Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
J Comp Neurol. 2010 Aug 1;518(15):3086-100. doi: 10.1002/cne.22383.
Songbirds use a complex network of discrete brain areas and connecting fiber tracts to sing their song, but our knowledge of this circuitry may be incomplete. The forebrain area, "caudal mesopallium" (CM), has received much attention recently for its song-related activities. HVC, a prominent song system nucleus, projects to a restricted area of the CM known as the avalanche nucleus (Av). However, the other connections of Av remain unknown. Here we used tract-tracing methods to examine the connections of Av to other song system nuclei. Injections of biotinylated dextran amine (BDA) into Av labeled both afferent terminals and neurons in HVC and the interfacial nucleus of the nidopallium (NIf), suggesting that there is complex feedforward and feedback communication between these nuclei (HVC<-->Av<-->NIf). Labeled neurons were also found in the uvaeform nucleus (Uva), which was substantiated by BDA injections into Uva that labeled terminals in Av. Double fluorescent tracing experiments confirm that both HVC and Uva project to Av. The present study adds complex new connections that expand the traditional song system circuitry into the caudal mesopallium. These new pathways are likely to have broad implications for deciphering how this intricate system works.
鸣禽通过一个复杂的离散脑区网络和连接纤维束来鸣唱，但我们对这个回路的了解可能并不完整。脑前区“中脑后部”（CM）因其与鸣叫相关的活动而受到广泛关注。突出的鸣叫系统核团“下顶核”（HVC）投射到 CM 的一个称为雪崩核（Av）的受限区域。然而，Av 的其他连接仍不清楚。在这里，我们使用示踪方法研究了 Av 与其他鸣叫系统核团的连接。将生物素化葡聚糖胺（BDA）注入 Av 标记了 HVC 和中脑顶间核的界面核（NIf）中的传入末端和神经元，表明这些核团之间存在复杂的前馈和反馈通讯（HVC<-->Av<-->NIf）。在 Uva 中进行 BDA 注射标记了 Av 中的末端，证实了 Uva 中的标记神经元的存在。双荧光示踪实验证实 HVC 和 Uva 都投射到 Av。本研究增加了复杂的新连接，将传统的鸣叫系统回路扩展到中脑后部。这些新的通路可能对破译这个错综复杂的系统如何工作具有广泛的意义。
