Cross-linguistic perspectives on morphosyntactic impairment in Russian-Hebrew bilingual aphasia: insights for representational and processing frameworks

Background Morphosyntactic impairments in individuals with agrammatic aphasia, especially in noncanonical structures, have been linked either to representational deficits, reflected in impaired syntactic knowledge, to processing limitations involving reduced verbal working memory (WM), or to their interaction. How these factors operate across structurally distinct languages remains unclear. Examining bilingual individuals with aphasia (biPWAs) who speak typologically different languages may therefore shed light on whether morphosyntactic impairments display shared or divergent patterns across the two languages.Objectives This study examines morphosyntactic comprehension and production in L1-Russian- and L2-Hebrew-speaking biPWAs, testing whether impairments are language-specific or shared, and whether verbal WM is linked to morphosyntactic deficits in each language, with visuospatial STM serving as a control.Methods Twenty chronic-stage biPWAs and twenty matched bilingual controls completed the Bilingual Aphasia Test (BAT) Morphosyntactic Comprehension and Sentence Repetition subtests, and narrative production tasks in both languages. Verbal STM and WM were assessed using Forward Digit Span and language-specific listening span tasks, respectively; visuospatial STM was measured via the Corsi Block Tapping task.Results BiPWAs showed significant morphosyntactic deficits in comprehension and production, most pronounced in L2-Hebrew. Comprehension difficulties were marked for sentences with negation, including both active and passive forms in L1-Russian and mainly passive forms in L2-Hebrew. Repetition deficits were largest for object relatives in L1-Russian and for both subject and object relatives in L2-Hebrew. Narrative production featured a lower proportion of complex sentences overall. Structural equation analysis revealed robust bidirectional links between verbal WM and morphosyntactic performance in L1-Russian, with weaker and statistically unreliable associations in L2-Hebrew. Partial-correlation network analyses confirmed that verbal, but not visuospatial STM, was consistently connected to morphosyntactic measures across languages.Conclusions The systematic impairment of movement-derived structures across both languages, together with the strong links between reduced verbal WM and complex sentence processing, indicates that morphosyntactic deficits in biPWAs arise from an interaction of representational damage and verbal WM limitations. Language-specific vulnerabilities and domain-general processing constraints jointly shape morphosyntactic outcomes in bilingual aphasia.