Ionic mechanisms for intrinsic slow oscillations in thalamic relay neurons.
The oscillatory properties of single thalamocortical neurons were investigated by using a Hodgkin-Huxley-like model that included Ca2+ diffusion, the low-threshold Ca2+ current (lT) and the hyperpolarization-activated inward current (lh). lh was modeled by double activation kinetics regulated by intracellular Ca2+. The model exhibited waxing and waning oscillations consisting of 1-25-s bursts of slow oscillations (3.5-4 Hz) separated by long silent periods (4-20 s). During the oscillatory phase, the entry of Ca2+ progressively shifted the activation function of lh, terminating the oscillations. A similar type of waxing and waning oscillation was also observed, in the absence of Ca2+ regulation of lh, from the combination of lT, lh, and a slow K+ current. Singular approximation showed that for both models, the activation variables of lh controlled the dynamics of thalamocortical cells. Dynamical analysis of the system in a phase plane diagram showed that waxing and waning oscillations arose when lh entrained the system alternately between stationary and oscillating branches.
Destexhe
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Howard Hughes Medical Institute, Computational Neurobiology, Laboratory, La Jolla, California 92037.
Babloyantz
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A
Sejnowski
T J
TJ
D000818:Animals; D001683:Biological Clocks; D055592:Biophysical Phenomena; D001703:Biophysics; D002118:Calcium / Q000378:metabolism*; D002415:Cats; D007700:Kinetics; D008564:Membrane Potentials; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D013788:Thalamus / Q000166:cytology / Q000502:physiology*
D011188:Potassium; D002118:Calcium