Production of different types of familiar expressions by individuals with left- and right-hemisphere damage across discourse elicitation tasks

This study aimed to explore the production of familiar expressions (e.g. idioms, proverbs and pause fillers), including different subtypes, and their variation across different types of elicited discourse in individuals with aphasia due to left hemisphere damage (LHD) and those with right hemisphere damage (RHD) to healthy control (HCs). Twenty-nine individuals (12 with LHD, 8 with RHD and 9 HCs) provided elicited discourse samples during four tasks (free speech, picture description, story narrative and procedural tasks) from TalkBank (AphasiaBank and RHDBank). Familiar expressions were categorised into two broad types: nuanced (conveying emotional or attitudinal meaning) and non-nuanced (literal and speech-flow enhancing). Results showed that individuals with LHD produced more familiar expressions, especially nuanced ones, than those with RHD or HCs. A correlation was found between aphasia severity and the production of familiar expressions, with individuals who had more severe language impairments producing a higher proportion of familiar expressions in some tasks. No significant task differences in familiar expression production were observed among the groups. This study revealed that brain damage affects the production of familiar expressions, with individuals with LHD using them more frequently and in a more nuanced manner. In contrast, individuals with RHD had difficulty producing familiar expressions. Clinically, this underscores the importance of considering hemisphere-specific deficits when assessing and treating language impairments in individuals with brain damage, as therapies may need to be tailored to address the distinct challenges faced by individuals with LHD versus RHD.