Alzheimer's disease (AD) is a progressive neurodegenerative disease characterised by cognitive decline, including impaired memory and language skills. Previous research has extensively studied language deficits in the disease, but language difficulties, syntactic complexity and pronoun use in Slovene, a morphologically rich language, have received less attention. The aim of this study is to investigate the mentioned aspects by analysing the spontaneous speech of Slovenian speakers with AD and comparing it with the speech of neurologically healthy subjects. The present study focuses on the frequency and types of linguistic errors, the syntactic complexity of sentences and the frequency of use of different types of pronouns.
Participants diagnosed with mild to moderate forms of AD and neurologically healthy individuals performed a picture description task based on a picture entitled Cookie theft picture. Samples of spontaneous speech were transcribed and analysed for the proportion and type of linguistic errors, syntactic complexity (sentence length, sentence type, preposition-subordination ratio) and the use of (different types of) pronouns.
People with AD made significantly more linguistic errors compared to healthy participants (p = 0.02), especially semantic errors such as semantic paraphasias (p = 0.004), while syntactic errors were more frequent in the control group (p = 0.006). Syntactic simplifications were also evident in individuals with AD, as they formed shorter sentences (p < 0.01) with fewer clauses (p < 0.01). However, people with AD used subordinators statistically significantly more often than healthy individuals (p = 0.04). In addition, the use of pronouns was significantly more frequent in the group of people with AD (p = 0.004), while no significant differences were found for the individual types of pronouns used. The findings are consistent with previous research highlighting semantic impairment as a key linguistic marker of AD, and suggest that language deficits in the disease may be associated with underlying memory impairments, particularly semantic and working memory.
Our study contributes to the understanding of language disorders in Slovenian-speaking people with AD and helps to enable cross-linguistic research in this field. The results are of potential practical value in attempts to diagnose the disease earlier and, consequently, to intervene earlier. Future research could also use a longitudinal approach to follow changes in spontaneous speech over time, which would provide deeper insights into the progression of language decline in AD.
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