Dissociating language switching from executive control in bilinguals with MCI

Bilingual language control is a dynamic cognitive system that enables individuals to effectively manage language use and prevent interference when switching between languages. Research indicates that certain neurodegenerative conditions may influence language-switching abilities or hinder the suppression of cross-language interference. However, it remains uncertain whether neurodegeneration primarily affecting mesial temporal structures, such as Mild Cognitive Impairment (MCI), impacts lexical retrieval in dual-language naming conditions. To investigate this, we assessed early and highly proficient Catalan-Spanish bilinguals with MCI (n = 28) and age-matched older adults without MCI (n = 40) in a language-switching task. Additionally, to explore the domain specificity of language control deficits, participants completed four executive control (EC) tasks: task switching, n-back, Spatial Stroop, and flanker task. Results indicated that MCI patients exhibited larger switch costs (switch minus repeat trials) compared to older adults while showing similar mixing costs (repeat minus single trials). In the non-linguistic control domain, MCI patients performed significantly worse than older adults only in the n-back task and displayed slower performance in the task-switching task. However, the regression analysis model incorporating the performance of non-linguistic tasks as predictors of language switching performance did not yield statistically significant results. These findings suggest that reactive control, which involves bottom-up, transient, and stimulus-driven processes, might be independently affected from proactive control, defined as a top-down and sustained control process. Nonetheless, the presence of language control deficits is not necessarily linked to deficits in EC, indicating that these two control domains may not entirely overlap.