Limbic Network Synchronization and Temporal Lobe Epilepsy

Excerpt

The limbic system generates synchronized physiological rhythms in the normal brain, notably in the theta rhythm, but also in the faster beta and gamma oscillations and sharp-wave ripples. In the epileptic brain synchronization becomes pathological thus generating seizures and several kinds of interictal activity as well as fast ripples (>250 Hz). Here, we outline the contributions made to seizure initiation, synchronization and termination by: (i) glutamatergic and GABAergic (including depolarizing GABAergic) synaptic transmission, (ii) non-synaptic mechanisms including ephaptic interactions, gap junctions and extracellular ions (particularly potassium), and (iii) glial homeostasis and transmission. We also consider the specific roles played by various components of the limbic circuit in seizure generation; for instance the ability of the hippocampal CA3 area to control seizure occurrence in others (such as entorhinal cortex) by generating interictal discharges. Finally we discuss whether targeting synchrony by electrical stimulation may be a potential therapeutic target.