Kossel A, Löwel S, Bolz J
Friedrich-Miescher Labor der Max-Planck Gesellschaft, Tübingen, Germany.
J Neurosci. 1995 May;15(5 Pt 2):3913-26. doi: 10.1523/JNEUROSCI.15-05-03913.1995.
We examined relationships between the pattern of geniculocortical innervation and the dendritic fields of cells in layer 4 of in cat primary visual cortex. Experiments were performed on normal animals and on cats in which the geniculocortical projection was altered by monocular deprivation or by the induction of divergent squint during the critical period. Thalamic afferents providing the input from the contralateral eye were anterogradely labeled by injecting the fluorescent tracer Dil into lamina A of the lateral geniculate nucleus. Intracellular staining with Lucifer yellow in slice preparations allowed simultaneous visualization of the morphology of individual cells and the thalamic afferents. Our results demonstrate that spiny stellate cells close to the upper and lower margin of the geniculocortical input have highly asymmetric dendritic fields, and thereby confine their dendrites to the termination zone of these afferents. This effect was specific for the cell class; it was not observed in pyramidal neurons. These dendritic asymmetries perpendicular to the laminar borders of spiny stellate cells were not altered by monocular deprivation or strabismus. In contrast, visual deprivation strongly influenced the dendritic arbors of spiny stellate cells near the borders between adjacent ocular dominance columns. In normal animals, the dendrites of cells near columnar borders remained preferentially within one column. These dendritic asymmetries became much more pronounced in strabismic animals. Monocular deprivation weakened the influence of the columnar borders on dendritic fields. Spiny stellate cells within the columns of the open eye exhibited a slight tendency to confine their dendrites to these columns. Cells in the columns of the deprived eye showed the opposite effect; they extended their dendrites preferentially into the adjacent columns of the open eye. These results demonstrate that the segregation of geniculocortical afferents into ocular dominance columns and its perturbation by manipulation of the visual input plays an important role in defining the morphology of cortical target cells. Thus, activity-dependent structural changes not only occur at the level of the presynaptic terminals, but also at the level of the postsynaptic target cells, and thereby contribute to build up the functional architecture of the cortex.
我们研究了猫初级视觉皮层第4层细胞的膝状体皮质神经支配模式与树突野之间的关系。实验在正常动物以及在关键期通过单眼剥夺或诱发散开性斜视改变了膝状体皮质投射的猫身上进行。通过将荧光示踪剂Dil注入外侧膝状体核的A层，对提供来自对侧眼输入的丘脑传入纤维进行顺行标记。在脑片制备中用路西法黄进行细胞内染色，可同时观察单个细胞的形态和丘脑传入纤维。我们的结果表明，靠近膝状体皮质输入上下边缘的棘状星状细胞具有高度不对称的树突野，从而将其树突局限于这些传入纤维的终止区。这种效应对于细胞类型具有特异性；在锥体细胞中未观察到。这些垂直于棘状星状细胞层状边界的树突不对称性不受单眼剥夺或斜视的影响。相比之下，视觉剥夺强烈影响了相邻眼优势柱边界附近棘状星状细胞的树突分支。在正常动物中，柱边界附近细胞的树突优先保留在一个柱内。这些树突不对称性在斜视动物中变得更加明显。单眼剥夺减弱了柱边界对树突野的影响。睁眼柱内的棘状星状细胞有将其树突局限于这些柱内的轻微倾向。剥夺眼柱内的细胞表现出相反的效应；它们的树突优先延伸到睁眼的相邻柱内。这些结果表明，膝状体皮质传入纤维分离为眼优势柱以及通过视觉输入操作对其的扰动在定义皮质靶细胞的形态中起重要作用。因此，依赖活动的结构变化不仅发生在突触前终末水平，也发生在突触后靶细胞水平，从而有助于构建皮质的功能结构。
