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

Hippocampal theta and gamma rhythms often occur together. While gamma activity is supposed to be generated intrahippocampally, the source of theta oscillations 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 in complex pattern generation of the network, also including a theta frequency periodicity in the time dependent network coherence measure. A pyramidal cell model driven by the output of this network proved that membrane potential oscillations in the theta range can be entrained by this intrahippocampal mechanism. 2001 Elsevier Science B.V. All rights reserved.