Neuromuscular control of the mammalian tongue

舌肌参与各种活动，如呼吸、吞咽、说话和咀嚼， 因此对动态平衡至关重要。来自八种不同肌肉的纤维插入哺乳动物的舌头 并控制其运动、形状和硬度，但对舌肌运动单位的控制 基本上被忽视了。我们的目标是探索中枢神经系统如何控制模式化的行为(驱动力 由呼吸中枢模式生成器(CPG)控制)，涉及多个肌肉作用于 单一的机械结构，通过解决以下问题：1)驱动舌头突出的运动神经元 牵引肌接受显著的共同突触输入，即使它们有相反的 舌头上的机械作用，提示激动剂-拮抗剂共激活控制舌头 僵硬；2)与呼吸有关的舌头和“主要”吸气肌(横隔膜、肋间)的输入是 来自独立来源；3)模型预测，随着运动单位尖峰序列变得更加多变 对细胞的突触输入增加。这可以通过测量尖峰序列变异性的变化来测试 当兴奋性突触输入叠加在从呼吸发出的潜在输入上时 支配与呼吸相关活动的舌肌的运动单位分为两个功能单位 人群；那些开车去肌肉时编码的人增加了，而那些不是的人增加了。我们建议 尽管突触输入增加，但没有编码的运动单位的放电率饱和；而我们 将检验这一假设；5)肌肉中的单个运动单位至少由四个特定于任务的亚单位组成。 总体(吸气、呼气、紧张性和呼气-吸气单位)和给定任务的特殊性 单位取决于它的收缩特性。实验将在麻醉状态下自发进行 会呼吸的成年大鼠。使用的技术包括单运动单位电生理学、互相关 呼吸机排气量的分析和测量。这些实验的结果将有助于 制定阻塞性睡眠呼吸暂停、吞咽障碍等治疗策略所需的知识库 和口腔面部运动障碍。

The tongue muscles participate in such diverse activities as breathing, swallowing, speech and mastication, and are thus critical for homeostasis. Fibers from eight different muscles insert into the mammaliantongue and control its movement, shape and stiffness, but the control of tongue muscle motor units has been largely ignored. Our goal is to explore how the central nervous system controls a patterned behavior (drive controlled by the respiratory central pattern generator, CPG) that involves multiple muscles acting on a single mechanical structure, by addressing the following issues: 1) motoneurons driving tongue protrudor and retractor muscles receive significant common synaptic input even though they have opposite mechanical actions on the tongue, suggesting that agonist-antagonist co-activation controlstongue stiffness; 2) respiratory-related input to tongue and "primary" inspiratory muscles (diaphragm, intercostals) is derived from independent sources; 3) Models predict that motor unit spike trains become more variable as synaptic input to the cell is increased. This can be tested by measuring the change in spike train variability when excitatory synaptic input is superimposed on the underlying input emanating from the respiratory CPG; 4} Motor units innervating tongue muscles with respiratory related activity fall into two functional populations; those that rate code when drive to the muscle increases, and those that do not. Wepropose that the firing rate of motor units that do not rate code saturates despite increases in synaptic input; and we will test this hypothesis; 5) Individual motor units within a muscle comprise at least four, task-specific sub- populations (inspiratory, expiratory, tonic and expiratory-inspiratory units), and the task specificity of a given unit depends on its contractile properties. Experiments will be done in anesthetized, spontaneously breathing adult rats. Techniques used include single motor unit electrophysiology, cross correlation analysis and the measurement of ventilatory output. The results of these experimentswill contribute to the knowledge base needed to develop treatment strategies for obstructive sleep apnea, swallowingdisorders, and oro-facial motor deficits.