Bifurcation Analysis And Closed-loop Control Of A Absence Epilepsy Model

Epilepsy is a common neurological disorder that threatens the health of tens of millions of people around the world and creates a heavy medical burden and growing social problems.Absence epilepsy(AE),one kind of the refractory epilepsy,is drug-resistant and unsuitable for surgery.Electrical stimulation techniques,such as deep brain stimulation and transcranial current stimulation,have shown certain success on regulating nervous system diseases,however,the underlying mechanisms have not been fully understood.Moreover,the current clinical electrical stimulation therapy is generally open-loop electrical stimulation,which is insufficient in flexibility and adaptability.Therefore,this paper constructs a model-based closed-loop electrical stimulation strategy,which studies the inhibition of absence seizures from three aspects: model establishment,mechanism analysis and closed-loop control.Firstly,we analyze the physiological structure and brain position of the absence epilepsy and establish the thalamo-cortical model of absence seizures.We ensure the model can simulate the normal and pathological discharge activities and determine the corresponding model parameters for normal and abnormal output to achieve the construction of typical physiological activities during the absence seizures.Then,according to the latest experimental results,the interaction between cortical excitation and thalamic feed-forward inhibition has an important effect on absence seizures.Therefore,we perform single-parameter,two-parameter and multi-parameter bifurcation analysis on the transition of the model state and its dynamics in the corresponding parameter space.It is found that the onset of absence epilepsy is closely related to the Hop bifurcation and double-limit bifurcation of the model dynamics,which reveals the dynamic mechanism and potential physiological mechanism of absence seizures.Finally,due to the uncertainty of the inhibition effect of open-loop pulse stimulation on absence seizures,we propose to combine feedback control,radial basis function neural network and sliding mode control together to construct a closed-loop robust control strategy.It eliminates the effects of parameter changes,external disturbances,various un-modeled dynamics and achieves effective suppression of absence seizures.The results of this study further reveal the potential mechanism of absence seizures and realize the closed-loop adaptive control theory design of absence seizures,which provides important theoretical guidance for the experimental research and clinical application of electrostimulation-based absence seizure control.