Rosa M G, Schmid L M, Pettigrew J D
Department of Physiology and Pharmacology, University of Queensland, Australia.
Cereb Cortex. 1994 Jan-Feb;4(1):52-68. doi: 10.1093/cercor/4.1.52.
The organization of peristriate cortex was studied in nine flying foxes (genus Pteropus). Based on receptive field mapping and architectonic data, we report on the organization of the second visual area (V2). V2 forms a continuous belt 2-4 mm wide bordering V1 anteriorly. In each hemisphere, V2 contains a precisely organized representation of the entire contralateral visual field. The vertical meridian of the visual field (VM), and a short strip of the ipsilateral hemifield are represented at the posterior border of V2, with V1. The area centralis is represented approximately at the center of the posterior border of V2. At each mediolateral level, progressively more peripheral portions of the visual field are represented as V2 is crossed from posterior to anterior. The representation of the upper quadrant is continuous, and confined to the lateral half of V2. In contrast, the representation of the lower quadrant is split along a line running from the temporal edge of the field of vision to the optic disk. As a result of this arrangement, the portions of the lower quadrant close to the VM are represented medially, and those away from the VM laterally in V2. The entire representation of the horizontal meridian is located in lateral V2, and is not split between medial and lateral V2 as in primates. The linear cortical magnification factor (CMF) decays by a factor of 3-5 from the central to the peripheral representation. The CMF is anisotropic, and equal distances in the visual field are magnified twice as much parallel to the V1/V2 border than perpendicular to this border. Moreover, points in the lower quadrant are magnified relative to symmetrical points in the upper quadrant. V2 is histologically distinct from all surrounding areas in both cytochrome oxidase- and Nissl-stained sections. These results suggest that V2 is an homologous area common to all archontans, and imply that much of the variability reported among mammals may be due to technical factors, rather than true species differences.
在九只狐蝠（狐蝠属）中研究了纹状旁皮质的组织构造。基于感受野图谱绘制和结构数据，我们报告了第二视觉区（V2）的组织构造情况。V2形成一条宽2 - 4毫米的连续带，位于V1前方与之相邻。在每个半球中，V2包含对整个对侧视野的精确组织化表征。视野的垂直子午线（VM）以及同侧半视野的一小条区域在V2的后边界与V1处呈现。中央凹大约在V2后边界的中心处呈现。在每个内外侧层面，随着从后向前穿过V2，视野中逐渐更外周的部分被呈现出来。上象限的表征是连续的，且局限于V2的外侧半部分。相比之下，下象限的表征沿着一条从视野颞侧边缘延伸至视盘的线被分开。由于这种排列方式，下象限中靠近VM的部分在V2中在内侧呈现，而远离VM的部分在外侧呈现。水平子午线的整个表征位于V2外侧，不像灵长类动物那样在内侧V2和外侧V2之间分开。线性皮质放大因子（CMF）从中央表征到外周表征衰减3 - 5倍。CMF是各向异性的，视野中相等的距离在平行于V1/V2边界方向上的放大倍数是垂直于该边界方向上的两倍。此外，下象限中的点相对于上象限中对称的点被放大。在细胞色素氧化酶染色和尼氏染色切片中，V2在组织学上与所有周围区域都不同。这些结果表明V2是所有灵长总目的同源区域，并暗示哺乳动物中报道的许多变异性可能是由于技术因素，而非真正的物种差异。
