Laboratory of Neural Microcircuitry, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
PLoS Biol. 2010 Sep 7;8(9):e1000473. doi: 10.1371/journal.pbio.1000473.
Inhibitory pathways are an essential component in the function of the neocortical microcircuitry. Despite the relatively small fraction of inhibitory neurons in the neocortex, these neurons are strongly activated due to their high connectivity rate and the intricate manner in which they interconnect with pyramidal cells (PCs). One prominent pathway is the frequency-dependent disynaptic inhibition (FDDI) formed between layer 5 PCs and mediated by Martinotti cells (MCs). Here, we show that simultaneous short bursts in four PCs are sufficient to exert FDDI in all neighboring PCs within the dimensions of a cortical column. This powerful inhibition is mediated by few interneurons, leading to strongly correlated membrane fluctuations and synchronous spiking between PCs simultaneously receiving FDDI. Somatic integration of such inhibition is independent and electrically isolated from monosynaptic excitation formed between the same PCs. FDDI is strongly shaped by I(h) in PC dendrites, which determines the effective integration time window for inhibitory and excitatory inputs. We propose a key disynaptic mechanism by which brief bursts generated by a few PCs can synchronize the activity in the pyramidal network.
抑制性通路是新皮层微电路功能的重要组成部分。尽管新皮层中的抑制性神经元比例相对较小，但由于其高连接率以及与锥体神经元（PC）相互连接的错综复杂方式，这些神经元被强烈激活。一个突出的途径是由 Martinotti 细胞（MC）介导的、层 5 PC 之间形成的频率依赖性双突触抑制（FDDI）。在这里，我们表明，四个 PC 中的同时短爆发足以在皮层柱维度内的所有相邻 PC 中发挥 FDDI。这种强大的抑制作用由少数中间神经元介导，导致同时接收 FDDI 的 PC 之间的膜波动和同步尖峰具有强烈相关性。这种抑制作用的躯体整合是独立的，与同一 PC 之间形成的单突触兴奋是电隔离的。FDDI 在 PC 树突中的 I(h) 中受到强烈影响，这决定了抑制性和兴奋性输入的有效整合时间窗口。我们提出了一个关键的双突触机制，即由少数几个 PC 产生的短暂爆发可以使锥体网络的活动同步。
