アブストラクト（51巻1号：神奈川歯学）

神奈川歯学

English

Title　： Clenching mitigates fear bradycardia induced by visual stress
Subtitle　： ORIGINAL ARTICLE
Authors　： Yumie ONO*,**, Takero ARII**, Yuhi TSUNODA*, Kimiya ESAKI*, Natsuki NOTSUYU*, Minoru ONOZUKA***, Katsuhiko KIMOTO**
Authors（kana）　：
Organization　： *Health Science and Medical Engineering Laboratory, School of Science and Technology, Meiji University, **Division of Prosthodontics & Oral Rehabilitation, Department of Oral Function and Restoration Graduate School of Dentistry, Kanagawa Dental University, ***Department of Judo Therapy and Medical Science, Faculty of Medical Science, Nippon Sport Science University
Journal　： Kanagawa Shigaku
Volume　： 51
Number　： 1
Page　： 20-26
Year/Month　： 2016 / 6
Article　： Original article
Publisher　： Kanagawa Odontological Society
Abstract　： [Abstract] Fear bradycardia is a freezing-like response caused by stressful visual stimuli. It is a parasympathetically-dominated autonomic defensive response, and is implicated in the development and maintenance of psychopathology in humans. We investigated whether clenching, a possible behavioral approach to relieve emotional stress, affects visually-evoked fear bradycardia. Twenty-five healthy young adult males were presented with neutral or unpleasant images of a body or body parts while wearing a telemetry electrocardiograph to assess their heart rate on two separate experimental days. In a cross-over design of picture viewing session, a 1-mm-thick maxillary mouthpiece was adapted (with clenching), or not adapted (without clenching). The participants evaluated the emotional valence and arousal levels of each picture at the end of each experimental day. Subjective emotional valence and arousal levels, heart rate, and autonomic nervous activity derived from heart-rate variability (HRV) were compared between the conditions by either the paired t-test or the Wilcoxon signed rank test depending on the normality of the data. Clenching significantly increased heart rate and counteracted fear bradycardia during unpleasant picture stimulation although it failed to alter subjective valence and arousal levels of both negative and neutral visual stimuli. Time-frequency analysis of the HRV further demonstrated that clenching suppressed the acute increase of the parasympathetic response (high-frequency (HF) component of HRV) to the unpleasant pictures and prevented fear bradycardia. The suppression of the HF component was neither observed in the case of negative visual stimuli without clenching nor in the case of clenching without visual stimuli, suggesting the possible interaction of clenching-related neuronal activity with fear-induced cardiac autonomic control. Considering the significant role of freezing in the development of psychopathology, our results suggest that clenching is an easy and cost-effective tool to dampen strong visual stress. A possible application would be protecting rescue workers on duty in a disaster situation.
Practice　： Dentistry
Keywords　： Heart rate variability, fear bradycardia, emotional