Research On Mental Fatigue Based On Cross Frequency Couping

Mental fatigue causes the reduction of alertness and work memory,and seriously affects people's normal work and quality of life.At present,there is no unified objective standard for the detection of mental fatigue,and its mechanism is not clear.Cross frequency coupling was used to analyse EEG among different brain areas and different frequency before and after mental fatigue,in order to explore the reasons of cognitive change caused by mental fatigue,and to seek a new objective detection standard of mental fatigue.Firstly,Delta,theta,alpha,beta and gamma frequency bands were extracted,and single channel EEG of each subject before and after mental fatigue was analyzed by three different cross frequency coupling methods.The results showed that not all bands of single channel cross frequency coupling were significantly different after fatigued,only phase phase coupling between theta,delta and gamma had significantly decreased after fatigued.Secondly,cross frequency coupling of multi-channel EEG of each subject before and after mental fatigue were analysed.The results show as below:1,amplitude amplitude coupling of multi-channel EEG in five bands changed after fatigued,network connection density of the brain network constructed by amplitude amplitude coupling of delta band increased significantly,while network connection density of the brain network constructed by amplitude amplitude coupling of theta,alpha,beta and gamma bands significantly reduced.2,phase phase coupling of multi-channel EEG in five bands changed after fatigued,network connectivity density of the brain network constructed by phase phase coupling in five bands is significantly reduced after fatigued.3,phase amplitude coupling of multi-channel EEG between theta,delta and gamma significantly changed.After fatigued phase amplitude coupling between theta and gamma in many regions were significantly decreased,and had asymmetry phenomenon between left brain and right brain;and phase amplitude coupling between all brain regions' delta band and prefrontal,frontal lobe,parietal lobe and occipital region's gamma band significantly changed after fatigued.It shows that phase phase coupling significant changes in different brain regions after fatigued,indicating that mental fatigue may cause the changes of information exchange mechanism,and affect the information exchange process;not all brain regions' phase amplitude coupling changed after fatigued,indicating that cognitive function changes of mental fatigue may be caused by the changes of phase amplitude coupling in related brain areas.The results are of great significance and have practical value in exploring the process of information exchange among brain regions and explaining the causes of cognitive changes induced by mental fatigue.