Sherk H, Mulligan K A
Department of Biological Structure, University of Washington, Seattle 98195.
Vis Neurosci. 1993 Jan-Feb;10(1):131-58. doi: 10.1017/s0952523800003278.
Lateral suprasylvian visual cortex in the cat has been studied extensively, but its retinotopic organization remains controversial. Although some investigators have divided this region into many distinct areas, others have argued for a simpler organization. A clear understanding of the region's retinotopic organization is important in order to define distinct areas that are likely to subserve unique visual functions. We therefore reexamined the map of the lower visual field in the striate-recipient region of lateral suprasylvian cortex, a region we refer to as the lateral suprasylvian area, LS. A dual mapping approach was used. First, receptive fields were plotted at numerous locations along closely spaced electrode penetrations; second, different anterograde tracers were injected at retinotopically identified sites in area 17, yielding patches of label in LS. To visualize the resulting data, suprasylvian cortex was flattened with the aid of a computer. Global features of the map reported in many earlier studies were confirmed. Central visual field was represented posteriorly, and elevations generally shifted downward as one moved anteriorly. Often (though not always) there was a progression from peripheral locations towards the vertical meridian as the electrode moved down the medial suprasylvian bank. The map had some remarkable characteristics not previously reported in any map in the cat. The vertical meridian's representation was split into two pieces, separated by a gap, and both pieces were partially internalized within the map. Horizontal meridian occupied the gap. The area centralis usually had a dual representation along the posterior boundary of the lower field representation, and other fragments of visual field were duplicated as well. Finally, magnification appeared to change abruptly and unexpectedly, so that compressed regions of representation adjoined expanded regions. Despite its complexity, we found the map to be more orderly than previously thought. There was no clearcut retinotopic basis on which to subdivide LS's lower field representation into distinct areas.
猫的外侧上薛氏视觉皮层已得到广泛研究，但其视网膜拓扑组织仍存在争议。尽管一些研究者将该区域划分为许多不同的区域，但另一些人则主张组织结构更为简单。为了确定可能执行独特视觉功能的不同区域，清楚了解该区域的视网膜拓扑组织很重要。因此，我们重新检查了外侧上薛氏皮层纹状区接受区的下视野图谱，我们将该区域称为外侧上薛氏区（LS）。采用了双重映射方法。首先，沿着紧密间隔的电极穿刺在多个位置绘制感受野；其次，在17区视网膜拓扑定位的位点注射不同的顺行示踪剂，在LS中产生标记斑。为了可视化所得数据，借助计算机将上薛氏皮层展平。许多早期研究报告的图谱的整体特征得到了证实。中央视野在后部呈现，随着向前移动，高度通常向下移动。随着电极沿着内侧上薛氏河岸向下移动，通常（但并非总是）存在从周边位置向垂直子午线的进展。该图谱具有一些先前在猫的任何图谱中均未报道的显著特征。垂直子午线的表征被分成两部分，由一个间隙隔开，并且两部分都部分内化在图谱中。水平子午线占据该间隙。中央凹通常在下视野表征的后边界沿线有双重表征，并且视野的其他片段也有重复。最后，放大倍数似乎突然且出乎意料地发生变化，因此表征的压缩区域与扩展区域相邻。尽管其复杂性，但我们发现该图谱比之前认为的更有序。没有明确的视网膜拓扑基础可将LS的下视野表征细分为不同的区域。
