Connolly M, Van Essen D
J Comp Neurol. 1984 Jul 10;226(4):544-64. doi: 10.1002/cne.902260408.
Two-dimensional maps of individual layers of the dorsal lateral geniculate nucleus (LGN) in the macaque monkey were constructed and used as a basis for comparing laminar size, shape, and topographic organization. Topographical data from the electrophysiological investigation of the LGN by Malpeli and Baker ('75) were displayed on maps of all six layers. As known from previous studies, there is a significant over-representation of central vision in the LGN. Unexpectedly, though, the visual representation is anisotropic over portions of most LGN layers. That is, the linear magnification factor (millimeters along the laminar surface per degree of visual field) is not equal for all directions from a given point in the visual field. Moreover, the visual representations in the parvicellular and magnocellular divisions of the LGN differ both in their emphasis on central vision and in their anisotropies. To determine the degree of individual variability, laminar maps were prepared from the LGN of seven other hemispheres. The shapes of laminar maps varied considerably between LGNs, from nearly circular to highly elliptical, but the surface area was relatively constant for each layer. Topographical organization, determined by mapping the optic disc representation on the LGN laminae and by labeling from anterograde and retrograde tracer injections in striate cortex, showed significant individual variability. Interestingly, the visual representations in the LGN and striate cortex are topologically inverted with respect to one another. This indicates that the establishment of geniculocortical connections involves a systematic crossing-over of fibers. Information on cell densities and magnification factors in striate cortex obtained from other studies was compared to the results of the present study in order to estimate ratios of cortical neurons to LGN neurons at different eccentricities. The total number of cortical neurons per LGN neuron is about 130 on average, but it extends over approximately a tenfold range, from less than 100 in the far periphery to nearly 1,000 in the fovea. The estimated number of cells in layers 4A and 4C beta per parvicellular layer neuron is smaller and extends over a slightly narrower range, from 30 to 240, whereas the number of layer 4C alpha neurons per magnocellular neuron varies more widely, from about 45 to 7,000.
构建了猕猴背外侧膝状核（LGN）各层的二维图谱，并以此为基础比较各层的大小、形状和地形组织。马尔佩利和贝克（1975年）对LGN进行电生理研究得到的地形数据显示在所有六层的图谱上。如先前研究所知，LGN中存在显著的中央视觉过度表征。然而，出乎意料的是，在大多数LGN层的部分区域，视觉表征是各向异性的。也就是说，线性放大因子（沿层表面每度视野的毫米数）对于视野中给定点的所有方向并不相等。此外，LGN的小细胞和大细胞分区中的视觉表征在对中央视觉的强调以及各向异性方面都有所不同。为了确定个体变异性的程度，从其他七个半球的LGN制备了层图谱。层图谱的形状在不同的LGN之间差异很大，从近乎圆形到高度椭圆形，但每层的表面积相对恒定。通过在LGN层上绘制视盘表征以及通过在纹状皮层中进行顺行和逆行示踪剂注射标记来确定的地形组织显示出显著的个体变异性。有趣的是，LGN和纹状皮层中的视觉表征在拓扑结构上彼此相反。这表明膝状体皮质连接的建立涉及纤维的系统性交叉。将其他研究中获得的纹状皮层中细胞密度和放大因子的信息与本研究的结果进行比较，以估计不同偏心度下皮质神经元与LGN神经元的比例。每个LGN神经元的皮质神经元总数平均约为130，但范围约为十倍，从远周边的不到100到中央凹的近1000。每个小细胞层神经元在4A层和4Cβ层中的估计细胞数较少，范围稍窄，从30到240，而每个大细胞神经元的4Cα层神经元数变化更大，从约45到7000。
