Ferrer J M, Price D J, Blakemore C
University Laboratory of Physiology, University of Oxford, U.K.
Proc R Soc Lond B Biol Sci. 1988 Feb 23;233(1270):77-98. doi: 10.1098/rspb.1988.0013.
Retrogradely transported tracers were injected into area 18 of the visual cortex of the adult cat to study the organization of corticocortical projections from area 17 to area 18. All injections, whether very small or relatively large, and irrespective of their exact location in area 18, produced a discontinuous, clustered distribution of labelled cells, mainly in layers II, III and upper IV, in a topographically related region of area 17. The mean centre-centre distance between neighbouring patches was about 750 microns. We conclude that the overall population of cells projecting to area 18 is genuinely distributed in a patchy fashion and that they provide an efficient spatial sample of information from area 17. Comparison of the dimensions of each injection site and of the retrogradely labelled territory suggested that each region in area 18 receives a convergent input from a zone in area 17 whose visual field representation is about 0.8 M-1 deg larger in all directions (where M is the magnification factor in millimetres per degree at the termination site in area 18). Pairs of injection were made in area 18 by placing small volumes of two fluorescent tracers, fast blue and diamidino yellow, side-by-side in either a rostrocaudal or a mediolateral plane, with different distances between them. When the boundaries of the dense central cores of two injection sites were separated, at their closest points, by about 1.6 mm, the two corresponding distributions of labelled cells in area 17 were just non-overlapping, suggesting that each group of cells in area 17 sends a divergent projection in innervate a zone about 0.8 mm larger in all directions in area 18. More closely spaced injections led to overlap of the distributions of labelling by the two dyes, with shared clusters containing a mixture of labelled cells. The proportion of double-labelled cells in these shared clusters never exceeded 4.4% (but was 70% after sequential injection of the two dyes at a single point). We conclude that, although each cluster of cells sends a divergent projection to area 18, the majority of individual axons terminate more discretely, perhaps providing specific inter-connections between functionally corresponding 'columns' in the two areas.
将逆行运输示踪剂注入成年猫视皮层的18区，以研究从17区到18区的皮质皮质投射的组织方式。所有注射，无论非常小还是相对较大，且无论其在18区的确切位置如何，都在17区的一个地形相关区域产生了标记细胞的不连续、成簇分布，主要位于II层、III层和IV层上部。相邻斑块之间的平均中心距约为750微米。我们得出结论，投射到18区的细胞总体确实以斑块状分布，并且它们提供了来自17区的有效空间信息样本。对每个注射部位的尺寸与逆行标记区域的比较表明，18区的每个区域从17区的一个区域接收汇聚输入，该区域的视野表示在各个方向上大约大0.8 M - 1度（其中M是在18区终止部位每度毫米的放大倍数）。通过将少量两种荧光示踪剂（快蓝和二脒基黄）在前后或内外侧平面上并排放置，在18区进行成对注射，它们之间有不同的距离。当两个注射部位密集中心核的边界在最接近点处相隔约1.6毫米时，17区中两个相应的标记细胞分布刚好不重叠，这表明17区中的每组细胞发出发散投射，以支配18区中各个方向大约大0.8毫米的一个区域。间隔更近的注射导致两种染料标记分布的重叠，共享簇中含有混合的标记细胞。这些共享簇中双标记细胞的比例从未超过4.4%（但在同一点顺序注射两种染料后为70%）。我们得出结论，虽然每组细胞向18区发出发散投射，但大多数单个轴突更离散地终止，可能在两个区域中功能对应的“柱”之间提供特定的相互连接。
