Research On The Brain Activity During Working Memory Maintenance Based On The TMS And EEG

Working memory (Working Memory WM) is a resource limited memory system for temporary storage and processing of brain information in the process for executing the cognitive task. It can be divided into coding information, maintenance information, making decision and other processes. Among them, maintaining the information is entiredly internal brain activity, without inputing any external information. The research on the brain activity of the memory maintence which can reveal the brain areas involved in the process and the cooperation between the different brain regions.Using the rTMS responsed for interposing the brain area with the EEG, the activities of the brain areas were studied by extracting the energy and phase characteristics of EEG signals in the relevant frequency band. The research focus on the activities of the parietal cortex in the task, by comparing the activities of the left and right brain regions, and explored the effect of rTMS for stimulating the parietal lobe of the brain at the stage of "memory maintence".First of all the research used the experimental paradigm of different memory load for determining brain areas for "information maintence". After that, the research used the experimental paradigm of different memory load again, and stimulated the related brain area of the subject during the "information maintence "phase for research the effect of the rTMS for the brain activity.The results of behavioral data analysis showed that with the increase of the memory load, the accuracy of the rTMS was decreased, and the reaction time was significantly increased at the same time. The reaction time was significantly shorter than that of the pseudo rTMS.The EEG data analysis results show that:with increasing memory load, theta band power spectrum energy increases the area mainly prefrontal and parietal brain areas and alpha band power spectrum energy decreased mainly in the left parietal region; And with increasing memory load, theta band event related synchronization phenomenon is more and more obvious, extending to the right from the left prefrontal cortex and parietal cortex, the alpha band events related to desynchronization is more and more obvious phenomenon appears, to desynchronize the same range from the left prefrontal and parietal lobe to the right expansion. As the memory load increased, the phase synchronization between the two bands of the signal in the prefrontal lobe and the parietal lobe was enhanced. The brain activity of the parietal cortex has been significantly changed in the real rTMS; two band signals reflected the connectivity between the left parietal lobe and left prefrontal enhanced. At the same time, the connectivity between the lateral parietal also enhanced. The results also showed that the connectivity between the left parietal lobe and the prefrontal lobe was enhanced by the average cluster coefficient of the prefrontal and parietal lobes, the network’s average cluster coefficient, and the intermediate center.Conclusion:1. the left prefrontal lobe and the parietal lobe are the key areas to participate in the "information maintence" stage of working memory, and rTMS is more active in the parietal cortex during the "information maintence" phase of the brain; 2. With memory load increasing, the right brain area gradually participated in the "information maintence" brain activity, suggesting that the right brain region maybe compensate to the left brain region, this compensation effect is more and more obvious with the memory load increasing.3. With memory load increasing, the connectivity between the left prefrontal lobe and the parietal lobe has also enhanced, parietal. The connectivity between the prefrontal lobe and the parietal lobe is more obvious after stimulating the parietal lobe, and the parietal lobe more played a role in the transmission of information. It suggested that rTMS could activate the parietal cortex, and indirectly activate the prefrontal cortex through the information transfer of the parietal cortex, which played a positive role in the efficiency of "information maintence" in working memory...