FUNCTIONAL TRANSITIONS BETWEEN EPILEPTIFORM-LIKE ACTIVITY AND ASSOCIATIVE MEMORY IN HIPPOCAMPAL REGION CA3

Clinical and experimental observations indicate that the hippocampus i s critical in the formation of declarative memories. Interestingly, el ectrophysiological studies have demonstrated that the region also has a particularly low seizure threshold, where globally synchronous synap tic activity can occur. By using a detailed biophysical model of area CA3, it is shown how septal cholinergic modulation, through three dist inct mechanisms, can interact with intrinsic and synaptic conductances to influence population behavior. A dissection of each mechanism demo nstrates a variety of population firing activity ranging from fully sy nchronized behavior to a mixture of repetitive bursting and oscillatio ns in reduced subsets of neurons, ideal for forming accurate associati ons during a learning and recall task. (C) 1997 Elsevier Science Inc.