The ability of the olfactory system to detect and discriminate a broad spectrum of odor molecules with extraordinary sensitivity relies on a wide range of odorant receptors and on the distinct architecture of neuronal circuits in olfactory brain areas. More than 1000 odorant receptors, distributed almost randomly in the olfactory epithelium, are plotted out in two mirror-symmetric maps of glomeruli in the olfactory bulb, the first relay station of the olfactory system. How does such a precise spatial arrangement of glomeruli emerge from a random distribution of receptor neurons? Remarkably, the identity of odorant receptors defines not only the molecular receptive range of sensory neurons but also their glomerular target. Despite their key role, odorant receptors are not the only determinant, since the specificity of neuronal connections emerges from a complex interplay between several molecular cues and electrical activity. This review provides an overview of the mechanisms underlying olfactory circuit formation. In particular, recent findings on the role of odorant receptors in regulating axon targeting and of spontaneous activity in the development and maintenance of synaptic connections are discussed.

中文翻译：

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嗅球中的地形组织

嗅觉系统以极高的灵敏度检测和区分广谱气味分子的能力依赖于广泛的气味受体和嗅觉大脑区域神经元回路的独特结构。超过 1000 个气味受体几乎随机分布在嗅觉上皮细胞中，它们被绘制在嗅球中肾小球的两个镜像对称图中，嗅球是嗅觉系统的第一个中继站。如此精确的肾小球空间排列是如何从随机分布的受体神经元中产生的？值得注意的是，气味受体的身份不仅定义了感觉神经元的分子接收范围，还定义了它们的肾小球靶标。尽管它们起着关键作用，但气味受体并不是唯一的决定因素，因为神经元连接的特异性来自几个分子线索和电活动之间复杂的相互作用。本综述概述了嗅觉回路形成的潜在机制。特别是，讨论了最近关于气味受体在调节轴突靶向和自发活动在突触连接的发展和维持中的作用的发现。