Diamond I T, Conley M, Fitzpatrick D, Raczkowski D
Department of Psychology, Duke University, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1991 Feb 15;88(4):1315-9. doi: 10.1073/pnas.88.4.1315.
Two layers (3 and 6) in the dorsal lateral geniculate nucleus (GLd) of the tree shrew (Tupaia belangeri) receive projections from the superficial layers of the superior colliculus. The goal of this study was to determine whether the same or different cells in the superior colliculus give rise to the projections to layers 3 and 6 by following individual axons labeled with biocytin from the superior colliculus to the GLd. The results show that the terminal fields differ in the two layers--those in layer 3 are restricted to a line of projection, whereas those in layer 6 are elongated along the dimension orthogonal to a line of projection. Another important difference between axons that project to GLd layers 3 and 6 is that those that project to layer 6 give off collaterals to the posterior pretectal nucleus, whereas at least some axons that project to layer 3 send a collateral to the ventral lateral geniculate nucleus (GLv). These results suggest that the superior colliculus exerts separate influences on these two GLd layers, both of which project to separate targets above layer IV in the striate cortex. The biocytin method has proved useful by showing the dendritic trees of the superior colliculus cells of origin, the pathways taken by the axons (including the presence of collaterals), and the terminal fields both within and outside the GLd.
树鼩（笔尾树鼩）背外侧膝状核（GLd）的第3层和第6层接收来自上丘表层的投射。本研究的目的是通过追踪从上丘用生物胞素标记至GLd的单个轴突，来确定上丘中相同或不同的细胞是否产生至第3层和第6层的投射。结果显示，这两层的终末野不同——第3层的终末野局限于一条投射线，而第6层的终末野则沿与投射线正交的维度伸长。投射至GLd第3层和第6层的轴突之间的另一个重要差异是，投射至第6层的轴突会发出侧支至顶盖前区核，而至少一些投射至第3层的轴突会发出一个侧支至腹外侧膝状核（GLv）。这些结果表明，上丘对GLd的这两层施加了不同的影响，这两层都投射至纹状皮层第IV层以上的不同靶区。生物胞素方法已被证明是有用的，它显示了起源的上丘细胞的树突树、轴突所走的路径（包括侧支的存在）以及GLd内外的终末野。
