Cognitive and Neural Control in Bilingual Language Processing

Bilingual individuals seem to easily speak in just one language, and switch back and forth between languages, suggesting they have powerful mechanisms for controlling activation of their two languages. A prominent theory suggests that cognitive control, and specifically inhibition of the non-target language, enables successful switching. We used behavioral and neuroimaging methods to study Spanish-English bilinguals to determine: 1) if college-aged bilinguals show an advantage in general task-switching ability relative to monolinguals given bilinguals’ extensive practice with language switching; 2) if cognitive control regions are recruited in bilingual language comprehension, and 3) if an aging deficit in inhibitory control affects older bilinguals’ (age 65+) ability to switch languages. In Study 1 (n = 80 per group; Stasenko et al., 2017) bilinguals exhibited more efficient task-switching, but only when participants had longer preparation time, and the advantage dissipated quickly. These findings suggest that although bilingualism improves the efficiency of task switching, this advantage might be more related to preparing to switch than to switching per se. In Study 2 (n = 24; Stasenko et al., 2020), bilinguals recruited fronto-parietal brain regions (i.e., right frontal inferior gyrus, bilateral middle frontal gyrus, and left supramarginal gyrus) when switching relative to not switching languages even in silent reading of mixed language paragraphs (without producing any switches in their speech). These results suggest that although reading comprehension seems to be passive, it recruits brain regions known to support cognitive control, possibly reflecting a modality-general switch mechanism. Study 3 (ns = 48 and 25; Stasenko et al., submitted) revealed a reversal of language dominance in mixed-language testing blocks, and a transfer of inhibition from a repeated set of items to a new set of items (that was introduced halfway through the task). Both effects were found only in younger but not in older bilinguals. Overall, these findings support the role of domain-general cognitive control and inhibition as an important mechanism in bilingual language control that spans across production and comprehension and exhibits decline in healthy aging

Cognitive and Neural Control in Bilingual Language Processing

Bilingual individuals seem to easily speak in just one language, and switch back and forth between languages, suggesting they have powerful mechanisms for controlling activation of their two languages. A prominent theory suggests that cognitive control, and specifically inhibition of the non-target language, enables successful switching. We used behavioral and neuroimaging methods to study Spanish-English bilinguals to determine: 1) if college-aged bilinguals show an advantage in general task-switching ability relative to monolinguals given bilinguals’ extensive practice with language switching; 2) if cognitive control regions are recruited in bilingual language comprehension, and 3) if an aging deficit in inhibitory control affects older bilinguals’ (age 65+) ability to switch languages. In Study 1 (n = 80 per group; Stasenko et al., 2017) bilinguals exhibited more efficient task-switching, but only when participants had longer preparation time, and the advantage dissipated quickly. These findings suggest that although bilingualism improves the efficiency of task switching, this advantage might be more related to preparing to switch than to switching per se. In Study 2 (n = 24; Stasenko et al., 2020), bilinguals recruited fronto-parietal brain regions (i.e., right frontal inferior gyrus, bilateral middle frontal gyrus, and left supramarginal gyrus) when switching relative to not switching languages even in silent reading of mixed language paragraphs (without producing any switches in their speech). These results suggest that although reading comprehension seems to be passive, it recruits brain regions known to support cognitive control, possibly reflecting a modality-general switch mechanism. Study 3 (ns = 48 and 25; Stasenko et al., submitted) revealed a reversal of language dominance in mixed-language testing blocks, and a transfer of inhibition from a repeated set of items to a new set of items (that was introduced halfway through the task). Both effects were found only in younger but not in older bilinguals. Overall, these findings support the role of domain-general cognitive control and inhibition as an important mechanism in bilingual language control that spans across production and comprehension and exhibits decline in healthy aging

MINT in Bilingual Alzheimer's Disease

Gollan et al (2023) - Neuropsycholog

A relative bilingual advantage in switching with preparation: Nuanced explorations of the proposed association between bilingualism and task switching.

Bilingual language switching may increase general switching efficiency, but the evidence on this question is mixed. We hypothesized that group differences in switching might be stronger at a long cue-target interval (CTI), which may better tap general switching abilities (Yehene & Meiran, 2007). Eighty Spanish-English bilinguals and 80 monolinguals completed a color-shape switching task, and an analogous language-switching task, varying CTI (short vs. long) in both tasks. With longer preparation time (long CTI), bilinguals exhibited significantly smaller task-switching costs than monolinguals, but only in the first half of trials. Group differences diminished with practice, though practice benefitted RTs on short CTI trials more than long, and bilinguals committed fewer errors with practice especially at short CTI. Groups did not differ in mixing costs; however, across CTIs and tasks, bilinguals and monolinguals alike, exhibited robust correlations between mixing costs, but not between switching costs. These results confirm an association between bilingualism and switching efficiency that may be magnified with manipulations that target general switching ability (or could reflect better ability to take advantage of preparation time). However, practice effects observed within experimental paradigms, and between task correlations in costs, may reflect cognitive mechanisms specific to laboratory tasks much more than associations with general switching ability and executive control mechanisms-for which more reliable and valid measures can hopefully be developed in future work. (PsycINFO Database Recor

Cognitive control regions are recruited in bilinguals silent reading of mixed-language paragraphs.

When switching languages, bilinguals recruit a language control network that overlaps with brain regions known to support general cognitive control, but it is unclear whether these same regions are recruited in passive comprehension of language switches. Using fMRI with a blocked design, 24 Spanish-English bilinguals silently read 36 paragraphs in which the default language was Spanish or English, and that had either (1) no switches, (2) function word switches or (3) content word switches. Relative to no switches, function switches activated the right IFG, bilateral MFG, and left IPL/SMG. In contrast, switching on content words produced limited neural switching costs observed only in the left IFG. Switching into the dominant language was more costly in the right SMG than switching into the nondominant language, and neural switching costs were correlated with switching costs in the dominant language in cued picture-naming. Seemingly passive reading comprehension involves brain regions known to support cognitive control in active switching during production, possibly reflecting the operation of a modality-general switch mechanism

Bilingual language intrusions and other speech errors in Alzheimer’s disease

The current study investigated how Alzheimer's disease (AD) affects production of speech errors in reading-aloud. Twelve Spanish-English bilinguals with AD and 19 matched controls read-aloud 8 paragraphs in four conditions (a) English-only, (b) Spanish-only, (c) English-mixed (mostly English with 6 Spanish words), and (d) Spanish-mixed (mostly Spanish with 6 English words). Reading elicited language intrusions (e.g., saying la instead of the), and several types of within-language errors (e.g., saying their instead of the). Patients produced more intrusions (and self-corrected less often) than controls, particularly when reading non-dominant language paragraphs with switches into the dominant language. Patients also produced more within-language errors than controls, but differences between groups for these were not consistently larger with dominant versus non-dominant language targets. These results illustrate the potential utility of speech errors for diagnosis of AD, suggest a variety of linguistic and executive control impairments in AD, and reveal multiple cognitive mechanisms needed to mix languages fluently. The observed pattern of deficits, and unique sensitivity of intrusions to AD in bilinguals, suggests intact ability to select a default language with contextual support, to rapidly translate and switch languages in production of connected speech, but impaired ability to monitor language membership while regulating inhibitory control