and increases parasympathetic nervous activity, thereby inducing physiological relaxation.
Highlights
The stress that modern society brings on humans, especially “technostress [1],” is known to cause an increase in stress conditions [2]
The results indicated that touching uncoated white oak wood with the palm calmed prefrontal cortex activity [17, 18], increased parasympathetic nervous activity [17, 18], and decreased heart rate [18] more than did various building materials [17] and coated wood materials [18], thereby inducing physiological relaxation
Data are expressed as means ± standard error, n = 22, †p < 0.05, *p < 0.05 as determined by the paired t test; the Holm correction was applied concentration was − 0.36 ± 0.08 μM during contact with hinoki and − 0.04 ± 0.11 μM during contact with marble; analysis of the difference indicated that the oxy-Hb concentration was significantly decreased after touching hinoki compared with marble (Fig. 4a, p < 0.05)
Summary
The stress that modern society brings on humans, especially “technostress [1],” is known to cause an increase in stress conditions [2]. Natural material that is used in houses and furniture, and it is empirically known to have a relaxing effect on humans [6]. A review outlining the current state of research regarding the physiological effects of wood-derived stimulation on humans [6] reported that data on the physiological effects of olfactory stimulation have continued to accumulate, following the development of physiological measurement technology in recent years. The physiological relaxation effects of stimulation by olfactory stimuli such as air-dried hinoki cypress (hereinafter called “hinoki”) (Chamaecyparis obtusa) wood chips [8], α-pinene [9], and D-limonene [10], which are components derived from wood, have been reported. Several studies on visual stimulation have been conducted using
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