Neuronal networks, epilepsy, and other brain dysfunctions

AbstractThe dynamics of highly interconnected networks of neurones are fundamental to both normal and pathological functioning of the brain. Epilepsy is perhaps the most dramatic example of a dysfunctional neuronal network, characterized by intense and highly synchronous neuronal activity, but more subtle dysfunction is associated with other conditions, such as schizophrenia. This chapter will largely focus on the hippocampus, and to a lesser degree on the neocortex. The hippocampal formation is implicated in several important psychiatric and neurological problems. The hippocampus and amygdala are often the site of epileptic foci, which can lead to problems in learning and memory, emotion, anxiety, and other problems. This kind of epilepsy is variously known as temporal lobe epilepsy, complex partial seizures, or limbic epilepsy. The hippocampus and associated limbic areas have been linked both to affective disorders and to psychoses. This chapter will consider the cellular organization of the hippocampus and then outline aspects of the emergent properties of neuronal networks in the hippocampus and speculative role in psychiatric disorders. Cellular and network mechanisms of focal epilepsy, and learning impairments associated with limbic epilepsy will be reviewed.