Instability in a hippocampal neural network.

Four computer models, HM1-HM4, of a particular hippocampal neural network have been developed. The models represent two cell populations, the pyramidal cells and the basket cells; the populations are coupled so that pyramidal cells are inhibited by activity they excite in the basket cell population. In models HM2-HM4, this recurrent inhibitory pathway contains a temporal dispersion element. Models HM3-HM4 place the pyramidal cells in an additional recurrent excitatory feedback loop. HM4 represents a pair of interacting hippocampal networks. Simulated network responses to single-shock stimulation are presented for various parameter values of the four models. Calculations are extended more than one second following stimulation. Particular attention is given to simulation of network instabilities. Simulated neural activity is discussed in view of experimental work on normal (nonepileptogenic) and epileptogenic hippocampal cortex.