Malpeli J G, Lee D, Baker F H
Department of Psychology, University of Illinois, Champaign 61820, USA.
J Comp Neurol. 1996 Nov 18;375(3):363-77. doi: 10.1002/(SICI)1096-9861(19961118)375:3<363::AID-CNE2>3.0.CO;2-0.
The laminar morphology and electrophysiologically determined retinotopic organization of a single rhesus macaque lateral geniculate nucleus (LGN) were reconstructed on series of coronal, sagittal, and horizontal cuts through a three-dimensional computer representation of the nucleus. Neurons were counted in this same nucleus, allowing the magnification functions (cells/degree2 as functions of eccentricity) of magnocellular and parvocellular layers to be determined after eliminating the effects of nonuniform volume shrinkage. Parvocellular magnification was approximately 10,000 times higher in the foveola than in the far periphery. On average, magnocellular neurons made up 2.6% of the LGN in the central 2 degrees (but probably a smaller fraction in the central fovea). The magnocellular portion increased steadily with eccentricity to 27% in the far periphery. Thus the magno/parvo ratio increases from foveola to far periphery by a factor of at least 14. The parvocellular magnification function matches estimates of cortical magnification, whereas the density of magnocellular afferents to cortex increases monotonically with eccentricity. At the posterior pole of the nucleus, the numbers of layers are reduced through a fusion of two layers and the disappearance of one or two others, a feature that may be associated with the foveal ipsilateral hemifield representation.
通过对恒河猴外侧膝状核（LGN）的三维计算机模型进行一系列冠状、矢状和水平切割，重建了单个恒河猴外侧膝状核的层状形态和通过电生理确定的视网膜拓扑组织。在同一个核中对神经元进行计数，在消除不均匀体积收缩的影响后，确定了大细胞层和小细胞层的放大功能（细胞数/度²作为离心率的函数）。小细胞在中央小凹处的放大倍数比在远周边处大约高10000倍。平均而言，大细胞神经元在中央2度范围内占外侧膝状核的2.6%（但在中央小凹处可能占比更小）。大细胞部分随着离心率的增加而稳步增加，在远周边处达到27%。因此，大细胞/小细胞比例从中央小凹到远周边至少增加了14倍。小细胞放大功能与皮质放大的估计值相匹配，而皮质的大细胞传入纤维密度则随着离心率单调增加。在核的后极，通过两层融合以及另外一到两层的消失，层数减少，这一特征可能与中央小凹同侧半视野的表征有关。
