Bruce L L, Stein B E
Department of Anatomy, School of Medicine, Creighton University, Omaha, Nebraska 68178.
J Comp Neurol. 1988 Dec 8;278(2):287-302. doi: 10.1002/cne.902780211.
The postnatal maturation of the projection from the lateral geniculate nucleus to the posteromedial lateral suprasylvian visual cortex (PMLS) was studied with injections of fluorescent dyes into the PMLS at various postnatal ages. Labeled neurons projecting to the PMLS were present in all laminae of the ipsilateral lateral geniculate on the day of birth. However, there was a conspicuous change in the distribution of labeled geniculo-PMLS neurons by 11 days of age: now very few labeled neurons were present in lamina A, indicating a loss of geniculo-PMLS connections. The loss of connections began at the peripheral margins of lamina A and proceeded through other laminae toward laminae C1-3. By adulthood, labeled geniculo-PMLS neurons were largely confined to laminae C1-3; they were never observed in lamina A or A1 and were rarely observed in lamina C. To determine whether the lateral geniculate neurons survived after their projections to PMLS were lost, injections of fast blue were made at 1 or 2 days postnatally and the animals were allowed long postinjection survival times. Labeled neurons were found in all lateral geniculate laminae, thereby indicating that for many neurons the loss of connections could be attributed to a loss of their axon collaterals rather than to the death of the neurons themselves. After injections of fast blue into the PMLS and diamidino yellow dihydrochloride into area 17 shortly after birth, many double-labeled neurons were present in all laminae, indicating that they have collaterals to both targets. Thus, the survival of many of the geniculo-PMLS neurons contributing to the transient geniculo-PMLS projection seems to be due to sustaining collateral projections to area 17 or other cortical targets.
通过在不同出生后年龄段向外侧上薛氏回后内侧视觉皮层（PMLS）注射荧光染料，研究了从外侧膝状体核到PMLS的投射在出生后的成熟过程。出生当天，同侧外侧膝状体的所有层中均存在投射至PMLS的标记神经元。然而，到11日龄时，标记的膝状体 - PMLS神经元的分布发生了显著变化：此时A层中标记神经元很少，表明膝状体 - PMLS连接丧失。连接丧失始于A层的周边边缘，并通过其他层向C1 - 3层发展。到成年时，标记的膝状体 - PMLS神经元主要局限于C1 - 3层；在A层或A1层从未观察到它们，在C层也很少观察到。为了确定外侧膝状体神经元在其到PMLS的投射丧失后是否存活，在出生后1或2天注射快蓝，并让动物在注射后有较长的存活时间。在外侧膝状体的所有层中都发现了标记神经元，从而表明对于许多神经元来说，连接丧失可归因于其轴突侧支的丧失，而非神经元自身的死亡。在出生后不久向PMLS注射快蓝并向17区注射二盐酸双脒基黄后，所有层中都存在许多双标记神经元，表明它们有侧支至两个靶区。因此，许多对短暂的膝状体 - PMLS投射有贡献的膝状体 - PMLS神经元的存活似乎是由于维持了至17区或其他皮质靶区的侧支投射。
