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.

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BackgroundGrammatical encoding is impaired in many persons with aphasia (PWA), resulting in deficits in sentence production accuracies and underlying planning processes. However, relatively little is known on how these grammatical encoding deficits can be mediated in PWA. This study aimed to facilitate off-line (accuracy) and real-time (eye fixations) encoding of passive sentences through implicit structural priming, a tendency to better process a current sentence because of its grammatical similarity to a previously experienced (prime) sentence.MethodSixteen PWA and Sixteen age-matched controls completed an eyetracking-while-speaking task, where they described a target transitive picture preceded by a comprehension prime involving either an active or passive form. We measured immediate and cumulative priming effects on proportions of passives produced for the target pictures and proportions of eye fixations made to the theme actor in the target scene before speech onset of the sentence production.Results and conclusionBoth PWA and controls produced cumulatively more passives as the experiment progressed despite an absence of immediate priming effects in PWA. Both groups also showed cumulative changes in the pre-speech eye fixations associated with passive productions, with this cumulative priming effect greater for the PWA group. These findings suggest that structural priming results in gradual adaptation of the grammatical encoding processes of PWA and that structural priming may be used as a treatment component for improving grammatical deficits in aphasia.

Background: Recent studies suggest older adults’ implicit learning of syntactic patterns remains largely intact. Syntactic priming has proven to be a sensitive tool to examine this implicit sensitivity. However, most priming studies with older adults have focused on production, and none have included an electrophysiological component. This study explores the neural correlates of syntactic priming in older adults’ comprehension. Method: We used a self-paced reading and event-related potential paradigm with groups of older and younger adults. Reduced Relative targets were primed, unprimed, or lexically boosted, while reading times and EEG recordings were obtained. Pre-tests of Working Memory and Processing Speed were also recorded. Results: Older adults showed intact priming and lexical boost on reading times, while lexical facilitation was dependent on syntactic overlap in the older but not the younger group. Syntactic priming was evident on N400 and P600 modulations on verbs and nouns in Reduced Relatives, and generally did not differ by age group. This suggests older and younger adults are equally susceptible to syntactic facilitation, and makes the case for more non-declarative, electrophysiological measurements of older adults’ sentence processing ability in future studies.