Details about the structure of a network model are revealed at the spontaneous spike activity level,in which the power-law of synchrony is optimized to that observed in the CA3 hippocampal slice cultures.The network m...Details about the structure of a network model are revealed at the spontaneous spike activity level,in which the power-law of synchrony is optimized to that observed in the CA3 hippocampal slice cultures.The network model is subject to spike noise with exponentially distributed interspike intervals.The excitatory(E)and/or inhibitory(I)neurons interact through synapses whose weights show a log-normal distribution.The spike behavior observed in the network model with the appropriate log-normal distributed synaptic weights fits best to that observed in the experiment.The best-fit is then achieved with high activities of I neurons having a hub-like structure,in which the I neurons,subject to optimized spike noise,are intensively projected from low active E neurons.展开更多
The interesting task here is to study the frequency-current(f–I)curve and phase response curve(PRC),subject to neural temperature variations,because the f–I curve and PRC are important measurements to understand dyn...The interesting task here is to study the frequency-current(f–I)curve and phase response curve(PRC),subject to neural temperature variations,because the f–I curve and PRC are important measurements to understand dynamical mechanisms of generation of neural oscillations,and the neural temperature is widely known to significantly affect the oscillations.Nevertheless,little is discussed about how the temperature affects the f–I curve and PRC.In this study,frequencies of the neural oscillations,modulated with the temperature variations,are quantified with an average of the PRC.The frequency gradient with respect to temperature derived here gives clear classifications of the PRC,regardless of the form.It is also indicated that frequency decreases with an increase in temperature,resulted from bifurcation switching of the saddle-homoclinic to the saddle-node on an invariant circle.展开更多
Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big ...Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltagegated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.展开更多
基金Supported by the Grant-in-Aid for Challenging Exploratory Research(No 25540110)from MEXT.
文摘Details about the structure of a network model are revealed at the spontaneous spike activity level,in which the power-law of synchrony is optimized to that observed in the CA3 hippocampal slice cultures.The network model is subject to spike noise with exponentially distributed interspike intervals.The excitatory(E)and/or inhibitory(I)neurons interact through synapses whose weights show a log-normal distribution.The spike behavior observed in the network model with the appropriate log-normal distributed synaptic weights fits best to that observed in the experiment.The best-fit is then achieved with high activities of I neurons having a hub-like structure,in which the I neurons,subject to optimized spike noise,are intensively projected from low active E neurons.
基金Supported by the Grant-in-Aid for Challenging Exploratory Research from MEXT(No 25540110).
文摘The interesting task here is to study the frequency-current(f–I)curve and phase response curve(PRC),subject to neural temperature variations,because the f–I curve and PRC are important measurements to understand dynamical mechanisms of generation of neural oscillations,and the neural temperature is widely known to significantly affect the oscillations.Nevertheless,little is discussed about how the temperature affects the f–I curve and PRC.In this study,frequencies of the neural oscillations,modulated with the temperature variations,are quantified with an average of the PRC.The frequency gradient with respect to temperature derived here gives clear classifications of the PRC,regardless of the form.It is also indicated that frequency decreases with an increase in temperature,resulted from bifurcation switching of the saddle-homoclinic to the saddle-node on an invariant circle.
基金Supported by JST,CREST,and JSPS KAKENHI under Grant No 15H05919
文摘Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltagegated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.
