Deficiency Of Brain Language Functional Network In Patients With Mild Cognitive Impairment:A Research Based On EEG Analysis

Mild cognitive impairment(MCI),a clinical state intermediate between normal aging and dementia,is characterized by deterioration in memory and cognitive functions,even though it does not affect day-to-day activities.MCI is a potential precursor of Alzheimer's disease(AD).As a neurodegenerative disease,the onset of AD is hard to detect and the courses are slow and irreversible.Once that happens,patients will suffer from severe losses in memory and disorders in language and other cognitive functions.They may even lose the ability to take care of themselves until the end of their lives.Considering these devastating effects,it is of great significance to detect the early and typical signs associated with MCI,so as to prevent it from developing into AD and to delay its progression.Language deficits,one of the most significant clinical symptoms of MCI,are closely related to all stages of the dementia.Yet,the neural mechanisms of the speech and language disorders associated with MCI is not fully understood.Specifically,there is still a knowledge gap in how language productions are affected by MCI.With that in mind,the motivation of the present study is to bridge these gaps using analysis of brain functional network,aiming to provide valuable information for the early detection of the disease.The present study covers two cognitive processes,word preparation and working memory,which are related to the clinical features of MCI.Correspondingly,two experimental paradigms,picture naming and N-back,were used to collect electroencephalography(EEG)signals.Behavioral and event-related potential(ERP)responses were analyzed,together with the construction of brain functional network in patients with MCI and those that are cognitively intact.By establishing the model of impaired functional network,the present study aims to reveal how the disrupted network affects speech,language and memory processes.In this study,two experimental paradigms were first designed to collect EEG signals,followed by the preprocessing of data.After determining the epochs in which the cognitive processes occur,behavioral and ERP analysis were conducted.Thebehavioral results showed that the differences between the two groups of subjects in picture naming and working memory tasks were mainly in accuracy,while the differences in ERP components were mainly in working memory.The PLV-based cortical brain functional network was also constructed after source reconstruction.On this basis,topological attributes of brain functional network in patients with MCI and healthy controls were compared.The differences in clustering coefficient and characteristic path length in patients with MCI compared with the healthy control group indicated that semantic processing and working memory capacity were impaired.Combined with the differences in behavior and ERP,the results indicate that the abnormalities of brain functional network in patients with MCI may stem from the dysfunction of local brain functions.