The balance between excitatory and inhibitory (E and I) synapses is thought to be critical for information processing in neural circuits. However, little is known about the spatial principles of E and I synaptic organization across the entire dendritic tree of mammalian neurons. We developed a new open-source reconstruction platform for mapping the size and spatial distribution of E and I synapses received by individual genetically-labeled layer 2/3 (L2/3) cortical pyramidal neurons (PNs) in vivo. We mapped over 90,000 E and I synapses across twelve L2/3 PNs and uncovered structured organization of E and I synapses across dendritic domains as well as within individual dendritic segments. Despite significant domain-specific variation in the absolute density of E and I synapses, their ratio is strikingly balanced locally across dendritic segments. Computational modeling indicates that this spatially precise E/I balance dampens dendritic voltage fluctuations and strongly impacts neuronal firing output.

中文翻译：

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全神经元突触定位揭示了空间精确的兴奋性/抑制性平衡，限制了树突状和体细胞突增。

兴奋性和抑制性（E和I）突触之间的平衡被认为对于神经回路中的信息处理至关重要。然而，关于哺乳动物神经元整个树突树中E和I突触组织的空间原理知之甚少。我们开发了一个新的开源重建平台，用于绘制个体遗传标记的第2/3层（L2 / 3）皮质锥体神经元（PNs）在体内接收到的E和I突触的大小和空间分布。我们在12个L2 / 3 PN上绘制了超过90,000个E和I突触，并在树突域以及单个树突节内未发现E和I突触的结构化组织。尽管E和I突触的绝对密度存在明显的域特定变化，但它们的比率在整个树突节段中均达到局部显着平衡。