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Sensorimotor Control

開催日 2014/9/11
時間 18:00 - 19:00
会場 Room H(304)
Chairperson(s) 花川 隆 / Takashi Hanakawa (国立精神・神経医療研究センター脳病態統合イメージングセンター 先進脳画像研究部 / Department of Advanced Neuroimaging, Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Japan)
高草木 薫 / Kaoru Takakusaki (旭川医科大学医学部 脳機能医工学研究センター / Asahikawa Medical University, The Center for Brain Function and Medical Engineering, Japan)

Exploring the Activity of Fusimotor Neurones in Man

  • O1-H-6-2
  • 角田 尚幸 / Naoyuki Kakuda:1 二橋 元紀 / Genki Futatsubashi:2 渡部 幸司 / Kouji Watanabe:3 福島 敏行 / Toshiyuki Fukushima:3 林 康子 / Yasuko Hayashi:3 長岡 正範 / Masanori Nagaoka:3 
  • 1:社会医療法人財団大和会 東大和病院 / Dept of Neurol, Higashiyamato Hospital, Japan 2:上武大学ビジネス情報学部 / Faculty of Business and Information Sciences, Jobu Univ, Japan 3:順天堂大学大学院リハビリテーション医学 / Dept Rehab, Juntenndo Univ Graduate School of Medicine, Japan 

[Introduction] Discharges of muscle spindle afferents are increased during contractions, suggesting the co-activation of skeletomotor and fusimotor neurones. However, direct recordings of fusimotor neurones have not been reported in man. We propose a method to record the activity of human single fusimotor fibers.
[Methods] Experiments were done in 8 healthy volunteers. Two tungsten microelectrodes were inserted into the radial nerve above elbow, separated by 50mm. Action potentials of a single muscle nerve fiber were recorded by the one electrode, while multi-unit activity by the other. In off-line analyses, multi-unit recordings were averaged, triggered by the action potentials. A small field potential was obtained in the multi-unit recordings. The direction of conduction and its velocity (CV) were determined from the potentials at two sites. If the direction is centrifugal and the CV is slower than 30m/s, the activity would be considered as that of a single fusimotor fiber.
[Results] Action potentials of 29 single fibers were recorded at the distal site. In 6 of them a field potential at the proximal site preceded an action potential at the distal site, indicating the centrifugal conduction. The CV was 65.8-84.8 (median 72.2) m/s. Hence, they were considered as skeletomotor fibers. In other 23 of 29 fibers the conduction was centripetal, so they were afferents. The CV was 38.9-65.8 (51.3) m/s. Action potentials of other 4 single fibers were recorded at the proximal site. All were afferents and the CV was 74.0-91.6 (85.7) m/s. The CV of 23 afferents in which an action potential preceded a field potential was much slower than that of 4 afferents and 6 efferents in which an action potential followed a field potential, suggesting the conduction was significantly delayed when the electrode records action potentials.
[Discussion] Until now we have not recorded the activity of fusimotor fibers yet. Probably it is infrequent to record action potentials of thin fusimotor fibers. Or, instead of fusimotor neurones, skeletofusimotor neurones (so-called beta motoneurones) may be a dominant source of fusimotor action in human forearm muscle spindles.

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