Piwkowska Zuzanna, Pospischil Martin, Brette Romain, Sliwa Julia, Rudolph-Lilith Michelle, Bal Thierry, Destexhe Alain
Unité de Neurosciences Intégratives et Computationnelles , CNRS, 91198 Gif-sur-Yvette, France.
J Neurosci Methods. 2008 Apr 30;169(2):302-22. doi: 10.1016/j.jneumeth.2007.11.010. Epub 2007 Nov 22.
Cortical neurons are subject to sustained and irregular synaptic activity which causes important fluctuations of the membrane potential (V(m)). We review here different methods to characterize this activity and its impact on spike generation. The simplified, fluctuating point-conductance model of synaptic activity provides the starting point of a variety of methods for the analysis of intracellular V(m) recordings. In this model, the synaptic excitatory and inhibitory conductances are described by Gaussian-distributed stochastic variables, or "colored conductance noise". The matching of experimentally recorded V(m) distributions to an invertible theoretical expression derived from the model allows the extraction of parameters characterizing the synaptic conductance distributions. This analysis can be complemented by the matching of experimental V(m) power spectral densities (PSDs) to a theoretical template, even though the unexpected scaling properties of experimental PSDs limit the precision of this latter approach. Building on this stochastic characterization of synaptic activity, we also propose methods to qualitatively and quantitatively evaluate spike-triggered averages of synaptic time-courses preceding spikes. This analysis points to an essential role for synaptic conductance variance in determining spike times. The presented methods are evaluated using controlled conductance injection in cortical neurons in vitro with the dynamic-clamp technique. We review their applications to the analysis of in vivo intracellular recordings in cat association cortex, which suggest a predominant role for inhibition in determining both sub- and supra-threshold dynamics of cortical neurons embedded in active networks.
皮层神经元会受到持续且不规则的突触活动影响，这种活动会导致膜电位（V(m)）出现重要波动。我们在此回顾表征这种活动及其对动作电位产生影响的不同方法。简化的、波动的突触活动点电导模型为分析细胞内V(m)记录提供了多种方法的起点。在该模型中，突触兴奋性和抑制性电导由高斯分布的随机变量描述，即“有色电导噪声”。将实验记录的V(m)分布与从该模型导出的可逆理论表达式进行匹配，能够提取表征突触电导分布的参数。这种分析可以通过将实验V(m)功率谱密度（PSD）与理论模板进行匹配来补充，尽管实验PSD出人意料的标度特性限制了后一种方法的精度。基于这种对突触活动的随机表征，我们还提出了定性和定量评估动作电位之前突触时间进程的动作电位触发平均值的方法。该分析指出突触电导方差在确定动作电位时间方面起着重要作用。使用动态钳技术在体外皮层神经元中进行受控电导注入来评估所提出的方法。我们回顾它们在分析猫联合皮层体内细胞内记录中的应用，这表明抑制在确定嵌入活跃网络中的皮层神经元的阈下和阈上动态方面起主要作用。
