Electrical Signal-based Brain Function Closed-loop Modulation System And Its Application

With the development of brain science,closed-loop brain function modulation technology that effectively combines brain function monitoring and modulation has become the hot spots in this field.Among the monitoring methods,Electroencephalogram(EEG)is a brain imaging technology widely used in experimental research and clinical application because of its high temporal resolution,easy operation and low cost of use and maintenance.Among the modulation methods,Transcranial electrical stimulation(t ES)technology has broad application prospects because of its safety,non-invasiveness and portable characteristics.The effective combination of the above two technologies enables real-time monitoring and simultaneous evaluation of brain function,thereby realizing precise modulation of brain function.However,if the existing equipment is directly used in combination,there would be problems such as "difficulty in compatibility"(such as easy saturation of the analog part of the EEG equipment,mutual interference between acquisition and stimulation equipment)and "difficulty in synchronization"(such as poor synchronization between the equipment).Aiming at these problems,this dissertation develops high-performance EEG equipment,low-noise t ES equipment and synchronization device for closed-loop modulation.The specific contents are as follows:1.Aiming at the problem that EEG signals were easily interfered by t ES when combined with t ES and EEG acquisition,the bipolar lead,wide voltage rail,and dynamic DC suppression technology were used to solve the saturation problem of EEG equipment under the t ES.Combined with adaptive common-mode noise suppression technology,the ability of EEG equipment to suppress common-mode noise was improved.The software of EEG equipment under Windows operating system was developed.Subsequently,the performance test of EEG equipment and the experimental verification compared with commercial equipment were carried out.The performance results indicated that the relevant indicators of the equipment had reached the level of internationally advanced equipment.Some indicators even surpassed those of similar international equipment.The comparative verification experiment indicated that the compatibility of the equipment with baseline drift and t ES artifact was greatly improved compared to commercial equipment.These results showed that the developed EEG equipment had good compatibility.2.Based on the developed EEG device,the effects of action real time strategy games on brain cognitive function were studied.A dual choice auditory go/no-go task study was conducted for game experts and amateurs.Using the lateralized readiness potential as indicators of partial information transfer,the relationship between the game experience and information transfer was discussed.The results suggested that game experts and amateurs might use different information transfer modes,and the game experts had a higher rate of task correctness.This study indicated that the EEG device developed in this dissertation could effectively capture task-related brain information and could be used for brain research.3.Aiming at the problem of strong t ES interference to EEG equipment when combined t ES and EEG acquisition,a t ES equipment with high accuracy,low noise,multi-channel,and accurate control of action time and signal phase was designed by using enhanced Howland current source,direct digital signal synthesis and multi-channel output time-phase precise control technology.The performance test of the t ES equipment indicated that the t ES equipment had better linearity,accuracy and other performance indicators.In view of the compatibility problem,the comparison experiment with the commercial equipment and its combined system indicated that the EEG signal obtained by the combined t ES and EEG equipment developed in this dissertation was better in terms of harmonics and noise.In the joint modulation of the left and right dorsolateral prefrontal targets,the system built by the developed equipment showed better compatibility than the system built by the commercial equipment.These results indicated that the relevant techniques introduced in the development of t ES equipment were effective in improving the compatibility of combined t ES and EEG acquisition.4.Based on the developed t ES equipment,the effects of transcranial direct current stimulation(t DCS)and transcranial alternating current stimulation(t ACS)on event related desynchronization in motor imagery were compared.Specifically,the generative adversarial network and the multi-output convolutional neural network algorithm were used for motor imagery classification,and the classification results under different stimulus conditions were statistically analyzed.The results indicated that both t DCS and t ACS methods could effectively improve the classification accuracy of the motor imagery-based brain computer interface.This study suggested that the developed t ES equipment could be used for brain function modulation research.5.Aiming at the time synchronization between EEG equipment and t ES equipment during closed-loop modulation,a synchronization device with the precise time-locking control technology was developed to achieve time synchronization between multiple EEG equipment and t ES equipment.Furthermore,a closed-loop brain function modulation system based on electrical signals was built,which was composed of the developed EEG equipment,t ES equipment and synchronization device.Through the performance tests of the synchronization device and the research work of the commercial equipment construction system,it was proved that the device solved the synchronization problem between the devices.The system in this dissertation had certain advantages in the synchronization of closed-loop modulation.Through the performance test of the synchronization device and a review of literature research of the research work based on the commercial equipment,it was proved that the device could better solve the synchronization problem between the equipment.6.Based on the developed brain function closed-loop modulation system,the research on sleep modulation by t ACS was carried out.A 60 person-times 5Hz-t ACS sleep modulation experiment was completed.Through the comparative analysis of the spindle wave events and the results of sleep staging,it was shown that applying lowfrequency t ACS between the left and right dorsolateral prefrontal cortex could promote the subjects to enter sleep homeostasis faster.Furthermore,a 24 person-times closed-loop sleep modulation experiment with brain state dependent variable-frequency t ACS was completed.In this modulation experiment,the system identified the subjects entering a steady state of sleep and triggered variable-frequency stimulation.The results showed that variable-frequency t ACS could promote the subjects to enter deep sleep faster.This study proved that the system developed in this dissertation could be applied to the research of the brain function closed-loop modulation.In conclusion,focusing on the needs of closed-loop brain function modulation,this dissertation designed EEG equipment,t ES equipment and synchronization device,and solved the compatibility and synchronization problems of combined EEG and t ES to carry out closed-loop regulation of brain function.A closed-loop brain function modulation system based on electrical signals was constructed,and it was tested through research on brain-computer interface,cognitive-evoked EEG extraction and sleep modulation,which confirmed the applicability of the developed equipment and system.The developed system had certain practical value.