Roth G, Dicke U, Grunwald W
Brain Research Institute, Center for Cognitive Sciences, University of Bremen, Germany.
J Comp Neurol. 1999 Feb 22;404(4):489-504. doi: 10.1002/(sici)1096-9861(19990222)404:4<489::aid-cne6>3.0.co;2-0.
In the plethodontid salamanders Plethodon jordani and P. glutinosus, the morphology and axonal projections of 140 tectal neurons and their responses to electrical optic nerve stimulation were determined by intracellular recording and biocytin labeling. Six types of neurons are distinguished morphologically. TO1 neurons have wide dendritic trees that arborize mainly in tectal layers 1 and 3; they project bilaterally to the tegmentum and contralaterally to the medulla oblongata. TO2 neurons have very wide dendritic trees that arborize mainly in layers 2 and 3; axons project bilaterally or unilaterally to the pretectum and thalamus and ipsilaterally to the medulla oblongata. TO3 neurons have very wide and flat dendritic trees confined to layers 3-5; some have the same axonal projection as TO2 neurons, whereas others have descending axons that reach only the level of the cerebellum. TO4 neurons have narrower dendritic trees that arborize in layers 2 and 3; they project to the ipsilateral pretectum, thalamus, and medulla oblongata. TO5 neurons have dendritic trees that arborize in layers 1 and 2 or 1-3 and project bilaterally or unilaterally to the pretectum and thalamus. TO-IN are interneurons, with a number of subtypes with respect to variations in dendritic arborization pattern. TO1-TO5 neurons generally have short latencies of 2-16 ms (average = 8.4 ms) at electrical optic nerve stimulation; first responses are always excitatory, often followed by inhibition. They are likely to be mono- or oligosynaptically driven by retinal afferents. TO-IN interneurons have long latencies of 20-80 ms (average = 38.6 ms) and appear to receive no direct retinal input. With their specific dendritic arborization, consequent dominant retinal input, specific axonal projections, the different types of tectal projection neurons constitute separate ascending and descending visual pathways. Hypotheses are presented regarding the nature of the information processed by these pathways.
在无肺螈科蝾螈红背无肺螈（Plethodon jordani）和黏无肺螈（P. glutinosus）中，通过细胞内记录和生物素标记，确定了140个顶盖神经元的形态、轴突投射及其对视神经电刺激的反应。在形态上可区分出六种类型的神经元。TO1神经元具有广泛的树突树，主要在顶盖的第1层和第3层分支；它们双侧投射到被盖，对侧投射到延髓。TO2神经元具有非常广泛的树突树，主要在第2层和第3层分支；轴突双侧或单侧投射到顶盖前区和丘脑，同侧投射到延髓。TO3神经元具有非常宽且扁平的树突树，局限于第3 - 5层；一些与TO2神经元具有相同的轴突投射，而另一些具有仅到达小脑水平的下行轴突。TO4神经元具有较窄的树突树，在第2层和第3层分支；它们投射到同侧顶盖前区、丘脑和延髓。TO5神经元的树突树在第1层和第2层或第1 - 3层分支，双侧或单侧投射到顶盖前区和丘脑。TO - IN是中间神经元，根据树突分支模式的变化有多种亚型。在视神经电刺激时，TO1 - TO5神经元的潜伏期一般较短，为2 - 16毫秒（平均 = 8.4毫秒）；首次反应总是兴奋性的，随后常伴有抑制。它们可能由视网膜传入纤维单突触或多突触驱动。TO - IN中间神经元的潜伏期较长，为20 - 80毫秒（平均 = 38.6毫秒），似乎没有直接的视网膜输入。凭借其特定的树突分支、随之而来的主要视网膜输入、特定的轴突投射，不同类型的顶盖投射神经元构成了独立的上行和下行视觉通路。文中提出了关于这些通路所处理信息性质的假设。
