Sang-Gui Lee

Stability analysis on beta rhythm in CA1 region

Rhythms in the gamma range and the beta range are associated with attention, perception, and cognition. Therefore, the mechanism of how long-distance synchrony between participating sites is achieved becomes one of the important issues of neuroscience. With the help of the phase oscillator model, the stabilities of phase-locked states of beta rhythm are studied for individual synaptic connections between two neuronal units including an excitatory and an inhibitory neuron. From the linear combination of stability functions, we can understand the role of each connections. The temporal behavior of numerically simulated models also shows the validity of our phase model studies. We also show that this method is also applicable for the delayed synaptic connection.

Parameter dependence of stochastic resonance in the stochastic FitzHugh-Nagumo neuron

Recently, the phenomena of stochastic resonance (SR) have attracted much attention in the studies of the excitable systems, in particular, the nervous system, under inherent noise. We study SR in a stochastic FitzHugh-Nagumo (FHN) neuron under Ornstein-Uhlenbeck noise and periodic stimulus, focusing on the dependence of SR phenomena on the stimulus parameters. Similar to the case of the Hodgkin-Huxley neuron, we find that the dependence of the critical forcing amplitude, above which resonance disappears and optimal noise intensities with maximal amplification of periodic stimulus, on the frequency of the periodic stimulus shows a bell-shaped structure with a minimum near the natural frequency. This frequency dependence of SR is explained in connection with the firing onset bifurcation curve of the FHN neuron in the deterministic situation. We also find that the critical forcing amplitude and optimal noise intensity of the stochastic bistable system has a monotonous structure which are also explained throu...