Functional transitions between epileptiform-like activity and associative memory in hippocampal region CA3.

Clinical and experimental observations indicate that the hippocampus is critical in the formation of declarative memories. Interestingly, electrophysiological studies have demonstrated that the region also has a particularly low seizure threshold, where globally synchronous synaptic activity can occur. By using a detailed biophysical model of area CA3, it is shown how septal cholinergic modulation, through three distinct mechanisms, can interact with intrinsic and synaptic conductances to influence population behavior. A dissection of each mechanism demonstrates a variety of population firing activity ranging from fully synchronized behavior to a mixture of repetitive bursting and oscillations in reduced subsets of neurons, ideal for forming accurate associations during a learning and recall task.