Striedter G F, Northcutt R G
Department of Neurosciences, University of California, San Diego, La Jolla 92093.
J Comp Neurol. 1989 May 15;283(3):342-54. doi: 10.1002/cne.902830304.
The connections of the superficial pretectum and of nucleus isthmi were examined in a percomorph teleost, Lepomis cyanellus. Horseradish peroxidase was injected either with a pin into the parvicellular nucleus of the superficial pretectum or pressure injected into nucleus isthmi; the isthmal injections retrogradely labelled the neurons of the magnocellular nucleus of the superficial pretectum. Two main visual pathways can be recognized: The first projects from the retina to the parvicellular nucleus, and then to the intermediate nucleus of the superficial pretectum, the inferior raphe nucleus, and the trochlear nucleus. The second projects from the retina via the optic tectum to the magnocellular nucleus of the superficial pretectum, and from there to nucleus isthmi and the lateral thalamic nucleus; nucleus isthmi and the lateral thalamic nucleus project back to the optic tectum, and nucleus isthmi also projects back to the magnocellular nucleus. The two pathways are interconnected to some extent because both nucleus isthmi and the optic tectum project to the parvicellular nucleus; nevertheless, we suggest that they may be functionally and evolutionarily distinct. Compared to percomorphs, the first pathway appears reduced in cyprinid teleosts such as goldfish. Furthermore, the magnocellular nucleus of the second pathway is completely different in cyprinids, both in cellular architecture and in efferent connections. A phylogenetic analysis suggests that cyprinid ancestors went through a period of reduced vision and that the magnocellular nucleus of the superficial pretectum in modern cyprinids has been either extensively modified from the primitive condition or lost entirely and replaced by a superficially similar structure.
在一种鲈形目硬骨鱼——蓝鳃太阳鱼（Lepomis cyanellus）中，研究了浅顶盖前区和峡核的连接。用针将辣根过氧化物酶注射到浅顶盖前区的小细胞核中，或将其通过压力注射到峡核中；峡核注射逆向标记了浅顶盖前区大细胞核的神经元。可识别出两条主要的视觉通路：第一条从视网膜投射到小细胞核，然后到浅顶盖前区的中间核、中缝下核和滑车神经核。第二条从视网膜经视顶盖投射到浅顶盖前区的大细胞核，再从那里投射到峡核和外侧丘脑核；峡核和外侧丘脑核投射回视顶盖，峡核也投射回大细胞核。这两条通路在一定程度上相互连接，因为峡核和视顶盖都投射到小细胞核；然而，我们认为它们在功能和进化上可能是不同的。与鲈形目鱼类相比，在金鱼等鲤科硬骨鱼中，第一条通路似乎有所减少。此外，第二条通路的大细胞核在鲤科鱼类中完全不同，无论是细胞结构还是传出连接。系统发育分析表明，鲤科鱼类的祖先经历了一段视力下降的时期，现代鲤科鱼类浅顶盖前区的大细胞核要么是从原始状态经过广泛修饰，要么是完全丧失并被一个表面相似的结构所取代。
