Adelson P D, Hovda D A, Villablanca J R, Tatsukawa K
Division of Neurosurgery, UCLA School of Medicine 90024-6901, USA.
Brain Res Dev Brain Res. 1995 May 26;86(1-2):81-93. doi: 10.1016/0165-3806(95)00007-z.
A hypothetical mechanism for the partial sparing of visual function in the contralateral visual field following cerebral hemispherectomy early in life is the formation of a new corticotectal pathway arising from the remaining primary visual cortex (areas 17 and 18) that projects to the contralateral superior colliculus. To test this hypothesis, the left superior colliculus of intact adult and neonatal (5-15 days old) cats and of adult cats with a left cerebral hemispherectomy sustained neonatally (7-9 days old) or in adulthood, was injected with WGA-HRP and the brains were processed for combined TMB/DAB histochemistry. The primary visual cortex was examined, labelled neurons were counted and the cross sectional area of their somata was measured. The left primary visual cortex of intact adult animals exhibited a mean of 959.68 labelled cells +/- 406.5 (S.E.), with a mean soma size of 366.7 microns2 +/- 131.2. For the neonatal intact cats, there was a mean of 75.31 +/- 21.08 cells within the left primary visual cortex which exhibited a mean soma size of 249.56 microns2 +/- 68.18. The peak cell size distribution for both intact groups was similar at 300 microns2. Virtually no labelled neurons were detected in the right primary visual cortex of intact animals (neonatal or adult). For neonatal-hemispherectomized cats, the remaining right primary visual cortex exhibited a mean cell count of 351.09 +/- 126.3 cells, with a mean soma size of 436.1 microns2 +/- 131.5, and a peak cell size distribution of 400 microns2. Finally, for adult-hemispherectomized animals, the contralateral primary visual cortex exhibited 68.27 +/- 20.13 neurons having a mean soma size of 486.6 microns2 +/- 143.2 with a peak cell size distribution of 500 microns2. These results indicate that reorganization of the corticotectal pathway occurs in both adult- and neonatal-hemispherectomized cats but is more pronounced in neonatal-lesioned animals. In addition, the cells of origin of this reorganized pathway tended to be larger, perhaps in response to a greater axonal arborization.
一种关于生命早期大脑半球切除术后对侧视野视觉功能部分保留的假设机制是，由剩余的初级视觉皮层（17区和18区）形成一条新的皮质-顶盖通路，该通路投射到对侧上丘。为了验证这一假设，对成年和新生（5 - 15日龄）的完整猫以及新生期（7 - 9日龄）或成年期进行左侧大脑半球切除术的成年猫的左侧上丘注射WGA - HRP，并对大脑进行TMB/DAB联合组织化学处理。检查初级视觉皮层，对标记的神经元进行计数并测量其胞体的横截面积。成年完整动物的左侧初级视觉皮层平均有959.68个标记细胞±406.5（标准误），胞体平均大小为366.7平方微米±131.2。对于新生完整猫，左侧初级视觉皮层内平均有75.31±21.08个细胞，胞体平均大小为249.56平方微米±68.18。两个完整组的细胞大小峰值分布在300平方微米时相似。在成年或新生的完整动物的右侧初级视觉皮层中几乎未检测到标记神经元。对于新生期行半球切除术的猫，剩余的右侧初级视觉皮层平均细胞计数为351.09±126.3个，胞体平均大小为436.1平方微米±131.5，细胞大小峰值分布为400平方微米。最后，对于成年期行半球切除术的动物，对侧初级视觉皮层有68.27±20.13个神经元，胞体平均大小为486.6平方微米±143.2，细胞大小峰值分布为500平方微米。这些结果表明，在成年和新生期行半球切除术的猫中均发生了皮质-顶盖通路的重组，但在新生期损伤的动物中更为明显。此外，这条重组通路的起源细胞往往更大，这可能是对更大的轴突分支的一种反应。
