Intrahippocampal gamma and theta rhythm generation in a network model of inhibitory interneurons

Hippocampal theta and gamma rhythms often occur together. While gamma activ ity is supposed to be generated intrahippocampally, the source of theta osc illations is still debated. Here, a network model of hippocampal inhibitory interneurons was capable of generating the gamma rhythm when responding to constant excitation. Adding a periodic term to this stimulation resulted i n complex pattern generation of the network, also including a theta frequen cy periodicity in the time dependent network coherence measure. A pyramidal cell model driven by the output of this network proved that membrane poten tial oscillations in the theta range can be entrained by this intrahippocam pal mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.