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Physiological effects of visual, olfactory, auditory, and tactile factors of forest environments

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Abstract

The forest environment affects humans via the five senses, providing stimulation of various kinds such as scenery, the smell of wood, the sound of streams or the rustle of leaves, and the feel of the surface of trees and leaves. Many laboratory experiments have been conducted to elucidate the physiological effects of sensory inputs in forest environments. In this chapter, we will initially examine some non-invasive physiological methods that can be applied in a laboratory study to assess physiological changes. Recent progress in technology has enabled the precise non-invasive investigation of physiological responses. Various measurement methods will be shown for each physiological function. We will then provide an overview of studies on the effects of certain elements of the forest environment within a laboratory setting. Studies have revealed that the components of a forest environment, even if as components of stimulation, may have a positive effect on human physiology.

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... Several studies have focused on olfactory stimulation with Japanese cedar (Cryptomeria japonica), a common and familiar coniferous tree in Japan. Tsunetsugu et al. [38] revealed the effects of olfactory stimulation by Japanese cedar wood chips on the prefrontal cortex activity and blood pressure of 14 male university students. The participants were seated in an indoor artificial climate chamber with the temperature, humidity, and illuminance set at 25°C, 60%, and 50 lx, respectively. ...
... Single substance inhalation experiments using the main volatile components of wood such as a-pinene and limonene have also been conducted following the same experimental design as in the reports already described [38,45,46]. Tsunetsugu et al. [38] investigated the effects of olfactory stimulation by a-pinene and limonene on blood pressure. ...
... Single substance inhalation experiments using the main volatile components of wood such as a-pinene and limonene have also been conducted following the same experimental design as in the reports already described [38,45,46]. Tsunetsugu et al. [38] investigated the effects of olfactory stimulation by a-pinene and limonene on blood pressure. The strength of perceptibility of the stimulus was adjusted to ''slightly sensed'' on average, and the blood pressure of the participants was measured every second throughout the 90-s duration of stimulation. ...
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It is empirically known that wood can cause a comfort enhancement effect in humans. On the other hand, not enough scientific knowledge based on evidence-based research is available on this subject. However, data using physiological indices have increasingly accumulated in recent years. This review provides an overview of the current situation for peer-reviewed reports related to the physiological effects of wood. We reviewed reports that elucidated the effects of wood-derived stimulations on the olfactory, visual, auditory, and tactile sensations using physiological indices such as brain activity (e.g., near-infrared spectroscopy) and autonomic nervous activity (e.g., heart rate variability and blood pressure). It became clear that many studies were limited by (1) a small number of participants, mostly aged in their 20s; (2) use of only a single stimulus (e.g., only olfactory or only visual), or (3) an incomplete experimental design. In addition, this review examined the field of forest therapy, for which there is abundant research. Further study is needed to elucidate the physiological effects of wood on humans.
... Wood has been used as building material and for making furniture since a long time, and it has been known from experience that woody smell acts as a mood relaxant. Several studies on the physiological and psychological effects of wood or wood-derived smells have been conducted [1][2][3][4][5][6][7]. The inhalation of air containing volatile organic compounds released from the interior walls of Japanese cedar suppresses increases in salivary chromogranin A [1]. Olfactory stimulation by Japanese cedar chips decreases systolic blood pressure and prefrontal cortex activity [2]. ...
... Several studies on the physiological and psychological effects of wood or wood-derived smells have been conducted [1][2][3][4][5][6][7]. The inhalation of air containing volatile organic compounds released from the interior walls of Japanese cedar suppresses increases in salivary chromogranin A [1]. Olfactory stimulation by Japanese cedar chips decreases systolic blood pressure and prefrontal cortex activity [2]. Olfactory stimulation by air-dried wood chips of Japanese cypress, which is commonly found and is widely used as a building material in Japan, reduced the oxygenated hemoglobin concentration in the prefrontal cortex [3]. ...
... Wood is a familiar natural material because it is globally used as a building material or for making furniture. In recent years, the accumulation of data on the physiological effects of wood or wood-derived stimuli, such as smell [1][2][3][4][5][6][7]12], viewing [20][21][22], and touch [23], has been promoted. In this study, we clarified the physiological relaxation effects of olfactory stimulation by a-pinene. ...
... The physiological effects experienced through each sense should be determined. The physiological effects of olfactory stimuli caused by forests or wood have been demonstrated [13][14][15][16][17][18]. Olfactory stimuli of air-dried wood chips of Hinoki cypress, which is a typical tree of Japan, have been shown to reduce oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex [13]. ...
... Olfactory stimuli of air-dried wood chips of Hinoki cypress, which is a typical tree of Japan, have been shown to reduce oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex [13]. Moreover, Japanese cedar chips have been shown to decrease systolic blood pressure and prefrontal cortex activity [14]. In addition, it has been reported that inhalation of cedrol, which is a compound that occurs in cedar extract, induced parasympathetic nervous activity and reduced sympathetic nervous activity [15]. ...
... In addition, it has been reported that inhalation of cedrol, which is a compound that occurs in cedar extract, induced parasympathetic nervous activity and reduced sympathetic nervous activity [15]. Inhalation of αpinene and limonene, which are major components of wood odor, decreased systolic blood pressure [14], and D-limonene enhanced activity of the parasympathetic nervous system and decreased heart rate [16]. A negative correlation between a subjects' heart rate and their subjective feeling of pleasantness after olfactory stimulation by six essential oil components, including pyridine, L-menthol, and 1,8-cineole, has also been demonstrated [17]. ...
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Background In 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). Method Thirteen 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. Results Olfactory 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. Conclusion These findings indicate that olfactory stimulation by Hinoki cypress leaf oil induces physiological relaxation.
... Recent studies have focused on the physiological relaxing effects of nature-derived stimulation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], and there are several reports on the effects of wood odor on humans [9][10][11]. Miyazaki et al. [9] reported that inhalation of Taiwan hinoki oil odor decreases systolic blood pressure. ...
... Recent studies have focused on the physiological relaxing effects of nature-derived stimulation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], and there are several reports on the effects of wood odor on humans [9][10][11]. Miyazaki et al. [9] reported that inhalation of Taiwan hinoki oil odor decreases systolic blood pressure. ...
... Miyazaki et al. [9] reported that inhalation of Taiwan hinoki oil odor decreases systolic blood pressure. In addition, Tsunetsugu et al. [10] found that the odor of Japanese cedar chips decreases systolic blood pressure and prefrontal cortex activity and that inhalation of a-pinene and limonene, which are major components of the wood odor, also decreases systolic blood pressure. Joung et al. [11] reported that inhalation of D-limonene enhances activity of the parasympathetic nervous system and decreases heart rate. ...
... Many people are thus attracted to the physiological and psychological relaxing effect of exposure to nature. Field experiments on forest bathing [2][3][4][5][6][7][8][9][10], urban parks [11] and rooftop gardens [12] have demonstrated physiological relaxing effects of contact with nature. Furthermore, Li et al. reported forest bathing increased natural killer cell function and improved immune function [13]. ...
... Therefore, because many office workers work in highly stressful environments, it might be argued that alleviating this situation is matter of urgency. However, most previous studies [2][3][4][5][6][7][8][9][10] had male college students as subjects, and there are few studies of office workers aged 20 to 50 years. ...
... In the present study, we evaluated changes in autonomic nervous system activity, a physiological measure of stress, in office workers while viewing common fresh roses [19]. A relatively brief (4-minute) viewing session resulted in significantly increased parasympathetic nervous activity, concordant with several previous studies demonstrating enhanced parasympathetic activity while viewing a forest scene [2,3,6,7,9]. Furthermore, this result is consistent with our previous report demonstrating calming effects of roses in middle-aged and elderly medical staff [25] and in high-school students [26]. ...
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In recent years, the physiological relaxing effect brought by nature is becoming clear; however, many workers find it difficult to be exposed to nature in their working environment. Exposure to fresh flowers represents an opportunity to incorporate nature into their working lives. In this study, we examined the effects of exposure to roses on physiological and psychological variables (heart rate variability, pulse rate, and subjective responses) in office workers. The experimental site was Mizuho Information & Research Institute, Inc., in the Tokyo metropolitan area. Thirty-one male office workers were included in the present study. The subjects were exposed to thirty unscented pink roses (Rosa, Dekora) arranged in a cylindrical glass vase for 4 min. In the control condition, the subjects were not exposed to flowers. After the experiments, the subjects completed a questionnaire. The order of exposure was counterbalanced among subjects. Among subjects exposed to roses, the high-frequency component of heart rate variability was significantly higher than in controls. Similarly, 'comfortable,' 'relaxed' and 'natural' feelings were more common in subjects exposed to roses. Data from this study support the presence of physiological and psychological relaxing effects of being exposed to flowers on office workers.
... Other researchers asked subjects to do arithmetic in rooms with and without the smell of Japanese cedar, and they observed that during and after the completion of the arithmetic only in the room without the Japanese cedar smell, the ratio of the low-frequency (LF) component to the high-frequency (HF) component (LF/HF) of the subjects' heart rate variability (HRV) was increased, and their salivary alpha-amylase (SAA) levels were increased [6]. When people were exposed to Japanese cedar chips, their frontal activity was reduced and their blood pressure declined [9]. A later study described how the smell of wood suppressed the activities of the sympathetic nervous system and promoted the feeling of a 'natural' environment [10]. ...
... University, Fukuoka, Japan. 9 Faculty of Humanity-Oriented Science and Engineering, Kindai University, Iizuka, Japan. ...
Article
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Japanese cedar (Cryptomeria japonica) wood is widely used as a traditional construction material in Japan. The relationship between an individual's perceived comfort level and a preference for Japanese cedar wood interiors is of interest. We compared volunteers' physiological responses and subjective evaluations of wooden dwelling spaces with different wood materials: planed Japanese cedar lumber, or printed grain resin sheet overlay boards. Eighty-three subjects were asked to stay in each room for 30 min. We evaluated salivary stress markers, blood pressure, the profile of mood states-brief form (POMS), and a questionnaire that used the semantic differential method to evaluate the subjects' feeling state for both rooms. The concentrations of the volatile organic compounds in both rooms were also quantified after the experiment. The results demonstrated that the subjects' evaluation of each room was highly dependent on their preference; each room was evaluated more positively by subjects who preferred it. Although the subjects' feelings were also influenced by their preference, the room with Japanese cedar did not elicit negative feelings , even from the subjects who disliked it. The subjects' physiological responses were totally independent of their preferences. Their blood pressure decreased in the Japanese cedar room, and their salivary alpha-amylase activity was repressed in both rooms. These results indicated that the subjective evaluations were influenced in part by the sub-jects' preferences, while their physiological responses were not affected. Regardless of which room the subjects preferred , the Japanese cedar room reduced the subjects' blood pressure compared to the room with artificial materials.
... The strength of perceptibility of the stimulus was adjusted to a "weak smell", and the duration of the stimulation was approximately 60-90 s. The results showed a decreased systolic blood pressure and a calming effect on the prefrontal cortex activity in response to olfactory stimulation with cedar materials and cypress chips; therefore, this olfactory stimulation had an overall physiologically relaxing effect [55]. ...
... The blood pressure of the participants was measured every second throughout the 90 s duration of stimulation. The results showed that inhalation of α-pinene and limonene decreased systolic blood pressure [55]. Furthermore, increased parasympathetic nervous activity and decreased heart rate were also reported on olfactory stimulation with limonene [59]. ...
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Humans have evolved into what they are today after the passage of 6-7 million years. If we define the beginning of urbanization as the rise of the industrial revolution, less than 0.01% of our species’ history has been spent in modern surroundings. Humans have spent over 99.99% of their time living in the natural environment. The gap between the natural setting, for which our physiological functions are adapted, and the highly urbanized and artificial setting that we inhabit is a contributing cause of the “stress state” in modern people. In recent years, scientific evidence supporting the physiological effects of relaxation caused by natural stimuli has accumulated. This review aimed to objectively demonstrate the physiological effects of nature therapy. We have reviewed research in Japan related to the following: (1) the physiological effects of nature therapy, including those of forests, urban green space, plants, and wooden material and (2) the analyses of individual differences that arise therein. The search was conducted in the PubMed database using various keywords. We applied our inclusion/exclusion criteria and reviewed 52 articles. Scientific data assessing physiological indicators, such as brain activity, autonomic nervous activity, endocrine activity, and immune activity, are accumulating from field and laboratory experiments. We believe that nature therapy will play an increasingly important role in preventive medicine in the future.
... We have studied the effects of nature-derived stimulation, such as that of a forest [28][29][30][31][32][33][34][35][36], parks [37,38], a rooftop garden [39], flowers [40][41][42], foliage plants [43,44], and olfactory stimulation [45][46][47][48][49]. We observed that these natural environments and plants have physiological relaxation effects and can reduce stress states. ...
... Considerable attention is being paid to the effect of forest environment on humans. In addition to psychological indices, comprehensive evaluation using physiological indices has been performed for forests, indicating that the forest environment has relaxation effects [28,29,[32][33][34][35][36]. In contrast, with respect to gardening activity, many studies have reported the associated psychological effects [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. ...
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The relaxation effects of gardening have attracted attention; however, very few studies have researched its physiological effects on humans. This study aimed to clarify the physiological and psychological effects on high school students of viewing real and artificial pansies. Forty high school students (male: 19, female: 21) at Chiba Prefectural Kashiwanoha Senior High School, Japan, participated in this experiment. The subjects were presented with a visual stimulation of fresh yellow pansies (Viola x wittrockiana “Nature Clear Lemon”) in a planter for 3 min. Artificial yellow pansies in a planter were used as the control. Heart rate variability was used as a physiological measurement and the modified semantic differential method was used for subjective evaluation. Compared with artificial pansies, visual stimulation with real flowers resulted in a significant decrease in the ratio of low- to high-frequency heart rate variability component, which reflects sympathetic nerve activity. In contrast, high frequency, which reflects parasympathetic nerve activity, showed no significant difference. With regard to the psychological indices, viewing real flowers resulted in “comfortable”, “relaxed”, and “natural” feelings. The findings indicate that visual stimulation with real pansies induced physiological and psychological relaxation effects in high school students.
... Wood oil from the above tree was found to increase natural killer cell activity and improve immune functions [37]. In addition, it has been reported that inhalation of α-pinene and D-limonene, which are major components of forest odor, decreased systolic blood pressure [38], enhanced parasympathetic nervous activity, and decreased heart rate [39,40]. ...
Article
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This study was aimed to clarify the physiological effects of visual stimulation using forest imagery on activity of the brain and autonomic nervous system. Seventeen female university students (mean age, 21.1 ± 1.0 years) participated in the study. As an indicator of brain activity, oxyhemoglobin (oxy-Hb) concentrations were measured in the left and 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 ratio of low-frequency (LF) and high-frequency components (LF/HF), which reflected sympathetic nervous activity, were measured. Forest and city (control) images were used as visual stimuli using a large plasma display window. After sitting at rest viewing a gray background for 60 s, participants viewed two images for 90 s. During rest and visual stimulation, HRV and oxy-Hb concentration in the prefrontal cortex were continuously measured. Immediately thereafter, subjective evaluation of feelings was performed using a modified semantic differential (SD) method. The results showed that visual stimulation with forest imagery induced (1) a significant decrease in oxy-Hb concentrations in the right prefrontal cortex and (2) a significant increase in perceptions of feeling "comfortable," "relaxed," and "natural."
... Igarashi et al. [26,27] and Ikei et al. [28] reported that olfactory stimulation from flower oils, such as rose, orange, perilla essential oil, or Hinoki cypress leaf, led to physiological and psychological relaxation by decreasing oxyhemoglobin (oxy-Hb) concentration in the right prefrontal cortex and increased parasympathetic nervous activity. Moreover, olfactory stimulation with Japanese cedar chips led to a physiological relaxation effect by decreasing total hemoglobin concentration in the left and right prefrontal cortex and systolic blood pressure [29]. Kimura et al. [30] reported exposure to rooms with hiba wood as visual and olfactory stimulation decreased systolic and diastolic blood pressure and salivary amylase activity compared to a room with no hiba wood. ...
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The objective of this study was to compare physiological and psychological relaxation by assessing heart rate variability (HRV), prefrontal cortex activity, and subjective indexes while subjects performed a task with and without foliage plants. In a crossover experimental design, 24 university students performed a task transferring pots with and without a foliage plant for 3 min. HRV and oxyhemoglobin (oxy-Hb) concentration in the prefrontal cortex were continuously measured. Immediately thereafter, subjective evaluation of emotions was performed using a modified semantic differential (SD) method and a profile of mood state questionnaire (POMS). Results showed that the natural logarithmic (ln) ratio of low frequency/high frequency, as an estimate of sympathetic nerve activity, was significantly lower while performing the task with foliage plants for the average 3 min measurement interval. Oxy-Hb concentration in the left prefrontal cortex showed a tendency to decrease in the 2–3 min interval in the task with foliage plants compared to the task without plants. Moreover, significant psychological relaxation according to POMS score and SD was demonstrated when the task involved foliage plants. In conclusion, the task involving foliage plants led to more physiological and psychological relaxation compared with the task without foliage plants.
... In the analysis of air quality, α-pinene was the most abundant VOC in rural area. A previous indoor study by Tsunetsugu et al. [56] reported that Japanese cedar scent, dominated by α-pinene compounds, can decrease systolic blood pressure and total hemoglobin concentration in the prefrontal cortex. On the basis of this previous finding, we speculated that the VOCs in the air in rural area might have affected the positive health outcomes in this study. ...
Article
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Despite an increasing attention and public preference for rural amenities, little evidence is available on the health benefits of a rural environment. In this study, we identified physiological and psychological benefits of exposure to a rural environment using multiparametric methods. Twelve young male adults participated in a 3-day field experiment (mean ± standard deviation age, 22.3 ± 1.3 years). Sleeping environment, diet program, physical activities, and other factors possibly affecting physiological responses were controlled during experiment period. For all participants, salivary cortisol concentration, heart rate variability, and blood pressure were measured at rural and urban field sites. Self-evaluation questionnaires were administered to analyze the psychological states in two different environments. Volatile compounds in the air were also analyzed to investigate air quality. The data were compared between rural and urban environments. The data showed that exposure to a rural environment reduced stress hormone secretion and sympathetic nervous activity and increased parasympathetic nervous activity. Short-term exposure to a rural environment also improved mood states. Our findings indicate that exposure to a rural environment effectively reduced physiological stress and enhanced psychological well-being.
Article
This study aimed to demonstrate the effects of forest-derived visual, auditory, and combined stimulation on brain activity, autonomic nervous system activity, and subjective spatial impressions. The participants included 20 Japanese female university students (age 22.1 ± 1.8 years). Each participant viewed a gray image for 60 s with no sound (rest period), followed by an image of a forest scene with no sound (visual stimulation), a gray image with forest sounds (auditory stimulation), an image of a forest scene with forest sounds (combined stimulation), and a gray image with no sound (control) for 90 s. As indicators, near-infrared spectroscopy, heart rate variability measurement, heart rate monitoring, and modified semantic differential method were used. Compared to the control condition, combined stimulation significantly decreased oxyhemoglobin (oxy-Hb) concentrations in both prefrontal cortices and increased parasympathetic nervous activity, reflecting a relaxed state; visual and auditory stimulation significantly decreased the oxy-Hb concentration in the right prefrontal cortex; and “comfortable,” “relaxed,” “natural,” and “realistic” feelings increased significantly for all stimulations. In conclusion, forest-derived visual, auditory, and combined stimuli induced physiologically and psychologically relaxing effects, and physiological relaxation was more pronounced under combined stimulus.
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A newly devised procedure of time series analysis, which is a linearized version of the nonlinear least squares method combined with the maximum entropy spectral analysis method, was proposed and applied to the annual sunspot number data from 1700 to 1991. Multiple periodicities of the temporal variation were elucidated in detail. The solar cycle of a 11.04-year period accompanied with the solar cycle multiplets, the periods of 50.41 years, the so-called ``Yoshimura cycle'', and 107.11 years corresponding to the cycle of century-scale minima, for example, were clearly observed. The optimum least squares fitting curve for the data was extended over the past two millennia and the next millennium. The past grand minima such as the Maunder minimum were confirmed in the past extrapolation curve, and the next centennial minimum was predicted to occur between 2000 and 2030.
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The effect on the pentobarbital sleep time by olfactory stimulation with various odorants was investigated using mice to appraise the physiological or psychological significance of olfactory information. The sleep time was determined as the time elapsed between intraperitoneal pentobarbital administration and the first time that the animal was able to spontaneously right itself. The sleep time was affected by inhalation of some odorants compared to pure air controls, but not by others. The sleep time was prolonged by terpinyl acetate and phenethyl alcohol, and was shortened by lemon oil and jasmin oil. However, neither potentiation nor attenuation of pentobarbital action by odorant inhalation was observed when using anosmic mice produced by intranasal zinc sulphate treatment. In conclusion, olfactory stimulation associated with odorant inhalation influences the pentobarbital sleep time, suggesting that olfactory information may have a more potent influence on the physiological and psychological status than has previously been thought.
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A number of medical applications of near-infrared spectroscopy are growing closer to clinical acceptance, and new techniques involving both spectroscopy and imaging are evolving rapidly. In vivo spectroscopy and, more recently, imaging techniques are largely based upon optical electronic transitions involving the metal centers of hemoglobin (blood), myoglobin (muscle) and cytochrome aa3 (mitochondria). The wide variety of near-IR based applications includes heart and stroke research, monitoring cerebral oxygenation of premature babies, and 'functional activation' (response of brain to mental tasks). All of these applications are founded upon changes in hemoglobin O2 saturation; these changes are monitored by following trends in the near-infrared absorptions of deoxyhemoglobin (760 nm) and oxyhemoglobin (920 nm). The same absorptions provide a basis for imaging regional variations in blood oxygenation. This report presents and discusses examples, both from the literature and from our recent work, of near-infrared spectroscopy and imaging in medical applications.
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In order to realize a hand-held monitor of the sympathetic nervous system, we fabricated a completely automated analytical system for salivary amylase activity using a dry-chemistry system. This was made possible by the fabrication of a disposable test-strip equipped with built-in collecting and reagent papers and an automatic saliva transfer device. In order to cancel out the effects of variations in environmental temperature and pH of saliva, temperature- and pH-adjusted equations were experimentally determined, and each theoretical value was input into the memory of the hand-held monitor. Within a range of salivary amylase activity between 10 and 140 kU/l, the calibration curve for the hand-held monitor showed a coefficient with R(2)=0.97. Accordingly, it was demonstrated that the hand-held monitor enabled a user to automatically measure the salivary amylase activity with high accuracy with only 30 microl sample of saliva within a minute from collection to completion of the measurement. In order to make individual variations of salivary amylase activity negligible during driver fatigue assessment, a normalized equation was proposed. The normalized salivary amylase activity correlated with the mental and physical fatigue states. Thus, this study demonstrated that an excellent hand-held monitor with an algorithm for normalization of individuals' differences in salivary amylase activity, which could be easily and quickly used for evaluating the activity of the sympathetic nervous system at any time. Furthermore, it is suggested that the salivary amylase activity might be used as a better index for psychological research.
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Previously, we observed that olfactory stimulation with scent of lavender oil (SLVO) suppressed sympathetic nerve activities and elevated gastric vagal (parasympathetic) nerve activity (GVNA), decreased plasma glycerol concentration and body temperature, and enhanced appetite in rats. Here, we further showed that olfactory stimulation with SLVO lowered renal sympathetic nerve activity (RSNA) and blood pressure (BP) and elevated GVNA in urethane-anesthetized rats. Olfactory stimulation with linalool, a component of lavender oil, also elicited decreases in RSNA and BP and an increase in GVNA in urethane-anesthetized rats. Anosmia induced by pretreatment of the nasal cavity by application of ZnSO4 eliminated the effects of both SLVO and scent of linalool on RSNA, GVNA and BP. Furthermore, intracerebroventricular administration of thioperamide, a histaminergic H3-antagonist, abolished the suppression of RSNA and BP as well as the elevation of GVNA mediated by both SLVO and scent of linalool. Finally, bilateral lesions of the hypothalamic suprachiasmatic nucleus (SCN) eliminated RSNA and BP suppression and the elevation of GVNA due to SLVO or linalool. Thus, it was concluded that scent of lavender oil and its active component, linalool, affects autonomic neurotransmission and reduces blood pressure through the central histaminergic nervous system and the SCN.
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We examined the effects of odorant inhalation on the sleep-wake states in rats. Odorants used in the experiment were clove, jasmine, lavender, lemon, peppermint, pine, rose, sandalwood, valerian, and ylang-ylang. Valerian and rose inhalation significantly prolonged the pentobarbital-induced sleeping time, whereas lemon inhalation significantly shortened it. The effect of valerian inhalation was markedly noticeable. In the anosmic rats, a significant effect of odorants on the pentobarbital sleep time was not seen. Electroencephalographic studies on natural sleep revealed that rose inhalation did not exert any significant effect on sleep, but a significant shortening in sleep latency and a significant prolonging in total sleep time were observed with valerian inhalation, whereas a significant prolonging in sleep latency was observed with lemon inhalation. Such effects of valerian and lemon inhalation were not admitted in anosmic rats. gamma-Aminobutyric acid (GABA) transaminase assay indicates that valerian inhalation decreases the activity of the enzyme and enhances GABA activity. Although valerian has been reported to exert a good effect for sleep as a medicine for internal use, the present study is the first medical report suggesting that the inhalation of valerian may enhance the sleep. On the other hand, the present results may suggest the possibility that lemon inhalation may cause a worsening of insomnia symptoms.
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It is well known that odors affect behaviors and autonomic functions. Previous studies reported that some compounds in cedar wood essence induced behavioral changes including sedative effects. In the present study, we analyzed cardiovascular and respiratory functions while subjects were inhaling fumes of pure compound (Cedrol) which was extracted from cedar wood oil. Vaporized Cedrol (14.2+/-1.7 microg/l, 5 l/min) and blank air (5 l/min) were presented to healthy human subjects (n=26) via a face mask, while ECGs, heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), and respiratory rates (RR) were monitored. Statistical analyses indicated that exposure to Cedrol significantly decreased HR, SBP, and DBP compared to blank air while it increased baroreceptor sensitivity. Furthermore, respiratory rate was reduced during exposure to Cedrol. These results, along with the previous studies reporting close relationship between respiratory and cardiovascular functions, suggest that these changes in respiratory functions were consistent with above cardiovascular alterations. Spectral analysis of HR variability indicated an increase in high frequency (HF) component (index of parasympathetic activity), and a decrease in ratio of low frequency to high frequency components (LF/HF) (index of sympathovagal balance) during Cedrol inhalation. Furthermore, Cedrol inhalation significantly decreased LF components of both SBP and DBP variability, which reflected vasomotor sympathetic activity. Taken together, these patterns of changes in the autonomic parameters indicated that Cedrol inhalation induced an increase in parasympathetic activity and a reduction in sympathetic activity, consistent with the idea of a relaxant effect of Cedrol.
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Differences in the cardiovascular responses of individuals with behavior patterns of Type A and Type B were investigated during rest, stress, and recovery by visual stimulation. Thirty healthy undergraduate and graduate students (mean age: 22.18+/-1.44 years) were categorized as Type A (N=14), or Type B (N=16) based on the Kwansei Gakuin's daily life questionnaire. The cardiovascular reactivity of all participants was repetitively monitored for 6 sessions, with each session comprising 3 conditional phases, viz., resting, stress, and post-stress recovery. A gray screen was displayed during resting, displeasure-evoking images were displayed under the stress condition, and video clips of a forest or a control image (a gray screen) were displayed during the recovery condition. When participants were subjected to different stimuli on a 42-inch plasma television screen in each session, electrocardiograms (ECG), impedance cardiograms and the blood pressure (BP) of the respective participants were continuously monitored. According to the results, Type A indicated higher sympathetic reactivity than Type B during resting and under stress. As such, Type A indicated a shorter pre-ejection period (PEP) level during resting and a greater cardiac output (CO) increase under stress than Type B. Furthermore, parasympathetic predominance and parasympathetic antagonism accompanying the enhanced sympathetic activity induced by the unpleasant stress images decreased heart rate (HR) in both Type A and Type B, although the decrease in Type A was relatively meager. Unlike previous studies, the present study demonstrated that Type A indicated more enhanced sympathetic reactivity than Type B in resting physiological arousal levels and visual stimulus-induced stress.
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What is already known about this subject: Relationships between smell sensation and autonomic changes have been studied extensively. However, the possibility that odorants may also act on the lung and lower airway remains unknown. What this study adds: The present results provide the first evidence that the lung and lower airway exert an inhibitory influence on the cardiovascular system in response to Cedrol (odorant) in the air under physiological conditions. Aims: Previous studies reported that Cedrol (odorant) inhalation (CI) induced changes in autonomic balance and baroreceptor sensitivity (BRS) in both healthy subjects and anosmic patients. This suggests that Cedrol may act on the lower airway, and that the pulmonary system may exert an inhibitory influence on the cardiovascular system. Method: To test the above possibility, vaporized Cedrol (64.0 +/- 7.7 10(-9)m) or blank air was directly inhaled through the lower airway from a hole in the trachea, but not through the upper airway, using totally laryngectomized subjects. During the experiment, ECG, systolic (SBP) and diastolic (DBP) blood pressures were measured. Sympathetic and parasympathetic nervous activity was estimated by spectral analyses of variability in these parameters (heart rate variability (HRV), SBP variability (SBPV) and DBP variability (DBPV)). BRS was computed from transfer gain between SBP and the R-R interval of the ECG. Results: SBP and DBP significantly decreased during CI, although there were no significant differences in HR and respiratory rate. BRS significantly increased during CI. The low frequency components of SBPV and DBPV (indices for sympathetic activity) significantly decreased during CI, while high frequency components of HRV (an index for parasympathetic activity) significantly increased. Conclusions: The present experiment using totally laryngectomized patients replicated the similar results in healthy subjects who inhaled Cedrol through the nose, suppression of sympathetic outflow and increase in parasympathetic outflow. These results demonstrated that Cedrol acts on the lower airway and pulmonary system, and suggest a new target for drug therapy of hypertension.