Institute of Neuroinformatics, UZH/ETH, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
Brain Struct Funct. 2017 Sep;222(7):3025-3042. doi: 10.1007/s00429-017-1384-4. Epub 2017 Feb 27.
The present study is the first to describe quantitatively the patterns of synaptic connections made by the patchy network of pyramidal cell axons in the superficial layers of cat V1 in relation to the orientation map. Intrinsic signal imaging of the orientation map was combined with 3D morphological reconstructions of physiologically-characterized neurons at light and electron microscope levels. A Similarity Index (SI) expressed the similarity of the orientation domain of a given bouton cluster to that of its parent dendritic tree. Six pyramidal cells whose axons had a wide range of SIs were examined. Boutons were sampled from five local and five distal clusters, and from the linear segments that link the clusters. The synaptic targets were reconstructed by serial section electron microscopy. Of the 233 synapses examined, 182 synapses were formed with spiny neurons, the remainder with smooth neurons. The proportion of smooth neurons that were synaptic targets varied greatly (from 0 to 50%) between the cluster samples, but was not correlated with the SI. The postsynaptic density sizes were similar for synapses in local and distal clusters, regardless of their SI. This heterogeneity in the synaptic targets of single cells within the superficial layers is a network feature well-suited for context-dependent processing.
本研究首次定量描述了猫视皮层 V1 浅层中由片状锥体细胞轴突网络形成的突触连接模式与方位图之间的关系。方位图的内源性信号成像与光镜和电镜水平上对生理特性神经元的 3D 形态重建相结合。相似性指数（SI）表示给定一簇突触点的方位域与其母树突的相似程度。对 6 个具有广泛 SI 的锥体细胞进行了检查。从五个局部簇和五个远端簇以及连接簇的线性段中取样突触点。通过连续切片电子显微镜重建了突触后靶标。在检查的 233 个突触中，182 个形成于棘突神经元，其余形成于光滑神经元。在簇样本之间，作为突触后靶标的光滑神经元的比例变化很大（从 0 到 50%），但与 SI 无关。局部和远端簇中无论其 SI 如何，突触后密度大小都相似。这种浅层中单细胞的突触后靶标异质性是一种非常适合上下文相关处理的网络特征。
