Blasdel G G, Lund J S, Fitzpatrick D
J Neurosci. 1985 Dec;5(12):3350-69. doi: 10.1523/JNEUROSCI.05-12-03350.1985.
We have exploited a technique for making small injections of horseradish peroxidase into single cortical laminae in order to study axonal projections in macaque striate cortex. In the preceding paper (Fitzpatrick, D., J. S. Lund, and G. G. Blasdel (1985) J. Neurosci. 5: 3329-3349) we examined the projections of cells in lamina 4C--cells that receive most of their input from the lateral geniculate nucleus. The present paper deals with the projections of neurons that lie outside of lamina 4C. Among our findings are several projections that previously had not been described in the monkey. These include: a strong and precise (point-to-point) projection from lamina 4B to lamina 2/3A, a reciprocal projection from 2/3A back to 4B, a definite projection from lamina 4B to 5B, as well as a prominent input to lamina 6 from 5B. In many cases, we find it possible to trace the flow of visual information through several "circuits" in striate cortex that have, as their output, projections to extrastriate cortex or to the brainstem. Our results offer additional insights in this regard since we are able, in many cases, to compare the lateral spreads of particular projections. These vary and can be separated into at least three categories: those that terminate in a precise, point-to-point, fashion, those that spread widely, and those that terminate in a laterally periodic fashion. In several cases we find evidence for a correlation between specific patterns of projection and known physiological differences between the topographies of laminae that are connected. In cases where two laminae possess similar topographies (for example, where both contain orderly maps for orientation) their interconnections appear precise, with little diffuse spread. In cases where two laminae are characterized by strikingly different topographies (where, for example, one contains an orderly map for orientation and the other a precise map for retinotopic position, but no specificity for orientation), the connections appear more diffuse.
我们采用了一种向单个皮质层小剂量注射辣根过氧化物酶的技术，以研究猕猴纹状皮质中的轴突投射。在前一篇论文中（菲茨帕特里克，D.，J. S. 伦德，和 G. G. 布拉斯德尔（1985年）《神经科学杂志》5: 3329 - 3349），我们研究了4C层细胞的投射——这些细胞大部分输入来自外侧膝状体核。本文探讨位于4C层之外的神经元的投射。我们的发现包括一些先前在猴子身上未被描述过的投射。这些包括：从4B层到2/3A层的强而精确（点对点）的投射、从2/3A层到4B层的相互投射、从4B层到5B层的明确投射，以及从5B层到6层的显著输入。在许多情况下，我们发现有可能追踪视觉信息在纹状皮质中的几个“回路”中的流动，这些回路的输出是投射到纹外皮质或脑干。我们的结果在这方面提供了更多见解，因为在许多情况下，我们能够比较特定投射的横向扩散。这些扩散各不相同，至少可分为三类：以精确点对点方式终止的、广泛扩散的、以横向周期性方式终止的。在几个案例中，我们发现了投射的特定模式与相连层的已知生理差异之间存在相关性的证据。在两层具有相似拓扑结构的情况下（例如，两层都包含有序的方向图），它们的互连显得精确，几乎没有扩散。在两层具有显著不同拓扑结构的情况下（例如，一层包含有序的方向图，另一层包含精确的视网膜拓扑位置图，但对方向无特异性），连接显得更分散。
