Fitzpatrick D, Lund J S, Blasdel G G
J Neurosci. 1985 Dec;5(12):3329-49. doi: 10.1523/JNEUROSCI.05-12-03329.1985.
We have studied the intrinsic organization of macaque striate cortex by tracing the pattern of horseradish peroxidase (HRP)-labeled axons and cell bodies produced by microinjections of HRP into single cortical laminae. Both anterograde and retrograde transport results were used to examine: (1) the pattern of projections from lamina 4C to the superficial layers; (2) the projection from lamina 4C to deeper cortical layers; and (3) the projections to lamina 4C from other cortical laminae. Laminae 4C alpha and 4C beta differ in their pattern of projections to the superficial layers of striate cortex. Axons from neurons in lamina 4C beta ascend through lamina 4B without giving off collaterals and terminate in lamina 4A and in the base of lamina 3. By contrast, axons from neurons in lamina 4C alpha terminate in lamina 4B and less densely in the 4A/3B region. The projection from lamina 4C beta to lamina 4A is particularly dense and is distributed in a patchy fashion immediately above each injection site. The projection from lamina 4C beta to lamina 3B appears less dense and more widespread; we estimate that individual 4C beta axons may spread laterally for more than 400 micron. Furthermore, the pattern of HRP-labeled cell bodies in lamina 4C beta following injections into laminae 4A and 3B provides evidence for a subdivision within 4C beta. These injections always produce a large number of labeled neurons in the upper part of lamina 4C beta, whereas the lower portion contains few labeled neurons that are located immediately under the center of the injection site. Both lamina 4C alpha and lamina 4C beta also contribute less dense projections to the deeper layers of cortex. Lamina 4C beta projects mainly to lamina 6, whereas lamina 4C alpha contributes axon terminals to both lamina 5A and lamina 6. Neurons in lamina 6 provide the bulk of the intracortical projections to lamina 4C. The axons of these neurons are fine in caliber and have a delicate side-spine morphology that is quite distinct from lateral geniculate axon arbors. Neurons in lamina 5A also project onto lamina 4C, but the projections of these neurons appear concentrated in lamina 4C alpha. These results confirm or refine many conclusions about intrinsic connections of striate cortex drawn from Golgi material and suggest new patterns of connections not suspected from previous work.
我们通过追踪将辣根过氧化物酶（HRP）显微注射到单个皮质层后所产生的HRP标记轴突和细胞体的模式，研究了猕猴纹状皮质的内在组织。顺行和逆行运输结果均用于研究：（1）从4C层到表层的投射模式；（2）从4C层到皮质深层的投射；以及（3）从其他皮质层到4C层的投射。4Cα层和4Cβ层在向纹状皮质表层的投射模式上有所不同。4Cβ层神经元的轴突穿过4B层而不发出侧支，并终止于4A层和3B层底部。相比之下，4Cα层神经元的轴突终止于4B层，在4A/3B区域的密度较低。从4Cβ层到4A层的投射特别密集，以斑片状分布在每个注射部位的正上方。从4Cβ层到3B层的投射似乎密度较低且分布更广；我们估计单个4Cβ轴突可能横向扩散超过400微米。此外，向4A层和3B层注射后4Cβ层中HRP标记细胞体的模式为4Cβ层内的细分提供了证据。这些注射总是在4Cβ层上部产生大量标记神经元，而下部含有少量位于注射部位中心正下方的标记神经元。4Cα层和4Cβ层也都向皮质深层发出密度较低的投射。4Cβ层主要投射到6层，而4Cα层向5A层和6层都贡献轴突终末。6层的神经元为4C层提供了大部分皮质内投射。这些神经元的轴突口径很细，具有精致的侧棘形态，与外侧膝状体轴突分支明显不同。5A层的神经元也投射到4C层，但这些神经元的投射似乎集中在4Cα层。这些结果证实或完善了许多从高尔基材料得出的关于纹状皮质内在连接的结论，并提出了先前工作未怀疑的新连接模式。
