Vates G E, Nottebohm F
Laboratory of Animal Behavior, Rockefeller University, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 1995 May 23;92(11):5139-43. doi: 10.1073/pnas.92.11.5139.
The song system of birds consists of several neural pathways. One of these, the anterior forebrain pathway, is necessary for the acquisition but not for the production of learned song in zebra finches. It has been shown that the anterior forebrain pathway sequentially connects the following nuclei: the high vocal center, area X of lobus parolfactorius, the medial portion of the dorsolateral thalamic nucleus, the lateral magnocellular nucleus of anterior neostriatum (IMAN), and the robust nucleus of the archistriatum (RA). We now show in zebra finches (Taeniopygia guttata) that IMAN cells that project to RA also project to area X, forming a feedback loop within the anterior forebrain pathway. The axonal endings of the IMAN projection into area X form cohesive and distinct domains. Small injections of tracer in subregions of area X backfill a spatially restricted subset of cells in IMAN, that, in turn, send projections to RA that are arranged in horizontal layers, which may correspond to the functional representation of vocal tract muscles demonstrated by others. We infer from our data that there is a myotopic representation throughout the anterior forebrain pathway. In addition, we suggest that the parcellation of area X into smaller domains by the projection from IMAN highlights a functional architecture within X, which might correspond to units of motor control, to the representation of acoustic features of song, or both.
鸟类的鸣唱系统由几条神经通路组成。其中一条，即前脑通路，对于斑胸草雀习得鸣叫是必需的，但对于其发出习得鸣叫则不是必需的。研究表明，前脑通路依次连接以下核团：高级发声中枢、嗅觉叶X区、背外侧丘脑核的内侧部分、新纹状体前部的外侧大细胞核（IMAN）和古纹状体粗核（RA）。我们现在在斑胸草雀（Taeniopygia guttata）中发现，投射到RA的IMAN细胞也投射到X区，在前脑通路内形成一个反馈回路。IMAN投射到X区的轴突末梢形成了连贯且不同的区域。在X区的子区域中进行微量示踪剂注射，会使IMAN中空间受限的一部分细胞逆向标记，这些细胞继而向RA发出投射，这些投射呈水平层状排列，这可能与其他人所展示的声道肌肉的功能表征相对应。我们从数据中推断，在前脑通路中存在肌位表征。此外，我们认为，IMAN的投射将X区分成更小的区域，这突出了X区内的一种功能架构，它可能对应于运动控制单元、鸣叫声学特征的表征，或者两者皆是。
