Phase-amplitude Coupling Analysis Of Epileptic EEG Signals

Epilepsy is one of the most common neurological disorders affecting 70 million people worldwide,and the analysis of cross-frequency coupling(CFC)during seizures is of great importance for the treatment of epilepsy.Among them,phase-amplitude coupling(PAC),as the most common CFC mode,helps clinicians to predict and control the development of epilepsy patients,which in turn lays the foundation for the development of reasonable and effective antiepileptic drugs,and plays an important role in exploring the pathogenesis of various neurological diseases.Firstly,a new concept of quadratic phase amplitude coupling(QPAC)is innovatively proposed on the basis of PAC,and a new wavelet bicoherence method is constructed for quantification to measure the modulation relationship between the phase of two frequency components of neural oscillation and the amplitude of their frequency sum components.A simulation model is developed using the Von-Mises coupling method,and the performance of the method is evaluated using simulated data.The simulation results show that this method can effectively characterize the coupling strength of QPAC,and it is almost independent of the data length and has good noise immunity.Secondly,the method was applied to the QPAC analysis of intracranial EEG data collected from six epilepsy patients in Xuanwu Hospital of Capital Medical University,and it performed well in determining the seizure process and the onset and termination of seizures compared with the traditional PAC method,which can more effectively characterize the changes of coupling during the seizure process.As a new biomarker,it provides a potential way to explore the seizure mechanism.Finally,to address the validity of traditional PAC methods,PAC analysis was performed using intracranial EEG signals from 10 epileptic patients collected at the New Delhi Neurological and Sleep Center at different periods,and the inherent features of the signals were found to lead to false identification of PAC during the detection process.Based on this,the extended modulation index method was introduced to distinguish spurious from true PAC and to estimate the statistical significance of phase and amplitude at each pair of frequencies in the whole common-mode map based on extreme value statistics,which provides a more reliable theoretical basis and implementation for accurate analysis of frequency coupling in each seizure period in drug-resistant focal epilepsy.