| Objective Repeated mild traumatic brain injury(rmTBI)often occurs in various confrontational sports and some military training subjects,studies have shown that the vast majority of cases of rmTBI are subconcussive in severity,this study intends to conduct multi-dimensional research from the level of EEG time-domain and frequency-domain,task-state and resting-state,in order to clarify the neuroelectrophysiological mechanism of subconcussive rmTBI affecting working memory processing and the characteristics of resting-state EEG microstate.Methods In this study,professional boxers who met the inclusion criteria were selected as subjects in the rmTBI group,and matched healthy subjects as the control group.By employing the real-world objects images as working memory encoding elements,we designed and performed a modified sternberg paradigm with multiple loading levels.The resting-state 64-channel EEG signals were collected under the condition of resting and closed eyes,the task-state EEG data was recorded simultaneously during performing the paradigm.By employing neuropsychological assessment methods,and combining with the characteristics of behavioral parameters of working memory,we used event-related potentials(ERPs)technology to analyze the components of N100,N200,P300 and FCSW in working memory processing at different loading levels,and the event-related spectral perturbation(ERSP)technology was employed to study the time-frequency oscillation characteristics of theta,alpha,and beta frequency bands induced by working memory processing at different loading levels,moreover,we used the microstate technology to analyze the whole-brain dynamic topological pattern of resting-state EEG,in order to explore the time-domain and frequency-domain mechanism of rmTBI affecting working memory and the electrophysiological characteristics of the dynamic operation pattern for brain functional networks.Results Neuropsychological assessment showed that the rmTBI group had normal general cognitive function and intellectual status.Behavioral research on working memory showed that the rmTBI group had significantly weakened behavioral parameters of working memory at higher loading levels.ERPs studies suggested that the rmTBI group has significantly weakened P300 and FCSW components during working memory encoding process,and the FCSW components in the rmTBI group could not be efficiently and dynamically adjusted with the increase of loading levels;during the retrieval and decision-making process,the N200 and P300 components of the rmTBI group were significantly decreased,and the P300 component was significantly negatively correlated with the reaction time of retrieval and decision-making,which suggested that the P300 component played a key role in working memory processing for the real-world objects.Time-frequency analysis showed that the rmTBI population exhibited significantly altered time-frequency power of frontal theta-band event-related synchronized oscillations(ERS),parieto-occipital alpha-band event-related desynchronized oscillations(ERD),and frontal low beta-band ERS;moreover,low beta ERS were significantly negatively correlated with behavioral characteristics in both groups,which indicated that the post-retrieval control function of working memory and recovery efficiency could have a direct impact on working memory behavior.Therefore,the significantly altered low-frequency neural oscillations such as theta,alpha,and low beta frequency bands were the key time-frequency mechanisms of working memory dysfunction for the rmTBI sufferers.The resting-state EEG microstate analysis demonstrated that the rmTBI group did not show significant abnormal changes in the EEG topology that could reflect basic brain function,however,the duration of microstate classes A,B,and D were significantly shorter than that of the control group,and the occurrence of microstate class C within unit time was significantly increased,which suggested that the dynamic operation pattern of the brain functonal network in rmTBI sufferers had a characteristic disorder.Conclusion Combining neuropsychological and working memory behavioral research,this study was the first to reveal the EEG time-domain and frequency-domain mechanisms by which rmTBI affects working memory processing and the resting-state EEG microstate characteristics of the rmTBI population,and contributed the research basis and multi-dimensional evidence to the innovation of the evaluation and intervention system of the working memory function and brain functional network for the rmTBI sufferers. |
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