Plasticity-driven individualization of olfactory coding in mushroom body output neurons.
Plasticity-driven individualization of olfactory coding in mushroom body output neurons.
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DOI：
10.1038/nature15396
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发表时间：
2015-10-08
期刊：
影响因子：
64.8
通讯作者：
Turner GC
中科院分区：
文献类型：
--
作者：
Hige T;Aso Y;Rubin GM;Turner GC
尽管所有的感觉回路都上升到更高的大脑区域，在那里刺激以稀疏的、刺激特定的活动模式表现出来，但相对而言，人们对神经回路下降端的感觉编码知之甚少，因为网络是收敛的。在昆虫中，蘑菇体一直是研究嗅觉系统稀疏编码的重要模型系统，这种格式对准确的记忆形成很重要。在果蝇中，最近的研究表明，MB的2000个凯尼恩细胞（KCs）汇聚到一个只有35个MB输出神经元（MBONs）的群体中，这些神经元在解剖学上分为22种不同的细胞类型。在这里，我们提供了嗅觉表征的第一个全面的观点，在电路的第四层，我们发现一个明显的转变在感觉编码的原则。我们发现MBON调谐曲线彼此之间高度相关。这与电路的早期层中逐步去相关调谐的过程形成鲜明对比。相反，在人口水平上，气味表征被重新格式化，以便不同气味表征之间出现正相关和负相关。在单细胞水平上，我们发现，在不同的动物中，唯一可识别的mbon表现出截然不同的调谐，但在单个苍蝇的两个半球中，同一神经元的调谐几乎是相同的。因此，在嗅觉回路的这一层次上产生了个性化的调谐协调。此外，我们发现这种个性化是一个主动的过程，需要一个与学习相关的基因，芜菁。最终，神经回路必须灵活地将稀疏层中高度刺激特异性的信息映射到有限数量的不同运动输出上。我们在这里观察到的感觉表征的重新格式化可能标志着嗅觉系统中这种感觉-运动转换的开始。
Although all sensory circuits ascend to higher brain areas where stimuli are represented in sparse, stimulus-specific activity patterns, relatively little is known about sensory coding on the descending side of neural circuits, as a network converges. In insects, mushroom bodies (MBs) have been an important model system for studying sparse coding in the olfactory system, where this format is important for accurate memory formation. In Drosophila, it has recently been shown that the 2000 Kenyon cells (KCs) of the MB converge onto a population of only 35 MB output neurons (MBONs), that fall into 22 anatomically distinct cell types. Here we provide the first comprehensive view of olfactory representations at the fourth layer of the circuit, where we find a clear transition in the principles of sensory coding. We show that MBON tuning curves are highly correlated with one another. This is in sharp contrast to the process of progressive decorrelation of tuning in the earlier layers of the circuit. Instead, at the population level, odor representations are reformatted so that positive and negative correlations arise between representations of different odors. At the single-cell level, we show that uniquely identifiable MBONs display profoundly different tuning across different animals, but tuning of the same neuron across the two hemispheres of an individual fly was nearly identical. Thus, individualized coordination of tuning arises at this level of the olfactory circuit. Furthermore, we find that this individualization is an active process that requires a learning-related gene, rutabaga. Ultimately, neural circuits have to flexibly map highly stimulus-specific information in sparse layers onto a limited number of different motor outputs. The reformatting of sensory representations we observe here may mark the beginning of this sensory-motor transition in the olfactory system.