Abstract
The present functional magnetic resonance imaging (fMRI) study investigated influences of language contexts on inhibitory control and the underlying neural processes. Thirty Cantonese–Mandarin–English trilingual speakers, who were highly proficient in Cantonese (L1) and Mandarin (L2), and moderately proficient in English (L3), performed a picture-naming task in three dual-language contexts (L1-L2, L2-L3, and L1-L3). After each of the three naming tasks, participants performed a flanker task, measuring contextual effects on the inhibitory control system. Behavioral results showed a typical flanker effect in the L2-L3 and L1-L3 condition, but not in the L1-L2 condition, which indicates contextual facilitation on inhibitory control performance by the L1-L2 context. Whole brain analysis of the fMRI data acquired during the flanker tasks showed more neural activations in the right prefrontal cortex and subcortical areas in the L2-L3 and L1-L3 condition on one hand as compared to the L1-L2 condition on the other hand, suggesting greater involvement of the cognitive control areas when participants were performing the flanker task in L2-L3 and L1-L3 contexts. Effective connectivity analyses displayed a cortical-subcortical-cerebellar circuitry for inhibitory control in the trilinguals. However, contrary to the right-lateralized network in the L1-L2 condition, functional networks for inhibitory control in the L2-L3 and L1-L3 condition are less integrated and more left-lateralized. These findings provide a novel perspective for investigating the interaction between bilingualism (multilingualism) and inhibitory control by demonstrating instant behavioral effects and neural plasticity as a function of changes in global language contexts.
Highlights
Bilingualism is a form of “mental juggler” (Kroll and Bialystok, 2013), as speaking one language often involves simultaneous access to the non-target language in the brain (Dijkstra and Van Heuven, 1998; Green, 1998; Bialystok, 2007; Thierry and Wu, 2007; Wu and Thierry, 2010, 2017; De Groot, 2012)
In an functional magnetic resonance imaging (fMRI) study on German– Italian–English trilinguals, Abutalebi et al (2013a,b) showed that language-switching directions influenced brain activation levels in the caudate nuclei, while activation levels of the supplementary motor area (SMA)/anterior cingulate cortex (ACC) did not vary as the function of language proficiency, which suggests a domain-general role for SMA/ACC in control tasks
To reconcile discrepancies in previous studies, the present study explores the effect of language contexts on the neurocognitive mechanism of inhibitory control in a group of Cantonese–Mandarin–English trilinguals, who were highly proficient in Cantonese (L1)1 and Mandarin (L2), and moderate proficient in English (L3)
Summary
Bilingualism is a form of “mental juggler” (Kroll and Bialystok, 2013), as speaking one language often involves simultaneous access to the non-target language in the brain (Dijkstra and Van Heuven, 1998; Green, 1998; Bialystok, 2007; Thierry and Wu, 2007; Wu and Thierry, 2010, 2017; De Groot, 2012). Abutalebi and Green’s (2007) hypothesis is that this neural network is dedicated to the selection and temporal sequencing of language representations during bilingual word production, and the pipeline works in the following order: The left basal-ganglia and ACC modulate the neural activity levels in the left prefrontal cortex, which influences neural activity in the inferior parietal cortex Each of these areas has implications in distinct cognitive processes: The prefrontal cortex inhibits the non-target language and corrects errors; the ACC monitors conflicts and detects errors; the basal ganglia, especially the caudate nuclei, supervises the language selection and lexical access; the inferior parietal lobule, as a key region for working memory, serves a goal maintenance function. How these areas are connected with one another as part of the control network remains unclear
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