Morpho-functional study of converging axonal projections in the auditory cortex

一小群皮质神经元投射局部的短距离轴突。这种突起在皮质区域不是弥漫性或均匀分布的，而是在距离注射部位数百μm处形成终末轴突斑块，以及注射部位周围的密集轴突丛。来自不同皮层位置的末端轴突的片状组织是如何相互作用的，但代表不同的感觉特征？一个特定的皮质部位只从一个皮质部位还是从多个其他皮质部位接收信息？在后一种情况下，必须有某种信息的汇合。揭示大脑皮层的会聚模式对于理解大脑皮层的某些基本机制至关重要。在麻醉状态下，用对侧耳纯音刺激，用常规电生理方法对猫的听觉核心区进行了定位。然后两种示踪剂，菜豆白细胞凝集素 ...更多信息 将生物素化的葡聚糖胺（BDA）和替宁（PHA-L）离子导入近距离，在约500至1000 μm处分离。注射部位覆盖直径约300-500 μm的皮质区域。从听觉皮层切下切向切片后，PHA-L和BDA分别对不同的颜色进行反应;紫色到黑色和棕色。不同标记的轴突起源于不同的示踪剂注射部位进行了扫描，其分布在听觉皮层。鉴定仅含有两个示踪剂标记的轴突之一的区域和含有两个示踪剂标记的轴突的区域。注射到初级听觉皮层（Al）的中心部分导致标记轴突的斑块分布在注射部位的内侧和外侧，而注射到更靠后的部分导致斑块分布更广泛，除了注射部位的内侧和后部之外，还包括前部和后部。在这两种注射情况下，重叠分布的PHA-L标记的轴突和BDA标记的轴突主要是在最远的补丁内侧和外侧。由于在猫A1上形成了一个系统的频率音调拓扑图，结果表明与高频和低频加工有关的局部回路采取不同的连接形式。少

A small population of cortical neurons project local, short-distance axons. This projection is not diffusely or homogeneously distributed over the cortical region, but forms patches of terminal axons at several hundred μm distant from injection site, in addition to a dense plexus of axons around injection site. How do patchy organizations of terminal axons originating from different cortical sites located closely but representing different sensory features interact each other? Does a particular cortical site receive information only from one cortical site or from multiple other cortical sites? In the latter case, there must take place some convergence of information. Revealing the pattern of cortical convergence seems to be crucial to understanding some basic mechanism of cerebral cortex.Under aneasthetic condition, the auditory corex of cats were mapped using the conventional electrophysiology by applying pure tones to contralateral ear. Then two tracers, phaseolus vulgaris leukoagglu … More tinin (PHA-L) and biotinylated dextran amine (BDA), were ionotophoretically injected in close proximity, separating at about 500 to 1000 μm. Injection sites covered cortical area of about 300-500 μm in diameter. After cutting tangential sections from the auditory cortex, PHA-L and BDA were reacted for different colors ; purple to black and brown, respectively. Differentially labeled axons originating from different tracer injection sites were scanned for their distribution over the auditory cortex. Areas which contain only one of the two tracer-labeled axons and areas which contain both tracer-labeled axons were identified. Injections into the center part of the primary auditory cortex (Al) resulted in patches of labeled axon distributing medial and lateral to the injection site, while injections into more posteriorly located part resulted in patches distributing more widely, including anterior and posterior in addition to medial and posterior to injection site. In both injection cases, overlapping distribution of PHA-L-labeled axons and BDA-labeled axons was found mainly at the most distal patches medially and laterally. Since a systematic tonotopic map of frequency is formed across cat Al, the results indicate that local circuits related to high-frequency and low-frequency processing take different form of connection. Less