Integration of chemosensory pathways in the Drosophila second-order olfactory centers
Integration of chemosensory pathways in the Drosophila second-order olfactory centers
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DOI：
10.1016/j.cub.2004.03.006
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发表时间：
2004-03-23
期刊：
影响因子：
9.2
通讯作者：
Ito, K
中科院分区：
文献类型：
--
作者：
Tanaka, NK;Awasaki, T;Ito, K
背景：对气味的行为反应需要高级嗅觉中枢的神经元整合不同化学感觉神经元检测到的信号。最近的研究揭示了二级嗅觉神经元从一级嗅觉中枢到二级嗅觉中枢的典型树枝状分布，但三级嗅觉神经元如何阅读这一气味映射尚不清楚。结果：以果蝇脑为模型系统，我们分析了二级和三级嗅觉神经元之间的连接模式。我们首先在两个次级中枢，蘑菇体(MB)和侧角(LH)中分离出三个共同的投影区。每个区域通过来自触角叶小球特定亚群的二级神经元接收汇聚的信息。在MB中，三级神经元将它们的树突延伸到这些区域的各种组合中，这种异质神经元群体的轴突会聚在MB的输出区。相反，左脑三阶神经元的树枝分布被限制在一个区域内。此外，黄体生成素的不同区域与不同的脑区相连，并在触角叶小球的不同亚群和高级脑区之间形成优先联系。结论：MB是嗅觉学习和记忆不可或缺的部位，而黄体生成素的功能被报道足以介导对气味的直接非联想反应。二阶和三阶神经元的结构组织表明，MB能够跨肾小球整合广泛的气味信息，而嗅觉信号谱系的不同子集之间的整合可能在LH发生得相对较少。
Background: Behavioral responses to odorants require neurons of the higher olfactory centers to integrate signals detected by different chemosensory neurons. Recent studies revealed stereotypic arborizations of second-order olfactory neurons from the primary olfactory center to the secondary centers, but how third-order neurons read this odor map remained unknown.Results: Using the Drosophila brain as a model system, we analyzed the connectivity patterns between second-order and third-order olfactory neurons. We first isolated three common projection zones in the two secondary centers, the mushroom body (MB) and the lateral horn (LH). Each zone receives converged information via second-order neurons from particular subgroups of antennal-lobe glomeruli. In the MB, third-order neurons extend their dendrites across various combinations of these zones, and axons of this heterogeneous population of neurons converge in the output region of the MB. In contrast, arborizations of the third-order neurons in the LH are constrained within a zone. Moreover, different zones of the LH are linked with different brain areas and form preferential associations between distinct subsets of antennal-lobe glomeruli and higher brain regions.Conclusions: MB is known to be an indispensable site for olfactory learning and memory, whereas LH function is reported to be sufficient for mediating direct nonassociative responses to odors. The structural organization of second-order and third-order neurons suggests that MB is capable of integrating a wide range of odorant information across glomeruli, whereas relatively little integration between different subsets of the olfactory signal repertoire is likely to occur in the LH.