Malach R, Tootell R B, Malonek D
Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Cereb Cortex. 1994 Mar-Apr;4(2):151-65. doi: 10.1093/cercor/4.2.151.
Area V2, the main target of primary visual cortex projections, is characterized by a striking functional and connectional compartmentalization. Many aspects of this organization are correlated to three sets of stripes (thick, thin, and pale) revealed by cytochrome oxidase (CO) staining. Several questions related to the physiological properties of these compartments, their intrinsic connections, and points of similarity with area V1 modules are still unresolved. We have addressed some of these questions by combining the techniques of optical imaging of intrinsic signals, tract tracing, and CO histochemistry in the same patches of areas V1 and V2 of the squirrel monkey. The following observations were made. Orientation domains: in area V1 these are organized in narrow bands, while in area V2 they form patches. In area V2, domain width and distance between domains are approximately double that found in area V1. Orientation and CO stripe organization: orientation tuning was organized so that highly selective regions were centered on thick CO stripes while regions of broad orientation selectivity were centered on thin CO stripes. However, the orientation domains appeared to ignore borders between thick and pale stripes. Intrinsic connections: injections of the sensitive tracer biocytin into area V2 labeled a dense network of horizontally projecting fibers that were organized in columnar patches. Patches were small (mean width, 211 microns; mean length, 342 microns) and the labeling pattern extended over 4-5 mm. Axonal patches and CO stripes: Axonal patches found were in all three stripe compartments. However, injections that straddled the borders of thick/pale stripe compartments produced axonal projections that tended to cluster around border regions. Axonal patches and orientation domains: V2 injections produced labeling in V1 that appeared to be organized in narrow bands, reminiscent of orientation domain distribution in V1. Within area V2, axonal patches targeted a wide range of orientation domains, but appeared to avoid domains having orthogonal orientation preference to that found at the injection site. To conclude, our results show, on the one hand, a measure of functional specificity for the CO stripes and the intrinsic connections. On the other hand, they indicate additional substructures within area V2, whose precise relationship to the known compartmental organization remains to be clarified.
V2区是初级视皮层投射的主要目标，其特点是具有显著的功能和连接分区。这种组织的许多方面与细胞色素氧化酶（CO）染色显示的三组条纹（粗条纹、细条纹和淡条纹）相关。与这些分区的生理特性、它们的内在连接以及与V1区模块的相似点相关的几个问题仍未得到解决。我们通过在松鼠猴的V1区和V2区的相同区域结合内在信号光学成像、束路追踪和CO组织化学技术，解决了其中一些问题。得到了以下观察结果。方向域：在V1区，它们以窄带形式组织，而在V2区，它们形成斑块。在V2区，域宽度和域之间的距离大约是V1区的两倍。方向和CO条纹组织：方向调谐的组织方式是，高选择性区域以粗CO条纹为中心，而宽方向选择性区域以细CO条纹为中心。然而，方向域似乎忽略了粗条纹和淡条纹之间的边界。内在连接：将敏感示踪剂生物素注入V2区，标记出一个由水平投射纤维组成密集网络，这些纤维以柱状斑块形式组织。斑块很小（平均宽度211微米；平均长度342微米），标记模式延伸超过4 - 5毫米。轴突斑块和CO条纹：发现的轴突斑块存在于所有三个条纹分区中。然而，跨越粗/淡条纹分区边界的注射产生的轴突投射倾向于聚集在边界区域周围。轴突斑块和方向域：向V2区注射在V1区产生的标记似乎以窄带形式组织，让人联想到V1区的方向域分布。在V2区内，轴突斑块针对广泛的方向域，但似乎避开与注射部位方向偏好正交的域。总之，我们的结果一方面显示了CO条纹和内在连接的一定程度的功能特异性。另一方面，它们表明V2区内还有其他亚结构，其与已知分区组织的确切关系仍有待阐明。
