Seizure-induced neurogenesis in the adult brain.

It is well established that seizures increase adult neurogenesis in the subventricular and subgranular zones, the most neurogenic regions of the adult rodent and apparently human brain. However, the role of increased neurogenesis in these areas in seizure generation (ictogenesis) and epileptogenesis remains elusive. It is of utmost importance to explore how the cells that are born in response to epileptic seizures are functionally integrated into the existing neuronal networks, and how this integration would contribute to the excitability of this network. This will determine whether increased neurogenesis is beneficial or counteractive to ictogenesis and epileptogenesis. Some of the crucial factors affecting the functional integration of newborn cells seem to be excessive neuronal activity and/or inflammatory microenvironment, both associated with acute, as well as chronic, epileptic conditions. This review will focus on aspects of the functional integration of newborn cells in animal models of epilepsy with various degrees of seizure severity and associated microenvironmental alterations in the brain tissue.