Reese B E, Cowey A
Department of Human Anatomy, University of Oxford, England.
J Comp Neurol. 1990 May 15;295(3):401-12. doi: 10.1002/cne.902950305.
The representations of the two half-retinae were examined in the monkey's optic tract. Intravitreal injections of tritiated amino acids were made to reveal the distributions of the crossed and uncrossed populations of optic axons, while localized implants of horseradish peroxidase (HRP) were made into different regions of the optic tract in order to examine the distributions and morphological types of retrogradely labelled cells at corresponding loci in the two half-retinae. Crossed and uncrossed optic axons are intermingled throughout most of the optic tract, but uncrossed axons are very sparse or absent along both the deep and superficial extremes of the tract. Implants of HRP into the deeper regions of the tract demonstrate that the crossed and uncrossed optic axons of the P beta retinal ganglion cells are slightly out of binocular registration, with the uncrossed map being shifted to a slightly superficial location relative to the crossed map. The optic axons for the remaining cell classes, revealed by implants of HRP into the superficial portion of the tract, are much more conspicuously out of binocular registration (in particular, the P alpha optic axons); but in their cases, the uncrossed optic axons are shifted to deeper locations relative to the crossed optic axons. Further evidence that these optic axon classes are markedly out of binocular registration comes from the two optic tracts of a bilaterally destriated monkey, in which most of the P beta optic axons have undergone a transneuronal retrograde degeneration. Following a uni-ocular injection of tritiated amino acids, the distributions of the remaining crossed and uncrossed axonal labelling occupied different positions within the tract rather than being intermingled, with the uncrossed optic axons situated deep to the majority of crossed optic axons. These results demonstrate that the optic chiasm does not combine binocularly corresponding optic axons of similar type. They also demonstrate that noncongruent field defects should be a common consequence of damage to the optic tract in humans. If the fibre order in the mammalian optic tract arises as a consequence of the sequence of axonal addition during development, then differences in the relative times of genesis for nasal and temporal members of any cell class, and/or differences in the relative pathlengths between the eye and two optic tracts, may produce the fibre ordering described herein.
在猴子的视束中对视神经两半视网膜的表征进行了研究。通过玻璃体内注射氚标记的氨基酸来揭示视轴突交叉和未交叉群体的分布，同时将辣根过氧化物酶（HRP）局部植入视束的不同区域，以检查两半视网膜相应位点处逆行标记细胞的分布和形态类型。交叉和未交叉的视轴突在视束的大部分区域相互交织，但在视束的深部和浅部极端区域，未交叉的轴突非常稀疏或不存在。将HRP植入视束较深区域表明，Pβ视网膜神经节细胞的交叉和未交叉视轴突略有双眼不对称，未交叉图谱相对于交叉图谱向稍浅的位置偏移。通过将HRP植入视束浅部揭示的其余细胞类别的视轴突，双眼不对称更为明显（特别是Pα视轴突）；但在它们的情况下，未交叉视轴突相对于交叉视轴突向更深的位置偏移。这些视轴突类别明显双眼不对称的进一步证据来自双侧去皮质猴子的两条视束，其中大多数Pβ视轴突经历了跨神经元逆行变性。在单眼注射氚标记的氨基酸后，其余交叉和未交叉轴突标记的分布在视束内占据不同位置，而不是相互交织，未交叉视轴突位于大多数交叉视轴突的深部。这些结果表明，视交叉并没有将相似类型的双眼对应视轴突组合在一起。它们还表明，非一致性视野缺损应该是人类视束损伤的常见后果。如果哺乳动物视束中的纤维顺序是发育过程中轴突添加顺序的结果，那么任何细胞类别的鼻侧和颞侧成员在生成相对时间上的差异，和/或眼睛与两条视束之间相对路径长度的差异，可能会产生本文所述的纤维排序。
