Control mechanisms in bilingual language production: Neural evidence from language switching studies

Abstract

A key question in bilingual language production research is how bilingual individuals control the use of their two languages. The psycholinguistic literature concerning language control is unresolved. It is a matter of controversy whether (a) issues to do with control are central to understanding bilingual language processing; and (b) if they are, what is the site or sites of control; and (c) whether language control in bilinguals relies upon inhibitory mechanisms.

One way to deepen our understanding of language control is to consider the implications from research on functional neuroimaging. In the present paper, we illustrate that neuroimaging research shows that bilinguals engage cognitive control networks for achieving tasks such as language switching. The neural evidence points to multiple neural regions of control that may rely upon an inhibitory mechanism. These ‘brain data’ may, in turn, stimulate the development of neurocognitive accounts of bilingual language processing.

Acknowledgements

We thank the Wellcome Trust for support to David Green.

Notes

¹At a first view, it may seem counterintuitive that a lesion to the left prefrontal cortex may lead to unintentional language switching, since as shown above, this region is involved in language switching. However, as outlined by Abutalebi et al. (2001), Mariën et al. (2005) and Abutalebi and Green (2007), the prefrontal cortex is part of a larger network underlying language control in bilinguals. As such, a lesion may interfere with control of languages rather than with language switching per se producing two distinctive features of deficits: on the one hand, impaired control may lead to pathological and unintentional switching; and on the other, it may lead to pathological fixation on a given language (i.e., in the sense that the control system is unable to activate a given language).

²It is worth mentioning that the pars triangularis of the left prefrontal cortex was traditionally associated with language production, but in recent years functional neuroimaging studies have also revealed that the functions pertaining to the pars triangularis and surrounding areas are not only confined to language processing. Indeed, it is engaged also in other domains requiring cognitive control (Koechlin et al., 2003), executive control over hierarchically structured action plans (Koechlin & Jubault, 2006) and working memory (Paulesu, Frith, & Frackowiak, 1993; Smith & Jonides, 1999).