Department of Biology and Otolaryngology, University of Washington, Seattle, Washington, USA.
Department of Undergraduate Neurobiology Program, University of Washington, Seattle, Washington, USA.
J Comp Neurol. 2021 Apr 15;529(6):1255-1265. doi: 10.1002/cne.25019. Epub 2020 Sep 16.
Songbirds learn vocalizations by hearing and practicing songs. As song develops, the tempo becomes faster and more precise. In the songbird brain, discrete nuclei form interconnected myelinated circuits that control song acquisition and production. The myelin sheath increases the speed of action potential propagation by insulating the axons of neurons and by reducing membrane capacitance. As the brain develops, myelin increases in density, but the time course of myelin development across discrete song nuclei has not been systematically studied in a quantitative fashion. We tested the hypothesis that myelination develops differentially across time and song nuclei. We examined myelin development in the brains of the zebra finch (Taeniopygia guttata) from chick at posthatch day (d) 8 to adult (up to 147 d) in five major song nuclei: HVC (proper name), robust nucleus of the arcopallium (RA), Area X, lateral magnocellular nucleus of the anterior nidopallium, and medial portion of the dorsolateral thalamic nucleus (DLM). All of these nuclei showed an increase in the density of myelination during development but at different rates and to different final degrees. Exponential curve fits revealed that DLM showed earlier myelination than other nuclei, and HVC showed the slowest myelination of song nuclei. Together, these data show differential maturation of myelination in different portions of the song system. Such differential maturation would be well placed to play a role in regulating the development of learned song.
鸣禽通过听觉和练习歌曲来学习发声。随着歌曲的发展，节奏变得更快、更精确。在鸣禽的大脑中，离散的核形成相互连接的髓鞘化回路，控制着歌曲的习得和产生。髓鞘通过隔离神经元的轴突和减少膜电容来增加动作电位传播的速度。随着大脑的发育，髓鞘的密度增加，但在定量的方式中，离散鸣禽核中的髓鞘发育的时间过程尚未得到系统研究。我们检验了髓鞘在不同时间和鸣禽核中发育不同的假设。我们在五种主要的鸣禽核（HVC、RA、Area X、前脑外侧大细胞核和背外侧丘脑核的内侧部分）中检查了斑胸草雀（Taeniopygia guttata）在孵化后第 8 天到成年（最多 147 天）的大脑中的髓鞘发育情况。所有这些核都显示出髓鞘密度在发育过程中增加，但增加的速度和最终的程度不同。指数曲线拟合表明，DLM 的髓鞘化比其他核更早，而 HVC 的髓鞘化是鸣禽核中最慢的。这些数据共同表明，髓鞘化在不同的歌唱系统部分存在不同的成熟度。这种差异成熟将很好地发挥作用，调节学习歌曲的发展。
