Exploring the effect of Relative Language Distance on Bilingual Brain Structure: a cross-sectional VBM study

It is known that bilinguals perpetual need for language control influences their brain structure in significant ways. But bilinguals language control needs are themselves influenced by key dimensions of the bilingual experience - variation in the age of bilingualism-onset, relative language proficiency, exposure and immersion has indeed been shown to have differential effects on bilingual neurostructural profiles. An under-studied dimension of bilingualism that could also generate differing bilingual language control needs is the extent of similarity between bilinguals language pairs, referred to in the present study as Relative Language Distance (RLD). The goal of the present study was to explore whether the experience of managing \"close\" and \"distant\" languages has any impact at all on bilingual brain structure. To this end, exploratory morphometric analysis of grey matter volumes was carried out on three groups, all very similar in their bilingual profiles except for the factor of RLD - high-distance Cantonese-English (hd-CE), intermediate distance Hindi-English (id-HE) and low-distance Dutch-English (ld-DE) speakers. The results after controlling for contribution of other bilingual dimensions revealed significant bilateral putaminal volume differences between the groups that varied along the relative language distance gradient in the pattern of CE>HE>DE. This might be attributable to the differing articulatory control needs that variation in L1-L2 RLD generates. The present study reveals how the dimension of Relative Language Distance could impact bilingual brain structure.