Montgomery N, Fite K V
Neuroscience and Behavior Program, University of Massachusetts, Amherst 01003.
J Comp Neurol. 1989 May 22;283(4):526-40. doi: 10.1002/cne.902830407.
The retinotopic organization of the anuran visual system has been investigated with the method of selective anterograde transport of horseradish peroxidase (HRP) following retinal lesions. The course of optic axons to specific structures was also confirmed by retrograde transport in the optic tract following HRP injections in the tectum and pretectum. As the optic nerve reaches the optic chiasm, the fibers from each of the four retinal quadrants appear as bands with the nasal (n) quadrant entering the chiasmal anterior pole, followed by ventral (v), temporal (t), and dorsal (d) quadrants. The preoptic nucleus is the first structure to be innervated, followed by the suprachiasmatic nucleus; both are innervated directly from fibers in the dorsal part of the optic nerve, which contains fibers from all the retinal quadrants. Each quadrant expands across the dorsoventral extent of the chiasm at the point where it enters. At this level the quadrants are arrayed along the rostrocaudal axis (as they are later in the marginal optic tract) in the sequence n-v-t-d. Optic fibers then spread across the chiasm, the nasal quadrant splits, taking up positions in the rostral and caudal margins of the optic radiation. Following the split in the nasal representation, the optic tract is transformed into topographically arranged sheets in the marginal optic tract. In the other retinorecipient nuclei, the sheet of optic axons is transformed back into the shape of the retinal hemisphere. Topographic maps of this kind display one of two possible orientations: (1) in the tectum and the nucleus lentiformis mesencephali (nLM), the temporal retina is represented in the anterior portion of the nucleus, whereas the nasal quadrant is found in the posterior portion; (2) in the thalamus, the retinotopic map is organized as a mirror-image reversal of that seen in the tectum and nLM (i.e., the nasal pole is anterior, whereas the temporal pole is in the posterior portion of the nucleus). Structures with this type of retinal map include the rostral visual nucleus, the corpus geniculatum, the nucleus of Bellonci, and the posterior thalamic nucleus. A third type of innervation occurs in the nucleus of the basal optic root (nBOR), which is the only mesencephalic visual nucleus not innervated by the marginal optic tract. The basal optic root is formed by the fibers exiting most caudally from the optic chiasm. All the retinal quadrants contribute to the basal optic root, but no evidence of retinotopy was found in nBOR.4+ target nuclei.
通过视网膜损伤后辣根过氧化物酶（HRP）选择性顺行运输的方法，对无尾目视觉系统的视网膜定位组织进行了研究。在顶盖和顶盖前区注射HRP后，通过视束中的逆行运输也证实了视神经向特定结构的走行。当视神经到达视交叉时，来自四个视网膜象限的纤维呈现为带状，鼻侧（n）象限进入视交叉的前极，随后是腹侧（v）、颞侧（t）和背侧（d）象限。视前核是第一个被支配的结构，其次是视交叉上核；两者都直接由视神经背侧部分的纤维支配，该部分包含来自所有视网膜象限的纤维。每个象限在进入视交叉的点处横跨视交叉的背腹范围扩展。在这个水平上，象限沿着前后轴排列（就像它们后来在边缘视束中那样），顺序为n-v-t-d。然后，视神经纤维在视交叉上扩散，鼻侧象限分开，占据视辐射的前后边缘位置。在鼻侧代表区分开后，视束在边缘视束中转变为按地形排列的薄片。在其他视网膜接受核中，视神经轴突薄片又变回视网膜半球的形状。这种类型的地形图显示出两种可能的方向之一：（1）在顶盖和中脑豆状核（nLM）中，颞侧视网膜在核的前部代表，而鼻侧象限在后部；（2）在丘脑中，视网膜定位图的组织方式与顶盖和nLM中的相反（即，鼻极在前，而颞极在核的后部）。具有这种视网膜图类型的结构包括前视觉核、外侧膝状体、贝隆奇核和丘脑后核。第三种类型的支配发生在基底视神经核（nBOR），它是唯一未被边缘视束支配的中脑视觉核。基底视神经根由从视交叉最尾端发出的纤维形成。所有视网膜象限都对视神经根有贡献，但在nBOR中未发现视网膜定位的证据。4个目标核。
