Sincich Lawrence C, Horton Jonathan C
Beckman Vision Center, University of California, San Francisco, San Francisco, California 94143, USA.
J Comp Neurol. 2002 May 20;447(1):18-33. doi: 10.1002/cne.10174.
Once the visual pathway reaches striate cortex, it fans out to a number of extrastriate areas. The projections to the second visual area (V2) are known to terminate in a patchy manner. V2 contains a system of repeating pale-thin-pale- thick stripes of cytochrome oxidase (CO) activity. We examined whether the patchy terminal fields arising from primary visual cortex (V1) projections are systematically related to the CO stripes in V2. Large injections of an anterograde tracer, [(3)H]proline, were made into V1 of both hemispheres in 5 macaques. The resulting V2 label appeared in layers 2-6, with the densest concentration in layer 4. In 21/29 injections, comparison of adjacent flatmount sections processed either for autoradiography or CO activity showed that the heaviest [(3)H]proline labeling was located in pale CO stripes. In 7/29 injections, there was no clear enrichment of labeling in the CO pale stripes. In 1 injection, the proline label correlated with dark CO stripes. On a fine scale, CO levels vary within V2 stripes, giving them an irregular, mottled appearance. In all stripe types, the density of proline label would often wax and wane in opposing contrast to these local fluctuations in CO density. Our data showed that V1 input is generally anti-correlated with the intensity of CO staining in V2, with strongest input to pale stripes. It is known that the pulvinar projects preferentially to dark stripes. Therefore, V2 receives interleaved projections from V1 and the pulvinar. Because these projections favor different stripe types, they may target separate populations of neurons.
一旦视觉通路到达纹状皮层，它就会扩展到多个纹外区域。已知投向第二视区（V2）的投射以斑片状方式终止。V2包含一个由细胞色素氧化酶（CO）活性的浅色 - 薄 - 浅色 - 厚条纹组成的重复系统。我们研究了源自初级视皮层（V1）投射的斑片状终末场是否与V2中的CO条纹系统相关。在5只猕猴的两个半球的V1中大量注射顺行示踪剂[³H]脯氨酸。在V2中产生的标记出现在第2 - 6层，其中第4层浓度最高。在21/29次注射中，对用于放射自显影或CO活性处理的相邻平铺切片进行比较，结果显示[³H]脯氨酸标记最重的区域位于浅色CO条纹中。在7/29次注射中，CO浅色条纹中没有明显的标记富集。在1次注射中，脯氨酸标记与深色CO条纹相关。在精细尺度上，V2条纹内的CO水平各不相同，使其呈现出不规则的斑驳外观。在所有条纹类型中，脯氨酸标记的密度通常会与CO密度的这些局部波动呈相反的增减变化。我们的数据表明，V1的输入通常与V2中CO染色的强度呈反相关，对浅色条纹的输入最强。已知丘脑枕优先投射到深色条纹。因此，V2接受来自V1和丘脑枕的交错投射。由于这些投射有利于不同的条纹类型，它们可能针对不同的神经元群体。
