Epilepsy as a dynamic disease of neuronal networks

Epilepsy is a dynamic disease of neuronal networks. To understand how epileptic seizures occur, it is necessary to take into account that the brain of epileptic subjects is able to function in two very distinct modes: a normal state and a state characterized by abnormal oscillations, i.e., epileptic seizures. A main question is how the transition (i.e., a bifurcation) from the normal to the epileptic state can take place. Such transitions do not occur easily in the normal brain due to the set of parameters that maintains the stability of the neuronal networks. In the brain of epileptic subjects, however, these parameters are disturbed so that the threshold for these transitions is much lower and may occur spontaneously. This is the essential difference between the dynamics of a normal and an epileptic brain. Here we consider, first, the main aspects of how the stability of neuronal networks may be maintained and disturbed in epilepsy. Thereafter we discuss how transitions between normal and epileptic behavior may occur in two important systems with respect to epilepsy: networks of the thalamocortical and the hippocampal systems. Finally, the question of how neuronal networks involved in epileptic behavior may be identified in the clinic is analyzed