Computational model of carbachol-induced delta, theta, and gamma oscillations in the hippocampus.
Field potential recordings from the rat hippocampus in vivo contain distinct frequency bands of activity, including delta (0.5-2 Hz), theta (4-12 Hz), and gamma (30-80 Hz), that are correlated with the behavioral state of the animal. The cholinergic agonist carbachol (CCH) induces oscillations in the delta (CCH-delta), theta (CCH-theta), and gamma (CCH-gamma) frequency ranges in the hippocampal slice preparation, eliciting asynchronous CCH-theta, synchronous CCH-delta, and synchronous CCH-theta with increasing CCH concentration (Fellous and Seinowski, Hippocampus 2000;1 0:187-197). In a network model of area CA3, the time scale for CCH-delta corresponded to the decay constant of the gating variable of the calcium-dependent potassium (K-AHP) current, that of CCH-theta to an intrinsic subthreshold membrane potential oscillation of the pyramidal cells, and that of CCH-gamma to the decay constant of GABAergic inhibitory synaptic potentials onto the pyramidal cells. In model simulations, the known physiological effects of carbachol on the muscarinic and K-AHP currents, and on the strengths of excitatory postsynaptic potentials, reproduced transitions from asynchronous CCH-theta to CCH-delta and from CCH-delta to synchronous CCH-theta. The simulations also exhibited the interspersed CCH-gamma/CCH-delta and CCH-gamma/CCH-theta that were observed in experiments. The model, in addition, predicted an oscillatory state with all three frequency bands present, which has not yet been observed experimentally.
Tiesinga
P H
PH
Sloan Center for Theoretical Neurobiology, Salk Institute, La Jolla, California 92037, USA. tiesinga@salk.edu
Fellous
J M
JM
José
J V
JV
Sejnowski
T J
TJ
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D016477:Artifacts; D002217:Carbachol; D018679:Cholinergic Agonists; D003198:Computer Simulation; D003700:Delta Rhythm / Q000187:drug effects; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007395:Interneurons / Q000502:physiology; D008959:Models, Neurological; D010507:Periodicity; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D013826:Theta Rhythm / Q000187:drug effects
D018679:Cholinergic Agonists; D002217:Carbachol; D000109:Acetylcholine