A corpus-based study of the verb collocations in the Chinese connected speech of Alzheimer’s disease

Previous research regarding verb production deficits in Alzheimer’s disease (AD) primarily concentrated on either the quantity of verbs (inflections) or verb-related semantic units, with little consideration given to verb production within syntactic contexts, i.e., verb collocations. This study explored verb collocations in the connected speech of Chinese AD patients within the framework of dependency syntax. The findings include: (1) The frequency distribution of verb collocation patterns in AD follows the Mixed-Poisson function similar to that in the healthy control elderly (HCE) and healthy control young (HCY) groups, but it differs in the use of low- and high-collocation patterns; (2) In the static aspect, the AD patients exhibit the lowest overall mean collocation pattern (MCP) among the three treebanks, followed by the HCE group. In the dynamic aspect, the MCP and sentence length in the three groups show a similar synergistic relation, but differences exist in the quadratic regression parameters; (3) Based on the probabilistic distribution of verb-governed dependencies, the AD patients exhibit the lowest syntactic proficiency, followed by the HCE group. The differences between the AD patients and the HCE group confirm the presence of verb production deficits and a decline in syntactic proficiency in AD. Although the HCE group also shows mild language deterioration compared to the HCY group, the extent of these changes is considerably smaller than that observed in the AD patients. These findings suggest that while aging may contribute to a partial decline in language abilities, AD markedly exacerbates and accelerates this deterioration process, following a pathological trajectory distinct from normal aging.