27 - Slow Waves Associated with Seizure Activity

Abstract

The occurrence of specific patterns of electrical activity can characterize different types of brain activity and, in epilepsy, may indicate different mechanisms triggering seizure activity. Understanding mechanisms responsible for generation of these patterns could lead to new approaches in treatment to prevent seizure occurrence. This chapter presents an analysis of slow waves with durations of one second or more associated with different stages of seizures. These slow waves are a part of a complex pattern of brain electrical activity and other patterns of fast brain oscillations, such as theta, beta and gamma, ripples and fast ripples are superimposed on these slow waves. The chapter proposes that seizure associated slow waves reflect three processes—initiation of seizures, accumulation of extracellular potassium and changes in the pH of the extracellular space as a result of extensive neuronal discharges, and occurrence and propagation of spreading depression when concentration of extracellular potassium reaches a certain critical level. It is proposed that during each of these phases the mechanisms underlying the generation of slow waves are different and these mechanisms of slow wave generation may have distinct functional roles that contribute to seizure activity.