Language and task switching in the bilingual brain: Bilinguals are staying, not switching, experts

Abstract

Bilinguals’ ability to control which language they speak and to switch between languages may rely on neurocognitive mechanisms shared with non-linguistic task switching. However, recent studies also reveal some limitations on the extent control mechanisms are shared across domains, introducing the possibility that some control mechanisms are unique to language. We investigated this hypothesis by directly comparing the neural correlates of task switching and language switching. Nineteen Spanish-English bilingual university students underwent a functional magnetic resonance imaging (fMRI) study employing a hybrid (event-related and blocked) design involving both color-shape switching and language switching paradigms. We compared the two switching tasks using within-subject voxel-wise t-tests for each of three trial types (single trials in single blocks, and stay and switch trials in mixed blocks). Comparing trial types to baseline in each task revealed widespread activation for single, stay, and switch trials in both color-shape and language switching. Direct comparisons of each task for each trial type revealed few differences between tasks on single and switch trials, but large task differences during stay trials, with more widespread activation for the non-linguistic than for the language task. Our results confirm previous suggestions of shared mechanisms of switching across domains, but also reveal bilinguals have greater efficiency for sustaining the inhibition of the non-target language than the non-target task when two responses are available. This efficiency of language control might arise from bilinguals’ need to control interference from the non-target language specifically when not switching languages, when speaking in single- or mixed-language contexts.

Bilingual Language Control in Perception versus Action: MEG Reveals Comprehension Control Mechanisms in Anterior Cingulate Cortex and Domain-General Control of Production in Dorsolateral Prefrontal Cortex

“…Importantly, the involvement of the dlPFC and the ACC replicates previous studies relating language-switching in production to the left (Hernandez et al, 2000;Rodriguez-Fornells et al, 2005;Wang et al, 2007) and right (Hernandez et al, 2001;Wang et al, 2007) dlPFC, and in comprehension to the left ACC . The language switch effects localized in the dlPFC in production also extended to category-switching, consistent with previous studies (De Baene et al, 2015) and the hypothesis that language control is a subdomain of general cognitive control (Craik and Bialystok, 2006;Garbin et al, 2010;Abutalebi et al, 2012).…”

“…Following previous studies that have found language-switching to recruit dorsolateral areas of the prefrontal cortex (dlPFC) in both hemispheres (Hernandez et al, 2000(Hernandez et al, , 2001RodriguezFornells et al, 2005;Wang et al, 2007), we analyzed Brodmann areas (BAs) 9, 10, and 46 bilaterally. Furthermore, because language-switching has been reported to involve the left ACC (Wang et al, 2007;Abutalebi et al, 2008, Crinion et al, 2006van Heuven et al, 2008), we also analyzed this area, including BA24, BA32, and BA33 in the analyses (MacDonald et al, 2000).…”

“…Following previous studies that have found language-switching to recruit dorsolateral areas of the prefrontal cortex (dlPFC) in both hemispheres (Hernandez et al, 2000(Hernandez et al, , 2001RodriguezFornells et al, 2005;Wang et al, 2007), we analyzed Brodmann areas (BAs) 9, 10, and 46 bilaterally. Furthermore, because language-switching has been reported to involve the left ACC (Wang et al, 2007;Abutalebi et al, 2008, Crinion et al, 2006van Heuven et al, 2008), we also analyzed this area, including BA24, BA32, and BA33 in the analyses (MacDonald et al, 2000). In addition, given that, in the left hemisphere, the prefrontal ROIs neighbored Broca's area, we also ran an analysis to assess whether linguistic switch effects would extend to the left inferior frontal gyrus (LIFG), including in this analysis BA44, BA45, and BA47 (ThompsonSchill et al, 1998;Poldrack et al, 1999;Wagner et al, 2000Wagner et al, , 2001BlancoElorrieta and Pylkkänen, 2015).…”

“…Prior language control research has mostly focused on production (Hernandez et al, 2001;Rodriguez-Fornells et al, 2005;Wang et al, 2007;Guo et al, 2011), leaving the neural underpinnings of language-switching in comprehension rather elusive (but see . In addition, the direct contrasts (i.e., same population tested on similar tasks involving language and general executive control) conducted in production have so far not reached a unanimous verdict regarding the degree of anatomical overlap between high-level cognitive control and bilingual language control: whereas some studies propose a nearly complete overlap between the two (De Baene et al, 2015;Weissberger et al, 2015), others suggest only partial overlap (Branzi et al, 2015) or mostly distinct networks (Abutalebi et al, 2008;Magezi et al, 2012).…”

“…In addition, the direct contrasts (i.e., same population tested on similar tasks involving language and general executive control) conducted in production have so far not reached a unanimous verdict regarding the degree of anatomical overlap between high-level cognitive control and bilingual language control: whereas some studies propose a nearly complete overlap between the two (De Baene et al, 2015;Weissberger et al, 2015), others suggest only partial overlap (Branzi et al, 2015) or mostly distinct networks (Abutalebi et al, 2008;Magezi et al, 2012). Here, we targeted both questions within the same design, addressing not only the neurobiological similarity of language-switching and non-language-switching, but also the commonality between language-switching in comprehension and production.…”