Vates G E, Vicario D S, Nottebohm F
Laboratory of Animal Behavior, Rockefeller University, New York, New York 10021, USA.
J Comp Neurol. 1997 Apr 7;380(2):275-90.
Songbirds have a complex vocal repertoire, much of which is learned by imitation. The vocal motor system of songbirds includes a set of telencephalic pathways dedicated to the acquisition and production of learned song. The main vocal motor pathway goes from the high vocal center (HVC) to the robust nucleus of the archistriatum (RA), which in turn innervates mesencephalic and medullary nuclei involved in vocalization. We used neural tract tracers (biotinylated dextran amines, fluorescein- and rhodamine-linked dextran amines, and Fluorogold) to show that RA of adult male canaries (Serinus canaria) and zebra finches (taeniopygia guttata) sends an ipsilateral projection to the posterior portion of the dorsomedial thalamic nucleus (DMP). DMP projects to the medial portion of the magnocellular nucleus of the anterior neostriatum (mMAN), which is known to project to HVC, forming a feedback circuit. We also observed that the projection from DMP to mMAN is bilateral. Extracellular multi-unit recordings from awake restrained subjects have demonstrated that mMAN has auditory responses that are selective for the bird's own song. These auditory responses are similar to responses recorded simultaneously in HVC, but with a longer latency, suggesting that mMAN receives auditory information from HVC through the circuit we have described. We also saw a weaker projection from RA to the medial part of the dorsolateral nucleus of the thalamus (DLM), which is known to project to the lateral portion of the magnocellular nucleus of the anterior neostriatum (IMAN). IMAN is known to project to RA, completing yet another feedback circuit; IMAN is also part of the anterior forebrain pathway, which plays an essential role in song learning. These thalamo-telencephalic circuits are similar to the thalamo-cortical circuits found in mammalian motor systems, and we suggest that the signals carried by these loops may be important for song perception, song learning, song production, and/or the bilateral coordination of vocal motor commands.
鸣禽拥有复杂的发声曲目，其中大部分是通过模仿习得的。鸣禽的发声运动系统包括一组专门用于习得歌曲的获取和产生的端脑通路。主要的发声运动通路从高位发声中枢（HVC）通向古纹状体粗核（RA），而RA又支配参与发声的中脑和延髓核团。我们使用神经束示踪剂（生物素化葡聚糖胺、荧光素和罗丹明连接的葡聚糖胺以及荧光金）来表明成年雄性金丝雀（Serinus canaria）和斑胸草雀（Taeniopygia guttata）的RA向背内侧丘脑核（DMP）的后部发出同侧投射。DMP投射到前新纹状体大细胞内侧核（mMAN）的内侧部分，已知mMAN投射到HVC，形成一个反馈回路。我们还观察到从DMP到mMAN的投射是双侧的。对清醒受限受试者进行的细胞外多单位记录表明，mMAN具有对鸟类自身歌声有选择性的听觉反应。这些听觉反应与在HVC中同时记录到的反应相似，但潜伏期更长，这表明mMAN通过我们所描述的回路从HVC接收听觉信息。我们还观察到从RA到丘脑背外侧核（DLM）内侧部分的投射较弱，已知DLM投射到前新纹状体大细胞外侧核（IMAN）的外侧部分。已知IMAN投射到RA，从而完成另一个反馈回路；IMAN也是前脑通路的一部分，在前脑通路在歌曲学习中起着至关重要的作用。这些丘脑 - 端脑回路与哺乳动物运动系统中发现的丘脑 - 皮质回路相似，我们认为这些回路所携带的信号可能对歌曲感知、歌曲学习、歌曲产生和/或发声运动指令的双侧协调很重要。
