Rudolph Michael, Pelletier Joe Guillaume, Paré Denis, Destexhe Alain
Unité de Neuroscience Intégratives et Computationnelles, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
J Neurophysiol. 2005 Oct;94(4):2805-21. doi: 10.1152/jn.01313.2004. Epub 2005 Jul 13.
The activation of the electroencephalogram (EEG) is paralleled with an increase in the firing rate of cortical neurons, but little is known concerning the conductance state of their membrane and its impact on their integrative properties. Here, we combined in vivo intracellular recordings with computational models to investigate EEG-activated states induced by stimulation of the brain stem ascending arousal system. Electrical stimulation of the pedonculopontine tegmental (PPT) nucleus produced long-lasting (approximately 20 s) periods of desynchronized EEG activity similar to the EEG of awake animals. Intracellularly, PPT stimulation locked the membrane into a depolarized state, similar to the up-states seen during deep anesthesia. During these EEG-activated states, however, the input resistance was higher than that during up-states. Conductance measurements were performed using different methods, which all indicate that EEG-activated states were associated with a synaptic activity dominated by inhibitory conductances. These results were confirmed by computational models of reconstructed pyramidal neurons constrained by the corresponding intracellular recordings. These models indicate that, during EEG-activated states, neocortical neurons are in a high-conductance state consistent with a stochastic integrative mode. The amplitude and timing of somatic excitatory postsynaptic potentials were nearly independent of the position of the synapses in dendrites, suggesting that EEG-activated states are compatible with coding paradigms involving the precise timing of synaptic events.
脑电图（EEG）的激活与皮质神经元放电率的增加同时出现，但关于其细胞膜的电导状态及其对整合特性的影响却知之甚少。在这里，我们将体内细胞内记录与计算模型相结合，以研究脑干上行唤醒系统刺激所诱导的EEG激活状态。对脚桥被盖核（PPT）进行电刺激会产生类似于清醒动物脑电图的持久（约20秒）去同步化脑电图活动。在细胞内，PPT刺激会使膜锁定在去极化状态，类似于深度麻醉期间出现的上行状态。然而，在这些EEG激活状态下，输入电阻高于上行状态期间。使用不同方法进行了电导测量，所有测量结果均表明EEG激活状态与以抑制性电导为主导的突触活动相关。这些结果通过受相应细胞内记录约束的重建锥体神经元计算模型得到了证实。这些模型表明，在EEG激活状态下，新皮质神经元处于与随机整合模式一致的高电导状态。体细胞兴奋性突触后电位的幅度和时间几乎与突触在树突中的位置无关，这表明EEG激活状态与涉及突触事件精确时间的编码范式兼容。
