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来自加州大学圣迭戈分校的Massimo Scanziani所带领的研究团队发现了大脑维持内部平衡的一个基础机制。他们通过对视觉皮层锥体细胞中的兴奋、抑制分析发现,二者之间的平衡关系(即E/I比平衡)同时存在于时间和空间两个层面上。这一机制的发现将有助于解释与大脑保持理想E/I比能力有关的神经疾病和神经退行性疾病。

                                                                                                                                                                          -2014年6月22日《自然》

中文翻译


【题目】视觉皮层神经元间的兴奋—抑制平衡

【译文】 哺乳动物大脑皮层中两种相反的作用力,突触兴奋和突触抑制之间的关系(可用E/I比表示)影响着许多大脑皮层功能如特征性选择和增益。尽管皮层活跃水平处于波动状态,个体的锥体形细胞在时间维度上仍表现出稳定的E/I比。这是因为当突触兴奋增加时,突触抑制也会通过募集抑制性神经元成比例地增加,这是一种被称为兴奋—抑制平衡的现象。然而,锥体形细胞上E/I比的分布情况还鲜为人知。通过自身高度相异的轴突,抑制性神经元可不加选择的与最邻近的锥体形细胞联络。那么抑制性物质是均一分配的,还是针对特异的锥体形细胞所接受兴奋不同的量单独匹配的呢?本研究中,我们发现了在小鼠初级视皮层的2/3层上,每一个锥体形细胞都接收到相同比例的兴奋和抑制。这导致了锥体形细胞间E/I比的平衡。这种匹配性的抑制是由表达小清蛋白而非表达生长激素抑制素的抑制性细胞所调控,并且由以不同锥体形细胞为靶标的个别表达小清蛋白的细胞发源出的突触进行独立调节所导致。此外,这种匹配是依赖于活跃程度的,因为它会随锥体形细胞活跃程度的打乱而陷入混乱。因此,锥体形细胞间的E/I比平衡揭示了一种意料之外的突触活力在空间分布上的有序度,并暗示着皮层两种相反力量之间的平衡不仅存在与时间维度上,还存在于空间维度上。

英文原稿


[Title]: Equalizing excitation–inhibition ratios across visual cortical neurons

[Authors]:  Mingshan Xue, Bassam V. Atallah, Massimo Scanziani

[Abstract]: The relationship between synaptic excitation and inhibition (E/I ratio), two opposing forces in the mammalian cerebral cortex, affects many cortical functions such as feature selectivity and gain. Individual pyramidal cells show stable E/I ratios in time despite fluctuating cortical activity levels. This is because when excitation increases, inhibition increases proportionally through the increased recruitment of inhibitory neurons, a phenomenon referred to as excitation–inhibition balance. However, little is known about the distribution of E/I ratios across pyramidal cells. Through their highly divergent axons, inhibitory neurons indiscriminately contact most neighbouring pyramidal cells. Is inhibition homogeneously distributed or is it individually matched to the different amounts of excitation received by distinct pyramidal cells? Here we discover that pyramidal cells in layer 2/3 of mouse primary visual cortex each receive inhibition in a similar proportion to their excitation. As a consequence, E/I ratios are equalized across pyramidal cells. This matched inhibition is mediated by parvalbumin-expressing but not somatostatin-expressing inhibitory cells and results from the independent adjustment of synapses originating from individual parvalbumin-expressing cells targeting different pyramidal cells. Furthermore, this match is activity-dependent as it is disrupted by perturbing pyramidal cell activity. Thus, the equalization of E/I ratios acrosspyramidal cells reveals an unexpected degree of order in the spatial distribution of synaptic strengths and indicates that the relationship between the cortex’s two opposing forces is stabilized not only in time but also in space.

原文地址:

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13321.html

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本文链接: http://www.bioku.cn/201406/nature-2014-6-22-equalizing-excitation-inhibition-ratios-across-visual-cortical-neurons/
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