The torus semicircularis (TS) of teleosts is a key midbrain center of the lateral line and acoustic sensory systems. To characterize the TS in adult zebrafish, we studied their connections using the carbocyanine tracers applied to the TS and to other related nuclei and tracts. Two main TS nuclei, central and ventrolateral, were differentiable by their afferent connections. From central TS, (TSc) numerous toropetal cells were labeled bilaterally in several primary octaval nuclei (anterior, magnocellular, descending, and posterior octaval nuclei), in the secondary octaval nucleus, in the caudal octavolateralis nucleus, and in the perilemniscular region. In the midbrain, numerous toropetal cells were labeled in the contralateral TSc. In the diencephalon, toropetal cells labeled from the TSc were observed ipsilaterally in the medial prethalamic nucleus and the periventricular posterior tubercle nucleus. TSc toropetal neurons were also labeled bilaterally in the hypothalamic anterior tuberal nucleus (ATN) and ipsilaterally in the parvicellular preoptic nucleus but not in the telencephalon. Tracer application to the medial octavolateralis nucleus revealed contralateral projections to the ventrolateral TS (TSvl), whereas tracer application to the secondary octaval nucleus labeled fibers bilaterally in TSc and neurons in rostral TSc. The TSc sends ascending fibers to the ipsilateral lateral preglomerular region that, in turn, projects to the pallium. Application of DiI to the optic tectum labeled cells and fibers in the TSvl, whereas application of DiI to the ATN labeled cells and fibers in the TSc. These results reveal that the TSvl and TSc are mainly related with the mechanosensory lateral line and acoustic centers, respectively, and that they show different higher order connections.

中文翻译：

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成年斑马鱼半圆环的神经连接

硬骨鱼的半圆环（TS）是侧线和声感觉系统的关键中脑中心。为了表征成年斑马鱼的 TS，我们使用应用于 TS 和其他相关细胞核和束的碳花青示踪剂研究了它们的连接。两个主要的 TS 核，中央核和腹外侧核，可以通过它们的传入连接来区分。从中央 TS，（TSc）在几个初级八核（前八核、大细胞核、降核和后八核）、次级八核、尾侧八核和肾周区域中标记了许多 toropetal 细胞。在中脑中，对侧 TSc 中标记有大量 toropet 细胞。在间脑中，在同侧内侧前丘脑核和室周后结节核中观察到由 TSc 标记的 toropet 细胞。TSc toropetal 神经元也在下丘脑结节前核（ATN）的双侧和同侧的小细胞视前核中被标记，但在端脑中没有被标记。对内侧八角核的示踪剂应用显示了腹外侧 TS (TSvl) 的对侧投影，而对次级八角核的示踪剂应用则标记了 TSc 中的双侧纤维和头侧 TSc 中的神经元。TSc 将上行纤维发送至同侧外侧肾小球前区域，进而投射至大脑皮层。将 DiI 应用于 TSvl 中的视顶盖标记细胞和纤维，而将 DiI 应用于 TSc 中的 ATN 标记细胞和纤维。这些结果表明，TSvl和TSc主要分别与机械感觉侧线和声学中心相关，并且它们表现出不同的高阶连接。