Auditory spatial attention through transcranial direct current stimulation in bilinguals

Abstract

Bilingualism enhances cognitive flexibility, executive functioning, and attention, but can lead to challenges like smaller vocabulary and reduced verbal fluency. Bilinguals often struggle with speech recognition in noisy environments, particularly in their non-native language. Neuroplastic adaptations from bilingualism alter brain anatomy, though the extent and implications of these changes are still not fully understood. The aim of the study was to investigate the effects of anodal transcranial direct current stimulation (tDCS) on language comprehension focusing on native Urdu (L1) and second language English (L2) in bilingual individuals, considering proficiency levels. Fifty healthy subjects participated in this randomized, single-blinded, and single session study involving an Active and Control groups. Stimuli consisted of 88 sentences presented in 2 blocks the subjects performed three sessions including practice session of 2 mins followed by pre-tDCS session of 7 minutes,20 minutes of offline active tDCS /no stimulation and 7 minutes of post tDCS session, with performance evaluated based on key words identified from target sentences. A two-way repeated measures ANOVA was used for the analysis. The analysis of variance (ANOVA) results comparing pre- and post-intervention scores revealed significant improvements in both the Active and Control groups. We found that tDCS enhanced auditory spatial attention with greater impact on the dominant language, especially among those with higher proficiency level (p<0.05). Control group also showed improvements in both languages. The cross-linguistic effects observed indicate that tDCS may facilitate language transfer between bilinguals. These findings suggest pathways for further investigation of tDCS in language learning and rehabilitation, particularly in multilingual environments.