Bailey E Fiona, Rice Amber D, Fuglevand Andrew J
Department of Physiology, College of Medicine, University of Arizona, Tucson, AZ 85721-0093, USA.
J Neurophysiol. 2007 Jan;97(1):933-6. doi: 10.1152/jn.00737.2006. Epub 2006 Oct 4.
The tongue participates in a range of complex oromotor behaviors, including mastication, swallowing, respiration, and speech. Previous electromyographic studies of the human tongue have focused on respiratory-related tongue muscle activities and their role in maintaining upper airway patency. Remarkably, the activities of human hypoglossal motor units have not been studied during the execution of voluntary maneuvers. We recorded single motor unit activity using tungsten microelectrodes in the genioglossus muscle of 10 healthy human subjects performing both slow tongue protrusions and a static holding maneuver. Displacement of the tongue was detected by an isotonic transducer coupled to the lingual surface through a customized lever arm. For protrusion trials, the firing rate at recruitment was 13.1 +/- 3 Hz and increased steeply to an average of 24 +/- 6 Hz, often with very modest increases in tongue protrusion. For the static holding task, the average firing rate was 16.1 +/- 4 Hz, which is surprisingly high relative to limb motor units. The average coefficient of variation of interspike intervals was approximately 20% (range, 10-28%). These are the first recordings of their type obtained in human subjects and provide an initial glimpse into the voluntary control of hypoglossal motoneurons during tongue movements presumably instigated by activity in the motor cortex.
舌头参与一系列复杂的口面部运动行为，包括咀嚼、吞咽、呼吸和言语。以往对人类舌头的肌电图研究主要集中在与呼吸相关的舌肌活动及其在维持上呼吸道通畅中的作用。值得注意的是，在执行自主动作期间，尚未对人类舌下运动单位的活动进行研究。我们使用钨微电极记录了10名健康人类受试者在进行缓慢伸舌和静态保持动作时颏舌肌的单个运动单位活动。通过一个定制的杠杆臂与舌面相连的等张换能器检测舌头的位移。在伸舌试验中，募集时的放电频率为13.1±3Hz，并急剧增加至平均24±6Hz，而舌头伸出的增加通常非常小。对于静态保持任务，平均放电频率为16.1±4Hz，相对于肢体运动单位而言，这一频率出奇地高。峰间间隔的平均变异系数约为20%（范围为10 - 28%）。这些是在人类受试者中首次获得的此类记录，并初步揭示了在可能由运动皮层活动引发的舌头运动过程中舌下运动神经元的自主控制情况。
