Neural bases of language switching in high and early proficient bilinguals

► Language switching in early bilinguals is related to the left caudate and pre-SMA. ► Brain areas involved in language switching in early and late bilinguals are different. ► The left caudate is specifically related to the inhibition of the dominant language. ► The pre-SMA/ACC participates in backward switching in early bilinguals. The left inferior frontal cortex, the caudate and the anterior cingulate have been proposed as the neural origin of language switching, but most of the studies were conducted in low proficient bilinguals. In the present study, we investigated brain areas involved in language switching in a sample of 19 early, high-proficient Spanish–Catalan bilinguals using a picture naming task that allowed contrasting switch and non-switch trials. Compared to the non-switching condition, language switching elicited greater activation in the head of the left caudate and the pre-SMA/ACC. When the direction of the switching was considered, the left caudate was more associated with forward switching and the pre-SMA/ACC with backward switching. The discussion is focused on the relevance of these brain structures in language control in early, high-proficient bilinguals, and the comparison with previous results in late bilinguals.