25 - A Neuronal Network Model of Corticothalamic Oscillations: The Emergence of Epileptiform Absence Seizures

Abstract

Absence seizures are paroxysmal losses of consciousness of abrupt onset and offset, accompanied by bilaterally synchronous spike-and-wave (SW) discharges in the EEG. It is currently considered that the mechanisms underlying SW discharges may be related to the thalamocortical mechanisms of sleep spindle generation. The cellular mechanisms for the generation of spindle oscillations during sleep appear to be related to those for the generation of the spike-and-wave (SW) complexes that are associated with absence (petit mal) epileptic seizures. Despite the fact that cellular and network mechanisms underlying spindle and SW rhythmicity are clarified to a large extent, the mechanisms that are responsible for the spontaneous transition between normal spindle and paroxysmal SW oscillations are not well understood. This chapter approaches the given problem at the intermediate level between the microscopic and macroscopic levels. That is, the explicit behavior of individual neurons is not stimulated but rather model the populations of interacting neurons integrating neuronal and network properties. The rationale for such a modeling level is to take advantage of the lumped modeling approach but, at the same time, to include some essential processes at the level of neurons' membrane that are responsible for burst generation in thalamic cells.