Sensory maps in the olfactory cortex defined by long-range viral tracing of single neurons

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. Activation of each glomerulus is relayed to higher cortical processing centres by a set of ～20-50 'homotypic' mitral and tufted (MT) neurons. In the cortex, target neurons integrate information from multiple glomeruli to detect distinct features of chemically diverse odours. 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.     

加快推进民族地区城乡公共服务一体化

由于城乡和区域发展不平衡所造成的深层次矛盾突出,民族地区在公共服务领域和其他地区还存在明显的差距。加快推进民族地区城乡公共服务一体化进程,其基本途径是统筹城乡发展,在加快转变经济发展方式中促进城乡一体化,以保障和改善民生为重点,以完善的制度安排和政策体系为保障,加大中央财政在教育、医疗卫生、社会保障、公共基础设施等方面对民族地区的扶持力度,创新社会管理,逐步形成覆盖城乡居民的基本公共服务体系。