## Authors
* Yutaka Yano[^1] [^2] [^3]
* Yoshihiro Murata[^3]
* Mutsuo Taniguchi[^3]
* Fumino Okutani[^3]
* Masahiro Yamaguchi[^3]
* Hideto Kaba[^3]
## Abstract
We have observed changes in body reactions during cooking, which is one of the treatment modalities used in occupational therapy. The perception of food-related odors during cooking may have behavioral effects on human activities through the activation of appetitive motivation. Objectives. We investigated whether odor components contained in seasonings could facilitate the human motor system and the specificity of this effect. Methods. The subjects were 72 healthy adults, randomly assigned to a water exposure group, a phenylethyl alcohol (PEA, pleasant rose-like odor) exposure group, and a Japanese soy sauce (Koikuchi Shoyu) exposure group ( each). The subjects’ olfactory sense was stimulated by their sniffing of three different test tubes containing 5 ml of water, PEA, or Japanese soy sauce for 20 sec while they were seated. The modified Functional Reach Test (mFRT), which mimics a functional activity that is required in daily living and assesses a reliable measure of sitting balance, was performed prior to and immediately after the sniffing. Results. Sniffing the soy sauce increased the subjects’ mFRT scores. This facilitation effect was odorant-specific and was absent when the subjects were presented with water or PEA. Conclusions. Cooking interventions are aimed at improving tool-handling skills such as using knives and chopsticks. The results indicate that treatment interventions using odors of seasonings would be effective for improving subjects’ physical functions.
## 1. Introduction
After experiencing a stroke, which is a common cause of long-term disability, many patients with central nervous system (CNS) disorders have difficulty with instrumental activities of daily living (IADLs). Occupational therapists thus work to improve their patients’ performance of IADLs so that they can adapt to daily life and social life, with the goal of enhancing their patients’ quality of life.
Cooking as an occupational therapy activity is an IADL that is aimed at improving mostly tool-handling skills such as using a knife and chopsticks. Cooking has also been found to be important for individuals’ sense of life satisfaction ^[https://doi.org/10.1016%2fj.apmr.2004.10.031] and to be strongly related to a variety of cognitive skills ^[https://doi.org/10.1080%2f09602011003765690]. However, many factors are involved in a patient’s cooking performance, including physical-environmental factors (e.g., the design of a kitchen and tools) and other types of environmental factors such as food-related odor cues.
We have noted changes in the physical reactions of patients with CNS system disorders that occurred during cooking interventions. One of the factors contributing to these changes may be food-related odor cues, which are often strong motivators for eating. Chemosensory perception is the result of an interaction between the olfactory and the trigeminal systems. The olfactory system is responsible for the perception of odor qualities, whereas the trigeminal system conveys sensations such as burning, stinging, pungency, temperature, or pain ^[https://doi.org/10.1016%2fS0167-8760(99)00108-7] ^[https://doi.org/10.1371%2fjournal.pone.0121091]. Neuroimaging studies have shown that stimulation with food-related odors is a potent elicitor of cerebral activity in brain reward circuits, including frontal, ventral striatal, amygdala, and midbrain regions. Compared to nonfood odors, food-related odors generated higher activation in the anterior cingulate cortex, insula, and putamen. We hypothesized that the perception of food-related odors during cooking could modulate the motor system by driving the motivation to eat. Although a number of studies have found beneficial effects of food-related odors on swallowing, postural stability, gait performance, and grasping movement toward a food object, most of the food-related odors so far examined in relation to the motor system were trigeminal stimulants such as black pepper and lavender. Therefore, the relationship between food-related odors and the motor system has not yet been fully clarified.
We thus first selected Japanese soy sauce (Koikuchi Shoyu) as a powerful appetitive cue used for olfactory stimulation, because this is a signature seasoning in Japanese food culture and is easily obtained in daily life. We also suspected that Japanese subjects are less likely to dislike the smell of soy sauce. We then compared changes in the modified Functional Reach Test (mFRT) score, a reliable measure of sitting balance, in healthy individuals divided into stimulation groups (Japanese soy sauce and phenylethyl alcohol (PEA) with a pleasant rose-like odor) and a nonstimulated group (water).
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_The article was trimmed for testing purposes._
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### Conflicts of Interest
The authors declare no conflict of interest.
### License
Copyright © 2019 Yutaka Yano et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
[^1]: HITO Hospital, Shikokuchuo, Ehime 799-0121, Japan
[^2]: Department of Occupational Therapy, Tosa Rehabilitation College, Kochi 781-5103, Japan
[^3]: Department of Physiology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan