Nonlinear And Complex Network Theory In The Application Of EEG Data Analysis Research

The complex connection in human brain exists both in the static anddynamic activities. Different brain neurons, neural ensembles and brain regionscoordinate and interact among each other at kinds of time-space scales, forminga nonlinear and highly complex network on which all the cognitive functions ofbrain are based. EEG signals are the biological signals of the complexsystem-brain. In recent years, applying nonlinear dynamics and complexnetwork theory in EEG signal analysis, identifying the coupling relation amongthe different brain regions and the variety pattern of topology of brain networkat different state have become the hotspots of the multidisciplinary study. Thenonlinear dynamics and complex network theory provide a new perspective forthe study of the complex system-the brain.This study analyzes and improves the nonlinear test methods of time series,testing the nonlinearity of EEG data, analyzes the synchronization in the brainfrom different perspectives, and discusses the construction and analysis methodsof the EEG functional brain network. Basing on the EEG data of alcoholics, thispaper explores the variety pattern of brain dynamics in the state of brain diseasethrough the analysis of synchronization and nature of brain network, identifying the brain synchronization and network nature of the alcoholics under the state ofneurodegeneration disease and their differences with the normal persons. Thispaper also identifies the physiological indicators for the diagnosis of alcoholicsat the early phase by means of machine learning algorithms.This paper has following innovations:(1) Proposing two new nonlinear test methods of time seriesThe characteristic values adopted in the traditional nonlinear test methodshave certain defects. This paper proposes two new nonlinear test methods whichare based on the SampEn and FuzzyEn, and tested the accuracy and efficiencyof these two methods through simulation datasets. Compared to the traditionalmethods, the new methods have the similar accuracy, while much higherefficiency.(2) Proposing a new synchronization analysis method by means ofsource localization technique of EEGThe synchronization analyses in present study on EEG synchronization arealmost all based on the scalp EEG data. However, due to the volume conductoreffect, there may be pseudo relevance between the scalp electrodes, whichfurther affects the measurement of synchronization. This study measures thesynchronization of custom ROI on the cerebral cortex by using the latest sourcelocalization technique of EEG. After comparing two synchronization analysismethods by using the alcoholic data, we found that the EEG synchronizationanalysis method by means of source localization technique can measure the dynamics of cerebral cognitive activities much more accurate.(3) Proposing a new threshold selection method for brain networkconstructionWhen an unweighted and undirected network is constructed, an appropriatethreshold is needed to be set to convert the correlation matrix into binary matrix.The present studies mainly discuss the topology of the network by singlethreshold, while this study proposes a new threshold selection method for theEEG brain network construction, calculating sparsity range as the thresholdspace using the small-world property of the network, and then analyzing thechanges of topology of the network in the threshold space.(4) First using the complex network theory to construct and analyze theEEG functional network of alcoholicsIn present studies on the alcoholics EEG, the features such as energy,power spectrum, and entropy of certain channel or region are adopted. In thisstudy, the complex network theory is firstly used to construct and analyze theEEG functional brain network, identifying the differences of topology of brainnetworks between the alcoholics and normal subjects, demonstrating thefunctional damage of alcoholics’ brains from a new perspective.To sum up, adopting the nonlinear dynamics and complex network theory,this study focuses on the study of synchronization analysis method andconstruction and analysis method of the brain network, discussing the changelaw of the brain synchronization and topology of brain network under the alcoholic state, providing new perspective and evidences for the brain damagewhich may caused by alcoholism. This is a new research achievement of themultidisciplinary study.