The Study Of EEG-NIRS Coupling Relation On Contralateral Motor Area Under RTMS

Neurovascular coupling(NVC)is a nerve-activating support mechanism that involves the synergistic effects of the nervous system,metabolic system and vascular systems.Repetitive transcranial magnetic stimulation(rTMS)as a nerve stimulation method can excite or inhibit the nerve tissue in the target region or the contralateral brain region,and can be reflected by variety of parameters such as electrophysiology,biochemistry and behavioral science.Previous study on the changes of brain function caused by the rTMS mainly focuses on the changes of electrophysiology or the changes of blood oxygen,but lacks the changes of neurovascular coupling process under rTMS.The combined analysis of electroencephalogram(EEG)and near-infrared spectroscopy(NIRS)under rTMS is important for revealing the coupling relationship between nerve and blood in the process of brain activity.In this paper,the rTMS-EEG and rTMS-NIRS signal acquisition platform is built,and rTMS stimulation experiments are carried out with the frequency of 1Hz and 5Hz.Firstly,EEG changes and blood oxygen changes under rTMS stimulation were analyzed independently.Results showed that the power spectral energy of EEG in the contralateral motor area was decreased slowly after rTMS stimulation,while the blood oxygen concentration was gradually increased and slowly decreased,both of which had rTMS delay effect.Then,the correlation and Granger causality between the electrophysiological and blood oxygen of the contralateral nerve under rTMS stimulation were compared and analyzed.On the whole,the EEG power spectrum has a significant negative correlation with the change of blood oxygen,and there is a significant causal relationship between them.Compared with 1Hz rTMS,5Hz rTMS significantly enhances the correlation and causality between the EEG a and β bands associated with the contralateral and motor areas and the parameters of blood oxygen,and reduces the optimal fitting and order.In conclusion,we infer the main reason for the high frequency rTMS stimulation increasing the correlation between the a and β bands with the parameters of blood oxygen and decreasing the fitting order and enhancing causality is that the high-frequency rTMS stimulation enhances the tightness of the contralateral oxygen coupling to the nerves,so that the coupling of nerve blood oxygen to the complex dispersion tends to be directly coupled.Thus,the causal association between EEG and blood oxygen is enhanced.In this paper,the effects of rTMS on the correlation and causality of nerve blood oxygen were analyzed,and the mechanism of rTMS stimulation frequency on neurovascular coupling was clarified.The results will provide a new method and idea for the study of neurovascular coupling mechanism under the rTMS.