Idiom Comprehension in Alzheimer’s Disease: The Role of Idiom Dimensions, Task Types and Executive Functions

Introduction&Aims
Idioms are expressions whose meaning cannot be deduced solely from their constituent words. Their linguistic complexity influences brain processing (Papagno, 2010). Idiom comprehension relies on executive functions (EFs), requiring the activation of literal and figurative meanings and inhibiting literal interpretations to access figurative ones. However, it is unclear whether all idioms rely equally on EFs.

Alzheimer’s disease (AD), a neurodegenerative condition affecting memory and cognition (Wray, 2011), often presents with memory disturbance, word-finding issues, and difficulty learning new information, progressing to impair executive functions and multitasking. AD patients struggle to inhibit automatically activated literal meanings, suggesting idiom comprehension may be impaired. However, idiom familiarity, frequency, ambiguity, decomposability, transparency and predictability may influence comprehension patterns.
This review investigates: (a) whether idiom comprehension deficits in AD vary depending on idiom characteristics, (b) how task selection may affect performance, and (c) links between idiom comprehension and EFs in AD.

Methodology
This review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines (PRISMA). After the screening phase, 11 studies were analysed. We extracted information about patients’ characteristics, idiom characteristics, linguistic tasks, executive test scores, scores for other relevant psychometric tests, and idiom comprehension outcomes.

Results&Discussion
Findings suggest idiom dimensions modulate comprehension in AD. Opaque idioms were easier, while ambiguous and unambiguous idioms posed challenges. Transparent and unambiguous idioms were less demanding. Task choice significantly affected results, with string-to-picture matching tasks potentially overestimating deficits. EF and memory retrieval roles in idiom comprehension appear on a continuum. Ambiguous and decomposable idioms might demand more EF involvement for resolving ambiguity and semantic links, while unambiguous, opaque idioms may rely more on mental lexicon retrieval. Last, tailoring tasks to patients’ cognitive abilities is crucial to accurately assess idiom comprehension in AD.

Papagno, C. (2010). Idiomatic language comprehension: Neuropsychological evidence. In Neuropsychology of communication (pp. 111-129). Milano: Springer Milan.

Wray, A. (2011). Formulaic language as a barrier to effective communication with people with Alzheimer`s disease. Canadian Modern Language Review, 67(4), 429-458.