Cortical, descending and reflex control of human inspiratory muscles

在所有的骨骼肌中，呼吸肌执行最关键的动作，即它们保持通气。呼吸肌的神经控制必须被精细地整合，以在我们清醒、睡眠、锻炼、进食和说话时保持通气。呼吸肌的神经回路是独一无二的。呼吸肌的控制与肢体肌肉的控制不同，因为呼吸运动神经元被有节奏地激活，但通过两条下行通路控制。在自动呼吸过程中，下行神经驱动来自脑干中的中央呼吸模式发生器。通过这个系统，干扰被反射性地补偿，而不需要有意识的努力。然而，除了自动控制之外，呼吸也可以从运动皮层主动控制，例如在讲话或屏气期间。然而，在人类中，这两个中心之间的神经连接和相互作用却知之甚少。除了下行信号外，吸气肌的活动还受到感觉反射输入的影响。拟议的研究将调查人类吸气肌肉控制的三个方面，这些肌肉的作用是将空气“泵”入肺部，而上气道“扩张”肌肉的作用是保持气道开放。因为在安静的呼吸中呼气通常是被动的，我们将重点放在吸气的神经控制上。首先，我们将研究阻塞性睡眠呼吸暂停患者和非阻塞性睡眠呼吸暂停患者的“泵肌”和“扩张肌”的反射联系。第二，我们将使用单个运动单位记录来研究吸气肌的下行控制。此外，我们将首次对舌头的单个运动单位活动进行详细分析。这种肌肉在我们睡觉时非常有助于保持呼吸。最后，我们将研究运动皮质和髓质之间的相互作用，在控制呼吸，相对较少的是在清醒的人知道。

Of all the skeletal muscles, the breathing muscles perform the most crucial action, that is, they maintain ventilation. The neural control of respiratory muscles must be finely integrated to maintain ventilation while we are awake, asleep, exercising, eating and talking. The neural circuitry for the respiratory muscles is unique. Control of respiratory muscles differs from that of limb muscles because the respiratory motoneurones are activated rhythmically but are controlled via two descending pathways. During automatic breathing, descending neural drive arises from the central respiratory pattern generator in the brainstem. Through this system, disturbances are reflexly compensated for without conscious effort. However, in addition, to automatic control, respiration can also be controlled voluntarily from the motor cortex, for example during speech or a breath hold. However, in humans the neural connections and interactions between these two centres are poorly understood. In addition to descending signals, the activity of inspiratory muscles is affected by sensory reflex inputs. The proposed studies will investigate three aspects of the control of human inspiratory muscles that act to 'pump' air into the lungs and upper airway 'dilator' muscles that act to keep the airway open. Because expiration is usually passive during quiet breathing we will focus on the neural control of inspiration. First, we will investigate some of the reflex connections of human 'pump' and 'dilator' muscles in people with and without obstructive sleep apnoea. Second, we will study the descending control of inspiratory muscles using single motor unit recordings. In addition, we will make the first detailed analysis of single motor unit activity from the tongue. This muscle critically helps preserve breathing when we sleep. Finally, we will examine the interactions between the motor cortex and medulla in the control of breathing about which relatively little is known in awake humans.