Sentence comprehension in ageing and Alzheimer's disease

The ability to correctly interpret complex syntax and long sentences is gradually impaired as people age. Typical ageing is characterised by working memory deficits, which are thought to play an important role in determining whether syntax can be comprehended correctly, and neurodegenerative conditions such as Alzheimer's disease (AD) are thought to exacerbate these limitations. Furthermore, declines in processing speed appear to cause increasing difficulty in the proper allocation of cognitive resources necessary for sentence processing. Typically ageing adults may compensate for these deficits successfully when interpreting sentences using semantics or intact cognitive functions, but AD patients may exhibit deficits too severe for this to occur. The causes of syntax comprehension deficits in Alzheimer's are still contested, and may consist of language-specific impairments or deficits in general cognition impacting linguistic behaviour. In this review, we aim to give an overview of the main markers of cognitive ageing and AD in the domain of sentence comprehension, as well as discuss potential underlying factors that may affect sentence comprehension in older speakers and Alzheimer's patients.