Beyond bilingualism: multilingual experience correlates with caudate volume
The multilingual brain implements mechanisms that serve to select the appropriate language as a function of the communicative environment. Engaging these mechanisms on a regular basis appears to have consequences for brain structure and function. Studies have implicated the caudate nuclei as important nodes in polyglot language control processes, and have also shown structural differences in the caudate nuclei in bilingual compared to monolingual populations. However, the majority of published work has focused on the categorical differences between monolingual and bilingual individuals, and little is known about whether these findings extend to multilingual individuals, who have even greater language control demands. In the present paper, we present an analysis of the volume and morphology of the caudate nuclei, putamen, pallidum and thalami in 75 multilingual individuals who speak three or more languages. Volumetric analyses revealed a significant relationship between multilingual experience and right caudate volume, as well as a marginally significant relationship with left caudate volume. Vertex-wise analyses revealed a significant enlargement of dorsal and anterior portions of the left caudate nucleus, known to have connectivity with executive brain regions, as a function of multilingual expertise. These results suggest that multilingual expertise might exercise a continuous impact on brain structure, and that as additional languages beyond a second are acquired, the additional demands for linguistic and cognitive control result in modifications to brain structures associated with language management processes.
KeywordsCaudate nucleus Putamen Basal ganglia Multilingualism Bilingualism Language Volumetry Morphometry
The authors are grateful to three anonymous reviewers whose helpful suggestions allowed us to substantially improve the manuscript. We also wish to express our gratitude to the staff at the Brain and Behaviour Lab at the University of Geneva and at the Lausanne University Medical Centre who supported the data acquisition.
This work was supported by the Swiss National Science Foundation Grants PP00P3_133701 and PP00P3_163756 awarded to NG.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed were in accordance with the standards of the local research ethics committees of the University Hospitals of Geneva and Lausanne, and with the 1964 Helsinki declaration and its later amendments.
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