Short‐term language switching training tunes the neural correlates of cognitive control in bilingual language production

Abstract

The present study investigated how language switching experience would modulate the neural correlates of cognitive control involved in bilingual language production. A group of unbalanced Chinese-English bilinguals undertook an 8-day cued picture naming training during which they named pictures in either of their languages based on visually presented cues. Participants' brain activation was scanned before and after the training in the same task. Behavioral results revealed a significant training effect such that switch costs were reduced after training. fMRI results showed that after training, activation of brain areas associated with cognitive control including the anterior cingulated cortex and the caudate was reduced. Besides, the activation reduction in the left dorsal anterior cingulated cortex positively correlated with the reduction in switch costs in response time and this training effect could be transferred to untrained stimuli. These findings suggest that neural correlates of cognitive control, especially that of the conflict monitoring process, in bilingual language production could be modulated by short-term language switching training. Hum Brain Mapp 38:5859-5870, 2017. © 2017 Wiley Periodicals, Inc.

Ecological Validity in Bilingualism Research and the Bilingual Advantage

“…Neurobiological investigations using these paradigms have additionally found that language switching as prompted by a cue elicits engagement of executive control regions, mainly the prefrontal cortex [7][8][9][17][18][19], the pre-supplementary motor area/anterior cingulate cortex (pre-SMA/ ACC) [7,8,[19][20][21][22][23][24], and the left caudate nucleus [23][24][25][26][27] (see meta-analysis in [18] and reviews in [26][27][28][29][30]). The literature stemming from this paradigm has proven highly consistent, with widely replicated results across the world in multilingual individuals with many different linguistic backgrounds [7][8][9][10][11][12][13][14][15][16][17][20][21][22][23][24][25]. As a result, this work has formed the main empirical basis for models of bilingual language switching.…”

“…According to this hypothesis, bilingual individuals, as a mere consequence of being bilingual develop an improved cognitive control system. Because the neural underpinnings of language control and general domain executive control overlap to some extent [8][9][10]25,[64][65][66][67]; cf. [11,68], this enhancement in language control mechanisms is proposed to generalize to nonlinguistic tasks, resulting in an advantage in many tasks requiring selective attention and inhibition (for comprehensive reviews see [69][70][71][72]).…”

“…Relevant empirical evidence comes from recent studies showing a direct relation between individuals' language switching background and their performance during task switching [92][93][94][95][96][97][98]. A recent study [92] compared the performance of monolinguals, bilinguals who switch languages often, and bilinguals who do not switch often in a task-switching paradigm.…”

“…Methodologically, these questions are not easy to answer as it is highly nontrivial to find reliable ways to elicit language switches on demand in the laboratory. To accomplish this, researchers have commonly devised rather artificial switching paradigms, in which bilingual individuals are asked to name a picture or a number in one or another language as prompted by an external cue displayed on the screen [4][5][6][7][8][9][10][11][12][13][14]. The relation between the external cue and its associated language has been arbitrary in these designs: a color or a symbol is selected randomly, and participants are asked to learn the association between this cue and the language it represents.…”

“…The relation between the external cue and its associated language has been arbitrary in these designs: a color or a symbol is selected randomly, and participants are asked to learn the association between this cue and the language it represents. Studies using such paradigms have consistently demonstrated longer reaction times and higher error rates for trials in which participants must switch languages than for trials involving no switching [4][5][6][8][9][10][11][12][13] (for a review see [15,16]). This has led to the conclusion that language switching is behaviorally effortful [i.e., there are switch costs (see Glossary)].…”