Subcortical Lesions Impact Confrontation Naming in Bilinguals with Later Age of Acquisition

Abstract

Abstract Objective Multilinguals show greater subcortical activation during language tasks than monolinguals. Among multilinguals, prior studies found later age of acquisition (AoA) of a second language in association with more diffuse, non-traditional language representation. While such findings have clear clinical implications, little research has examined relationships among linguistic history, neuroanatomical integrity, and language skills in a clinical population. This study examined relationships between subcortical lesions and confrontation naming in strong bilinguals who acquired English (L2) later in life compared to those with earlier AoA. Participants and Method Forty-two bilinguals with Spanish as a first language (English L2) were selected from a database of veterans referred for clinical neuropsychological evaluation (M Age = 64 years; M Education = 12 years; 93% men). They reported strong bilingualism after L2 acquisition (M AoA = 10 years), with current English preference. Twenty-nine had neuroimaging, which was coded on a 4-point ordinal scale for lesion burden in white matter and striatum. Moderation models were tested for interaction between AoA and subcortical lesions in bilinguals using different L2 naming outcomes, controlling for age, education, occupation, and English fluency (i.e., Test of Premorbid Functioning). Results Moderation showed significant interaction of AoA with striatal lesion burden for scores on all naming tests, with a similar but less robust relationship between white matter lesions and naming outcomes. Graphical analysis revealed subcortical lesions had a negative impact on naming scores in those with later L2 AoA. Conclusions Results suggest “atypical” subcortical involvement in naming is more likely for bilinguals who acquired L2 later. While clinicians typically associate impaired naming with temporal lobe dysfunction, findings suggest subcortical dysfunction should be considered among bilinguals with later L2 AoA.