Cross-language interaction during sequential anomia treatment in three languages: Evidence from a trilingual person with aphasia.

Language rehabilitation research has reported mixed evidence in bilinguals with aphasia suggesting that therapy can benefit the treated language alone or additionally result in cross-language generalization to the untreated language, while cross-language interference effects are less common. However, treatment effects in multilinguals with aphasia (MWA) have been less frequently investigated, and examining cross-language interactions during therapy may help to better understand their treatment response in each language. This study reports on P1, a trilingual person with severe aphasia with extensive damage to cortical language regions and the basal ganglia, who received sequential semantic-based treatment for anomia in her L3 French, L1 Spanish and L2 English. Overall, significant treatment gains in the treated language were restricted to her L3 French, the weakest language, while her treatment response was limited across languages likely due to severe language impairment and extensive damage to the language processing network. Cross-language generalization effects were absent and P1 showed cross-language interference in her L2 English during treatment in her L3 French. Cross-language intrusions were observed between languages, more frequently in her L2 English (the least available language in treatment) than in her L1 Spanish (the strongest language). The absence of cross-language generalization and presence of cross-language interference in P1 were likely due to damage in the basal ganglia and executive deficits reflecting damage to the language control network. Severe language processing and language control impairments can hinder the balance between activation and inhibition mechanisms necessary to support response to language treatment in MWA.