Sustained and transient language control in the bilingual brain.

Bilingual speakers must have effective neural mechanisms to control and manage their two languages, but it is unknown whether bilingual language control includes different control components. Using mixed blocked and event-related designs, the present study explored the sustained and transient neural control of two languages during language processing. 15 Chinese-English bilingual speakers were scanned when they performed language switching tasks. The results showed that, compared to the single language condition, sustained bilingual control (mixed language condition) induced activation in the bilateral inferior frontal, middle prefrontal and frontal gyri (BA 45/46). In contrast, relative to the no switch condition, transient bilingual control (language switching condition) activated the left inferior parietal lobule (BA 2/40), superior parietal lobule (BA 7), and middle frontal gyrus (BA 11/46). Importantly, the right superior parietal activity correlated with the magnitude of the mixing cost, and the left inferior and superior parietal activity covaried with the magnitude of the asymmetric switching costs. These results suggest that sustained and transient language control induced differential lateral activation patterns, and that sustained and transient activities in the human brain modulate the behavioral costs during switching-related language control.