Unité de Neurosciences, Infomation et Complexité, Centre National de la Recherche Scientifique Gif-sur-Yvette, France.
Front Cell Neurosci. 2010 Mar 31;4:9. doi: 10.3389/fncel.2010.00009. eCollection 2010.
Cortical neurons in vivo may operate in high-conductance states, in which the major part of the neuron's input conductance is due to synaptic activity, sometimes several-fold larger than the resting conductance. We examine here the contribution of inhibition in such high-conductance states. At the level of the absolute conductance values, several studies have shown that cortical neurons in vivo are characterized by strong inhibitory conductances. However, conductances are balanced and spiking activity is mostly determined by fluctuations, but not much is known about excitatory and inhibitory contributions to these fluctuations. Models and dynamic-clamp experiments show that, during high-conductance states, spikes are mainly determined by fluctuations of inhibition, or by inhibitory "noise". This stands in contrast to low-conductance states, in which excitatory conductances determine spiking activity. To determine these contributions from experimental data, maximum likelihood methods can be designed and applied to intracellular recordings in vivo. Such methods indicate that action potentials are indeed mostly correlated with inhibitory fluctuations in awake animals. These results argue for a determinant role for inhibitory fluctuations in evoking spikes, and do not support feed-forward modes of processing, for which opposite patterns are predicted.
在体皮质神经元可能处于高电导状态，此时神经元的大部分输入电导是由突触活动引起的，有时比静息电导大几倍。我们在这里研究在这种高电导状态下抑制的作用。在绝对电导值的水平上，有几项研究表明，在体皮质神经元的特征是具有很强的抑制性电导。然而，电导是平衡的，并且尖峰活动主要由波动决定，但对于这些波动的兴奋和抑制贡献知之甚少。模型和动态钳位实验表明，在高电导状态下，尖峰主要由抑制的波动或抑制性“噪声”决定。这与低电导状态形成对比，在低电导状态下，兴奋电导决定了尖峰活动。为了从实验数据中确定这些贡献，可以设计并应用最大似然方法对在体细胞内记录进行分析。这些方法表明，在清醒动物中，动作电位确实主要与抑制性波动相关。这些结果表明抑制性波动在引发尖峰方面起着决定性的作用，不支持相反模式预测的前馈处理模式。
