Computational modeling of depth-EEG signals observed in interictal to ictal transition in human temporal lobe epilepsy

This paper focuses on high-frequency EEG activities (gamma band), a characteristic electrophysiological pattern observed during interictal to ictal transition in human epilepsy. Starting from recently published results about i) the behavior of inhibitory interneurons in hippocampal or neocortical networks in the generation of gamma frequency oscillations, ii) the nonuniform alteration of GABAergic inhibition in experimental epilepsy (reduced dendritic inhibition and increased somatic inhibition) and iii) the possible depression of GABA(A,fast) circuit activity by GABA(A,slow) inhibitory post-synaptic currents, this paper describes a new computational macroscopic model of EEG activity that includes a physiologically relevant fast inhibitory feedback loop. Results show that strikingly realistic activities are produced by the model when compared to real depth-EEG epileptic signals recorded with intracerebral electrodes. They show that the transition between interictal to fast ictal activity is explained, in the model, by the impairment of dendritic inhibition.