Interspike interval statistics in the stochastic Hodgkin-Huxley model: coexistence of gamma frequency bursts and highly irregular firing.
When the classical Hodgkin-Huxley equations are simulated with Na- and K-channel noise and constant applied current, the distribution of interspike intervals is bimodal: one part is an exponential tail, as often assumed, while the other is a narrow gaussian peak centered at a short interspike interval value. The gaussian arises from bursts of spikes in the gamma-frequency range, the tail from the interburst intervals, giving overall an extraordinarily high coefficient of variation--up to 2.5 for 180,000 Na channels when I approximately 7 microA/cm(2). Since neurons with a bimodal ISI distribution are common, it may be a useful model for any neuron with class 2 firing. The underlying mechanism is due to a subcritical Hopf bifurcation, together with a switching region in phase-space where a fixed point is very close to a system limit cycle. This mechanism may be present in many different classes of neurons and may contribute to widely observed highly irregular neural spiking.
Rowat
Peter
P
Institute for Neural Computation, University of California at San Diego, La Jolla, CA 92093, USA. prowat@ucsd.edu
D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology* / Q000528:radiation effects; D017711:Nonlinear Dynamics; D016011:Normal Distribution; D010507:Periodicity; D011336:Probability; D015222:Sodium Channels / Q000502:physiology; D013269:Stochastic Processes; D013997:Time Factors
D015222:Sodium Channels