Sensory maps in the olfactory cortex defined by long-range viral tracing of single neurons
Sensory maps in the olfactory cortex defined by long-range viral tracing of single neurons
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DOI：
10.1038/nature09945
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发表时间：
2011-04-14
期刊：
影响因子：
64.8
通讯作者：
Baldwin, Kristin K.
中科院分区：
文献类型：
--
作者：
Ghosh, Sulagna;Larson, Stephen D.;Baldwin, Kristin K.
感觉信息在大脑中可能通过轴突输入的定型映射或个体间不同的模式来呈现。在嗅觉方面，在第一个感觉处理中心——嗅球（OB）中存在明显的定型图谱，不同的气味会以空间不变的肾小球的独特组合模式引发活动（1,2）。每个肾小球的激活由一组约20 - 50个“同型” mitral和tufted（MT）神经元传递到更高的皮质处理中心（3）。在皮质中，目标神经元整合来自多个肾小球的信息以检测化学性质多样的气味的不同特征（4 - 6）。这是如何实现的仍不清楚，也许是因为单个MT神经元对肾小球信息的皮质映射尚未被描述。在此，我们使用新的病毒追踪和三维大脑重建方法来比较特定组MT神经元的皮质投射。我们表明，嗅球的大体组织结构在到一个处理中心的轴突投射模式中得以保留，但在另一个处理中心则重新排列，这表明不同的编码策略可能在不同的目标中起作用。然而，在单个神经元层面，无论是肾小球顺序还是定型性在这两个区域都未被保留。相反，来自同一肾小球的同型MT神经元支配个体间不同的广泛区域。令人惊讶的是，即使在同一动物中，MT神经元在连接上也表现出广泛的多样性；同型MT对的轴突彼此分开，在不同位置发出初级分支，并且同型和异型对的70 - 90%的分支不重叠。皮质中感觉图谱的这种显著重组为来自空间上不同的肾小球的信息的扩展组合整合提供了解剖学基础，并预示了原本相似的输出神经元多样化的一种意想不到的作用。
Sensory information may be represented in the brain by stereotyped mapping of axonal inputs or by patterning that varies between individuals. In olfaction, a stereotyped map is evident in the first sensory processing centre, the olfactory bulb (OB), where different odours elicit activity in unique combinatorial patterns of spatially invariant glomeruli(1,2). Activation of each glomerulus is relayed to higher cortical processing centres by a set of similar to 20-50 'homotypic' mitral and tufted (MT) neurons(3). In the cortex, target neurons integrate information from multiple glomeruli to detect distinct features of chemically diverse odours(4-6). How this is accomplished remains unclear, perhaps because the cortical mapping of glomerular information by individual MT neurons has not been described. Here we use new viral tracing and three-dimensional brain reconstruction methods to compare the cortical projections of defined sets of MT neurons. We show that the gross-scale organization of the OB is preserved in the patterns of axonal projections to one processing centre yet reordered in another, suggesting that distinct coding strategies may operate in different targets. However, at the level of individual neurons neither glomerular order nor stereotypy is preserved in either region. Rather, homotypic MT neurons from the same glomerulus innervate broad regions that differ between individuals. Strikingly, even in the same animal, MT neurons exhibit extensive diversity in wiring; axons of homotypic MT pairs diverge from each other, emit primary branches at distinct locations and 70-90% of branches of homotypic and heterotypic pairs are non-overlapping. This pronounced reorganization of sensory maps in the cortex offers an anatomic substrate for expanded combinatorial integration of information from spatially distinct glomeruli and predicts an unanticipated role for diversification of otherwise similar output neurons.