Neuromuscular control of the mammalian tongue

舌头肌肉参与呼吸、吞咽、说话和咀嚼等多种活动， 因此对体内平衡至关重要。来自八块不同肌肉的纤维插入到舌头中 并控制其运动，形状和刚度，但舌头肌肉运动单位的控制一直是 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一种模式化的行为（驱动力 由呼吸中枢模式发生器（CPG）控制），其涉及作用于呼吸中枢的多个肌肉。 单一的机械结构，通过解决以下问题：1）运动神经元驱动舌运动 和牵开肌接受重要的共同突触输入，即使它们有相反的 机械动作的舌头，这表明，激动剂-拮抗剂共激活控制舌 僵硬; 2）舌和"初级"吸气肌（隔膜、肋间肌）的与发音相关的输入是 来自独立来源; 3）模型预测，运动单位锋电位序列变得更加可变， 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系统发出的潜在输入上时， CPG; 4}具有呼吸相关活动的支配舌肌的运动单位分为两个功能单位 人群;那些当驱动力增加时对代码进行评级的人群，以及那些不这样做的人群。我们建议 尽管突触输入增加，但不对代码进行评级的运动单位的放电率会饱和; 将测试这一假设; 5）肌肉内的单个运动单位包括至少四个，任务特定的子， 群体（吸气、呼气、强直和呼气-吸气单位），以及给定的任务特异性。 单位取决于其收缩性能。实验将在麻醉状态下进行， 呼吸的成年老鼠使用的技术包括单运动单位电生理学，交叉相关 分析和测量制冷量。这些实验的结果将有助于 开发阻塞性睡眠呼吸暂停、吞咽障碍 和口面部运动缺陷。

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.