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Stress, Autonomic Nervous System and Respirarion

開催日 2014/9/12
時間 9:00 - 10:00
会場 Room J(313+314)
Chairperson(s) 堀田 晴美 / Harumi Hotta (地方独立行政法人 東京都健康長寿医療センター研究所 自律神経機能 / Department of Autonomic Neuroscience, Tokyo Metropolitan Institute of Gerontology, Japan)
荒田 晶子 / Akiko Arata (兵庫医科大学 生理学・生体機能部門 / Department of Physiology, Hyogo College of Medicine, Japan)

Effects of Breathing on Motor Evoked Potential of Non-respiratory Forearm Muscles Following Transcranial Magnetic Stimulation

  • O2-J-1-4
  • 蔵田 潔 / Kiyoshi Kurata:1 尾崎 勇 / Isamu Ozaki:2 
  • 1:弘前大学 / Dept.of Physiol, Hirosaki Univ. Graduate Sch.of Med., Japan 2:青森県立保健大学 / Dept Physical Therapy, Faculty of Health Science, Aomori Univ of Health and Welfare, Japan 

Although we are breathing automatically in normal conditions, we can control breathing voluntarily for various purposes. It was shown by imaging studies that the human primary motor cortex (M1) is involved in the voluntary breathing, and that, within the M1, the activated areas are located adjacent to hand and forearm representations. Then, it is likely that excitability of the hand and forelimb areas in the M1 are modulated by breathing. Thus, we examined whether relatively weak voluntary control of respirations as oppose to automatic respirations probed by exhaled carbon dioxide (CO2) levels influence excitability of the primary motor cortex (M1) controlling the non-respiratory hand muscle, using transcranial magnetic stimulation (TMS) over the M1 of eight healthy human subjects. We applied TMS over the left M1 at inspiratory and expiratory phases of both normal breath and voluntary deep breaths in a self-paced manner while respiratory CO2 levels including end-tidal CO2 (ETCO2) were continuously monitored by a capnometer. Motor evoked potentials (MEP) were simultaneously recorded from five hand and forearm muscles: abductor pollicis brevis, first dorsal interosseous muscle, abductor digiti minimi, flexor digitorum superficialis, and extensor indicis of the right hand. We observed that MEP amplitudes of all the recorded muscle increased nearly 50% and their latencies decreased about 1 ms at low ETCO2 levels during deep breaths in comparison with those around 22 ms during normal breaths under higher ETCO2. There was no statistically significant difference in MEP amplitudes and latencies between stimulations at inspiratory and expiratory phases at the same CO2 levels during either normal or deep breaths. These results suggest that relatively weak voluntary drive on respiration system could enhance excitability of the M1 that controls the non-respiratory hand muscle through corticospinal pathway.

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