Auditory-vocal-cholinergic pathway in avian song learning

1. 雄性斑胸草雀通过听觉和动作学习来模仿导师的歌声。鸟类大脑中两个主要的歌唱控制核——高级声乐中枢（high vocal center， HVC）和强壮的纹状体核（robust nucleus of archriatum， RA）接受基底前脑腹侧古纹状体（ventrinal palestriatum， VP）的胆碱能神经支配，可能在鸣叫学习中起关键作用。通过注射神经解剖示踪剂，我们发现了一条从卵泡核（Ov）到VP的地形分离路径，该路径又以地形方式投射到HVC和RA。Ov是主要上行听觉通路中的一个主要中继。实验结果表明，下丘脑负责歌曲学习的胆碱能神经元受到来自下丘脑的听觉信息的调节。听觉-运动的相互作用对于理解鸟类鸣叫的学习和维持至关重要。HVC核被认为是鸟类鸣叫系统中最重要的听觉-运动整合站。然而，关于在哪里以及如何将听觉输入传递到HVC，我们知之甚少。架子是沿HVC腹侧边界的多听觉受体区域，被认为是HVC听觉输入的可能来源。本研究采用实时光学记录技术，研究了脑切片中HVC与HVC周围区域（包括脑架）之间的功能连接。出乎意料的是，对架子区域的电刺激并没有诱导信号传播到HVC，但HVC内的刺激将强信号传播到架子。这些结果表明，架子是接收HVC输出信号的区域，而不是HVC听觉输入的主要来源。

1. Male zebra finches learn to imitate a tutor's song through auditory and motor learning. The two main song control nuclei in the bird brain, the higher vocal center (HVC) and the robust nucleus of the archistriatum (RA), receive cholinergic innervation from the ventral paleostriatum (VP) of the basal forebrain which may play a key role in song learning. By injecting neuroanatomical tracers, we found a topographically segregated pathway from nucleus ovoidahs (Ov) to VP that in turn projects in a topographic fashion to HVC and RA.Ov is a major relay in the main ascending auditory pathway. The results suggest that the cholinergic neurons in the VP responsible for song learning are regulated by auditory information from the Ov.2. Auditory-motor interaction is essential for the understanding of avian song learning and maintenance. The HVC nucleus is thought to be the most important station for auditory-motor integration in the avian song system. However, little is known about where and how auditory inputs are conveyed into the HVC.The shelf, a multi-auditory recipient region along the ventral border of the HVC, is thought to be a possible source of auditory inputs to the HVC.Here, we investigated the functional connections between the HVC and surrounding area of the HVC including the shelf in the brain slices, using the real-time optical recording technique. Unexpectedly the electrical stimulation of the shelf region did not induce a signal propagation into the HVC, but stimulation within the HVC propagated strong signals into the shelf. These results suggest that the shelf is the region that receives the output signals from the HVC, rather than a major source of auditory inputs to the HVC.