Wild J Martin
Faculty of Medical and Health Sciences, University of Auckland, PB 92019, Auckland, New Zealand.
Ann N Y Acad Sci. 2004 Jun;1016:438-62. doi: 10.1196/annals.1298.016.
Reviews of the songbird vocal control system frequently begin by describing the forebrain nuclei and pathways that form anterior and posterior circuits involved in song learning and song production, respectively. They then describe extratelencephalic projections upon the brainstem respiratory-vocal system in a manner suggesting, quite erroneously, that this system is itself well understood. One aim of this chapter is to demonstrate how limited is our understanding of that system. I begin with an overview of the neural network for the motor control of song production, with a particular emphasis on brainstem structures, including the tracheosyringeal motor nucleus (XIIts), which innervates the syrinx, and nucleus retroambigualis (RAm), which projects upon XIIts and upon spinal motor neurons innervating expiratory muscles. I describe the sources of afferent projections to XIIts and RAm and discuss their probable role in coordinating the bilateral activity of respiratory and syringeal muscles during singing. I then consider the routes by which sensory feedback, which could arise from numerous structures involved in singing, might access the song system to guide song learning, maintain accurate song production, and inform the song system of the requirements for air. I describe possible routes of access of auditory feedback, which is known to be necessary for song learning and maintenance, and identify potential sites of interaction with somatosensory and visceral feedback that could arise from the syrinx, the lungs and air sacs, and the upper vocal tract, including the jaw. I conclude that the incorporation of brainstem-based respiratory-vocal variables is likely to be a necessary next step in the construction of more sophisticated models of the control of vocalization.
对鸣禽发声控制系统的综述往往开篇就描述前脑核团和神经通路，这些核团和通路分别构成了参与鸣叫学习和鸣叫产生的前、后通路。接着，它们以一种相当错误的方式描述了脑外投射至脑干呼吸 - 发声系统的情况，暗示这个系统本身已被充分理解。本章的一个目的就是展示我们对该系统的理解是多么有限。我首先概述用于控制鸣叫产生的运动神经网络，特别强调脑干结构，包括支配鸣管的气管鸣肌运动核（XIIts），以及投射至 XIIts 和支配呼气肌的脊髓运动神经元的疑后核（RAm）。我描述了 XIIts 和 RAm 的传入投射来源，并讨论它们在唱歌过程中协调呼吸肌和鸣管肌双侧活动可能发挥的作用。然后，我考虑来自参与唱歌的众多结构的感觉反馈可能通过哪些途径接入鸣叫系统，以指导鸣叫学习、维持准确的鸣叫产生，并向鸣叫系统传达对空气的需求。我描述了已知对鸣叫学习和维持必不可少的听觉反馈的可能接入途径，并确定了与可能来自鸣管、肺和气囊以及包括下颌在内的上呼吸道的体感和内脏反馈相互作用的潜在部位。我得出结论，纳入基于脑干的呼吸 - 发声变量可能是构建更复杂的发声控制模型的必要下一步。
