Hof P R, Ungerleider L G, Webster M J, Gattass R, Adams M M, Sailstad C A, Morrison J H
Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
J Comp Neurol. 1996 Dec 2;376(1):112-27. doi: 10.1002/(SICI)1096-9861(19961202)376:1<112::AID-CNE7>3.0.CO;2-6.
Previous studies of the primate cerebral cortex have shown that neurofilament protein is present in pyramidal neuron subpopulations displaying specific regional and laminar distribution patterns. In order to characterize further the neurochemical phenotype of the neurons furnishing feedforward and feedback pathways in the visual cortex of the macaque monkey, we performed an analysis of the distribution of neurofilament protein in corticocortical projection neurons in areas V1, V2, V3, V3A, V4, and MT. Injections of the retrogradely transported dyes Fast Blue and Diamidino Yellow were placed within areas V4 and MT, or in areas V1 and V2, in 14 adult rhesus monkeys, and the brains of these animals were processed for immunohistochemistry with an antibody to nonphosphorylated epitopes of the medium and heavy molecular weight subunits of the neurofilament protein. Overall, there was a higher proportion of neurons projecting from areas V1, V2, V3, and V3A to area MT that were neurofilament protein-immunoreactive (57-100%), than to area V4 (25-36%). In contrast, feedback projections from areas MT, V4, and V3 exhibited a more consistent proportion of neurofilament protein-containing neurons (70-80%), regardless of their target areas (V1 or V2). In addition, the vast majority of feedback neurons projecting to areas V1 and V2 were located in layers V and VI in areas V4 and MT, while they were observed in both supragranular and infragranular layers in area V3. The laminar distribution of feedforward projecting neurons was heterogeneous. In area V1, Meynert and layer IVB cells were found to project to area MT, while neurons projecting to area V4 were particularly dense in layer III within the foveal representation. In area V2, almost all neurons projecting to areas MT or V4 were located in layer III, whereas they were found in both layers II-III and V-VI in areas V3 and V3A. These results suggest that neurofilament protein identifies particular subpopulations of corticocortically projecting neurons with distinct regional and laminar distribution in the monkey visual system. It is possible that the preferential distribution of neurofilament protein within feedforward connections to area MT and all feedback projections is related to other distinctive properties of these corticocortical projection neurons.
以往对灵长类动物大脑皮层的研究表明，神经丝蛋白存在于具有特定区域和层状分布模式的锥体神经元亚群中。为了进一步表征猕猴视觉皮层中提供前馈和反馈通路的神经元的神经化学表型，我们分析了V1、V2、V3、V3A、V4和MT区皮质-皮质投射神经元中神经丝蛋白的分布。在14只成年恒河猴中，将逆行运输染料快蓝和双脒基黄注射到V4和MT区，或V1和V2区，然后用针对神经丝蛋白中、重分子量亚基非磷酸化表位的抗体对这些动物的大脑进行免疫组织化学处理。总体而言，从V1、V2、V3和V3A区投射到MT区的神经丝蛋白免疫反应性神经元比例较高（57%-100%）, 高于投射到V4区的比例（25%-36%）。相比之下，来自MT、V4和V3区的反馈投射显示，无论其靶区是V1还是V2，含神经丝蛋白的神经元比例更为一致（70%-80%）。此外，绝大多数投射到V1和V2区的反馈神经元位于V4和MT区的V层和VI层，而在V3区的颗粒上层和颗粒下层均有发现。前馈投射神经元的层状分布是不均匀的。在V1区，发现迈内特细胞和IVB层细胞投射到MT区，而投射到V4区的神经元在中央凹代表区的III层特别密集。在V2区，几乎所有投射到MT区或V4区的神经元都位于III层，而在V3和V3A区，它们则在II-III层和V-VI层均有发现。这些结果表明，神经丝蛋白可识别猕猴视觉系统中具有不同区域和层状分布的特定皮质-皮质投射神经元亚群。神经丝蛋白在前馈连接到MT区和所有反馈投射中的优先分布可能与这些皮质-皮质投射神经元的其他独特特性有关。
