Blasdel G G, Lund J S
J Neurosci. 1983 Jul;3(7):1389-413. doi: 10.1523/JNEUROSCI.03-07-01389.1983.
We used horseradish peroxidase (HRP) to orthogradely label afferent axons in macaque striate cortex. Of the 38 axons that we recovered, nine were recorded intracellularly before being filled with HRP. Light microscope and computer reconstructions of filled processes reveal highly stereotyped patterns of arborization and suggest that there are at least five discrete populations of lateral geniculate nucleus (LGN) afferent axon: (1) those to layer 4C beta, which have extremely circumscribed, dense terminal fields (small branches of which occasionally intrude into 4C alpha) but which have not been shown to project to other laminae; (2) afferents to layer 4A, which in some cases send fine ascending collaterals into layer 2-3 and which do not, apparently, send collaterals to other laminae; (3) afferents to layer 1, which are fine, extend over large distances horizontally, and send collaterals to layer 6A; (4) afferents to the lower two-thirds of layer 4C alpha, which have few or no collaterals in layer 6; and (5) afferents to the upper half of layer 4C alpha, which have arborizing collaterals in layer 6B. Of the nine axons that were recorded intracellularly, those with projections to layer 4C beta (two axons) and to layer 1 (one axon) had color-selective properties, whereas those (six axons) which arborized in 4C alpha all had transient, broad band and highly contrast-sensitive receptive fields. These properties are consistent with derivations from somata in the parvocellular and magnocellular divisions of the LGN, respectively. Afferents to 4C alpha were found to cover approximately 6 times as much surface area as afferents to 4C beta. The preterminal trunks of all axons were found to follow tortuous paths through the neuropil--paths that may derive from axon segregation during development. The wide ranging, patchy distributions of single afferents in 4C alpha suggest that individual 4C alpha axons supply more than one ocular dominance stripe. In one case where the terminal arborization of a 4C alpha axon was mapped against the transneuronally determined pattern of ocular dominance, three separate patches of terminal boutons were indeed found to coincide with the bands of one eye.
我们使用辣根过氧化物酶（HRP）对猕猴纹状皮层中的传入轴突进行正向标记。在我们回收的38条轴突中，有9条在充满HRP之前进行了细胞内记录。对填充过程的光学显微镜和计算机重建显示出高度刻板的分支模式，并表明至少有五个不同的外侧膝状体核（LGN）传入轴突群体：（1）投射到4Cβ层的轴突，其终末场极其局限且密集（其小分支偶尔侵入4Cα层），但尚未显示投射到其他层；（2）投射到4A层的传入轴突，在某些情况下会向2 - 3层发出细小的上升侧支，显然不会向其他层发出侧支；（3）投射到1层的传入轴突，很细，在水平方向上延伸很长距离，并向6A层发出侧支；（4）投射到4Cα层下三分之二的传入轴突，在6层中几乎没有或没有侧支；（5）投射到4Cα层上半部分的传入轴突，在6B层中有分支侧支。在进行细胞内记录的9条轴突中，投射到4Cβ层的轴突（2条）和投射到1层的轴突（1条）具有颜色选择性特性，而在4Cα层中分支的轴突（6条）都具有瞬态、宽带且高度对比敏感的感受野。这些特性分别与LGN小细胞和大细胞分区中的胞体派生特性一致。发现投射到4Cα层的传入轴突覆盖的表面积约为投射到4Cβ层的传入轴突的6倍。发现所有轴突的终末前干在神经毡中沿着曲折的路径走行——这些路径可能源于发育过程中的轴突分离。4Cα层中单个传入轴突广泛且分散的分布表明，单个4Cα轴突为不止一个眼优势带提供输入。在一个案例中，将一条4Cα轴突的终末分支与经跨神经元确定的眼优势模式进行映射，确实发现三个独立的终末小体斑块与一只眼的带区重合。
