Dolorfo C L, Amaral D G
Group in Neuroscience, University of California at San Diego, La Jolla 92193, USA.
J Comp Neurol. 1998 Aug 17;398(1):25-48.
By using three-dimensional computer reconstruction techniques and the production of two-dimensional unfolded maps, we analyzed the topographic organization of projections from the entorhinal cortex of the rat to the dentate gyrus. The retrograde tracers, Fast blue and Diamidino yellow, were injected at all septotemporal levels of the dentate gyrus, and the distribution of retrogradely labeled layer II cells in the entorhinal cortex was plotted by using computer-aided microscopy systems. Discrete injections of fluorescent dyes into the dentate gyrus labeled bands of layer II neurons in the entorhinal cortex that covered approximately 45% of its surface area. Injections confined to the septal half of the dentate gyrus resulted in a band that occupied the most lateral and caudomedial portions of the entorhinal cortex. Although there were subtle changes in the density of labeled cells in this region, essentially the same region of cells was labeled after any injection into the septal half of the dentate gyrus. Injections into mid-septotemporal levels of the dentate gyrus (50-75% of the distance from the septal pole) led to a distinctly different pattern of retrograde labeling. A more medial portion of the lateral entorhinal cortex and a more rostral portion of the medial entorhinal area were labeled in these cases. Another change in entorhinal labeling occurred when the injection involved the most temporal quarter of the dentate gyrus. Injections into this area led to a constrained region of entorhinal labeling that included the most medial portion of the lateral entorhinal area and the most rostral portion of the medial entorhinal area. Although the domains of cells projecting to septal, mid-septotemporal, and temporal levels of the dentate gyrus were not entirely segregated, there was relatively little overlap of the three populations of neurons. These data raise the possibility that different portions of the entorhinal-hippocampal circuit are capable of semiautonomous information processing, at least at the stage of input to the dentate gyrus.
通过使用三维计算机重建技术和制作二维展开图，我们分析了大鼠内嗅皮质至齿状回投射的拓扑组织。将逆行示踪剂快蓝和双脒基黄注射到齿状回的所有前后水平，并用计算机辅助显微镜系统绘制内嗅皮质中逆行标记的II层细胞的分布。向齿状回离散注射荧光染料标记了内嗅皮质中II层神经元的条带，其覆盖了约45%的表面积。局限于齿状回隔区一半的注射产生了一条占据内嗅皮质最外侧和尾内侧部分的条带。尽管该区域标记细胞的密度有细微变化，但在向齿状回隔区一半进行任何注射后，基本上标记的是相同的细胞区域。向齿状回中隔颞水平（距隔极距离的50 - 75%）注射导致逆行标记模式明显不同。在这些情况下，外侧内嗅皮质的更内侧部分和内侧内嗅区的更靠前部分被标记。当注射涉及齿状回最颞侧四分之一时，内嗅标记发生了另一种变化。向该区域注射导致内嗅标记的局限区域，包括外侧内嗅区的最内侧部分和内侧内嗅区的最靠前部分。尽管投射到齿状回隔区、中隔颞区和颞区水平的细胞区域并非完全分离，但这三类神经元群体的重叠相对较少。这些数据增加了一种可能性，即内嗅 - 海马回路的不同部分能够进行半自主信息处理，至少在输入到齿状回的阶段是这样。
