The cognitive function of the human cerebellum could be characterized as enigmatic. However, researchers have attempted to detail the comprehensive role of the cerebellum in several cognitive processes in recent years. Here, using functional magnetic resonance imaging (fMRI) and transcranial direct current stimulation (tDCS), we revealed different functions of bilateral cerebellar lobules in bilingual language production. Specifically, brain activation showed the bilateral posterolateral cerebellum was associated with bilingual language control, and an effective connectivity analysis built brain networks for the interaction between the cerebellum and the cerebral cortex. Furthermore, anodal tDCS over the right cerebellum significantly optimizes language control performance in bilinguals. Together, these results reveal a precise asymmetrical functional distribution of the cerebellum in bilingual language production, suggesting that the right cerebellum is more involved in language control. In contrast, its left counterpart undertakes a computational role in cognitive control function by connecting with more prefrontal, parietal, subcortical brain areas.

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How speaking two languages affects executive functions has been a longstanding debate and the mechanisms underlying the observed cognitive advantages of bilingualism remain unspecified. Here, using multivariate pattern classification methods, we decoded spatial patterns of neural signals associated with Flanker task performance in mono-dialectal and bi-dialectal speakers of Chinese. While univariate approach to even-related potentials (ERPs) showed no between-group difference, decoding accuracy of ERPs was reduced in bidialectal as compared to mono-dialectal speakers in both congruent-neutral and incongruent-neutral classifications. There was no effect of bidialectalism, however, on decoding accuracy of alpha-band oscillations, an electrophysiological index implicated in inhibition. Behavioural data analysed using the Drift Diffusion Model (DDM) showed facilitating effects of bidialectalism on non-decision times but no effect on drift rates. These findings demonstrate that using two dialects on a daily basis enhances general attentional deployment rather than affecting specific component of executive functions such as inhibitory control. Given that the two dialects of Chinese differed almost exclusively in phonology, the bidialectalism effect was most likely motivated by resolving phonological competition at lexical processing level. | INTRODUCTIONResearch has shown that bilingual individuals automatically activate both languages even when functioning in a single-language language context (e.g., Jacobs et al., 2016;Thierry & Wu, 2007). The target language is selected by inhibiting lexical representations of the non-target language (Green, 1998;Green & Abutalebi, 2013). This unique language experience of bilinguals has been associated with enhanced domain-general cognitive abilities such as executive functions (Bialystok, 2017(Bialystok, , 2021Bialystok et al., 2012). Executive function is an umbrella term for higher-order cognitive skills that include, but not limited to, suppression of interference from irrelevant Abbreviations: DDM, drift diffusion model; ECOC, error-correcting output codes; EEG, electroencephalography; ERP, event-related potentials; HDDM, hierarchical drift diffusion model; MCMC, Markov chain Monte Carlo; MVPA, multivariate pattern analysis; SVM, support vector machine.