Neurohemodynamic correlates of antonym generation in bilinguals

Abstract

Objectives: Bilingualism and multilingualism are the norms of the society. The study was undertaken to assess the neural systems of language in bilinguals by means of antonym generation in Tamil to Tamil (TT) language, English to English (EE) language, and code-switching between Tamil to English (TE) using functional magnetic resonance imaging (fMRI). Methods: Proficient 16 Tamil-native speakers from rural Tamil Nadu, South India, participated in the study. Tamil (L1) was the first language and English (L2) was the second language in Cognitive Neuro Centre, NIMHANS. Single assessment design was used. Antonym generation task was used for the study with fMRI. Results: TT task uniquely activated right frontotemporal gyrus along with left caudate and lentiform nucleus. TE activated left parahippocampal and right cerebellar tonsil. Using conjunction analysis, it was found that during TT task, robust activations were present in multiple bilateral prefrontal areas, premotor area, bilateral insula, bilateral lingual gyrus, claustrum, and bilateral cerebellum. Common areas for TT and EE are precentral gyrus, cingulate gyrus, and right dentate. However, EE and TE activated bilateral parietal gyrus, cingulate gyrus, bilateral fusiform gyrus, angular gyrus bilateral thalamus, bilateral culmen, and right inferior semilunar lobule on the blood oxygenation level dependent of fMRI. Conclusions: The nature of the language produces unique neural circuits. The language processing in the brain requires executive processes and cognitive controls. The study has implications for cognitive network pattern analysis which could possibly aid in rehabilitation.