Physiological effect of olfactory stimulation by Hinoki cypress Chamaecyparis obtusa leaf oilReport as inadecuate

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Journal of Physiological Anthropology

, 34:44

First Online: 22 December 2015Received: 13 August 2015Accepted: 15 December 2015


BackgroundIn recent years, increasing attention has been paid to the physiological effects of nature-derived stimulation. The physiological relaxation effects caused by forest-derived olfactory stimuli have been demonstrated. However, there are no studies on the physiological effects of olfactory stimuli by Hinoki cypress Chamaecyparis obtusa leaves. We investigated the effects of olfactory stimulation by Hinoki cypress leaf oil on the left-right prefrontal cortex activity, assessed using near-infrared time-resolved spectroscopy TRS, and on the autonomic nervous activity, assessed by measuring heart rate variability HRV.

MethodThirteen female university students mean age, 21.5 ± 1.0 years participated in the study. Physiological measurements were performed in an artificial climate maintained at 25 °C, 50 % relative humidity, and 230-lx illumination. Hinoki cypress leaf oil was used as an olfactory stimulation with air as the control. The odor was administered for 90 s, while the subjects sat with their eyes closed. Oxyhemoglobin oxy-Hb concentrations were measured in the prefrontal cortex using TRS. The high-frequency HF component of HRV, which is an estimate of parasympathetic nervous activity, and the low-frequency LF-LF + HF ratio, which is an estimate of sympathetic nervous activity, were measured by electrocardiography. A modified semantic differential method was used to perform subjective evaluations.

ResultsOlfactory stimulation by Hinoki cypress leaf oil induced a significant reduction in oxy-Hb concentration in the right prefrontal cortex and increased parasympathetic nervous activity. The subjects reported feeling more comfortable.

ConclusionThese findings indicate that olfactory stimulation by Hinoki cypress leaf oil induces physiological relaxation.

KeywordsJapanese cypress Leaf oil Odor Physiological relaxation Prefrontal activity Near-infrared spectroscopy Autonomic nerve activity Heart rate variability Semantic differential method AbbreviationsHFhigh frequency

HRVheart rate variability

LFlow frequency


SDsemantic differential

TRSnear-infrared time-resolved spectroscopy

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Author: Harumi Ikei - Chorong Song - Yoshifumi Miyazaki



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