Syntactic Impairments of Chinese Alzheimer’s Disease Patients from a Language Dependency Network Perspective

This study examined the syntactic impairments of Chinese Alzheimer's disease patients with a dependency network approach. The dependency treebanks and dependency networks are constructed from the discourses of both the patient group and its healthy peers. By analysing the contrasts in the dependency networks of the two groups, we found that 1) the mean dependency distance (MDD) of the AD group is shorter than that of the HP group; furthermore, the MDDs of both AD and HP groups are far below the standard Chinese MDD; 2) the content words like remember, forget, know, etc. and the negative forms of the verbs like don't know, can't remember, can't say, etc. show highly repetitive uncertain and negative expressions that are typical of the predicates of the clauses of AD patients; 3) the function word vertices in the AD dependency network have distinctive network parameters such as higher 'betweenness' centrality, closeness centrality, and clustering coefficients, etc., indicating that the syntax of AD is impaired and features more simplified stereotypes. These results indicate that the syntax of the AD group has been impaired from parts of speech to the whole syntactic structure.