Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, United States of America.
PLoS One. 2023 Nov 16;18(11):e0285652. doi: 10.1371/journal.pone.0285652. eCollection 2023.
Diverse dopamine (DA) pathways send distinct reinforcement signals to different striatal regions. In adult songbirds, a DA pathway from the ventral tegmental area (VTA) to Area X, the striatal nucleus of the song system, carries singing-related performance error signals important for learning. Meanwhile, a parallel DA pathway to a medial striatal area (MST) arises from a distinct group of neighboring DA neurons that lack connectivity to song circuits and do not encode song error. To test if the structural and functional segregation of these two pathways depends on singing experience, we carried out anatomical studies early in development before the onset of song learning. We find that distinct VTA neurons project to either Area X or MST in juvenile birds before the onset of substantial vocal practice. Quantitative comparisons of early juveniles (30-35 days post hatch), late juveniles (60-65 dph), and adult (>90 dph) brains revealed an outsized expansion of Area X-projecting neurons relative to MST-projecting neurons in VTA over development. These results show that a mesostriatal DA system dedicated to social communication can exist and be spatially segregated before the onset of vocal practice and associated sensorimotor experience.
不同的多巴胺 (DA) 途径向不同的纹状体区域发送不同的强化信号。在成年鸣禽中，来自腹侧被盖区 (VTA) 到 song 系统的纹状体核区 X 的 DA 途径携带与 singing 相关的表现错误信号，这些信号对学习很重要。与此同时，来自邻近 DA 神经元的平行 DA 途径到一个内侧纹状体区 (MST)，这些神经元缺乏与 song 回路的连接，也不编码 song 错误。为了测试这两种途径的结构和功能是否依赖于 singing 经验，我们在 song 学习开始之前的早期发育阶段进行了解剖学研究。我们发现，在大量 vocal 练习开始之前，处于幼年（孵化后 30-35 天）的鸟类中有不同的 VTA 神经元投射到 Area X 或 MST。对早期幼鸟（30-35 天）、晚期幼鸟（60-65 天）和成年（>90 天）大脑的定量比较显示，在发育过程中，VTA 中相对于 MST 投射神经元，Area X 投射神经元的数量显著增加。这些结果表明，一个专门用于社交交流的中脑纹状体 DA 系统可以在 vocal 练习和相关的感觉运动经验开始之前存在并在空间上分离。
