Neural mechanisms of long-term sensorimotor adaptation in L1 and L2 speech motor control systems

This study compared the neural mechanisms of long-term sensorimotor adaptation in English first language (L1) and second language (L2) speakers using a sustained perturbation paradigm. Behavioral and event-related potential findings demonstrated significant sensorimotor adaptation effects across all experimental phases for L1 speakers but only in the late adaptation phase for L2 speakers, suggesting their efficiency differences in using auditory feedback for the long-term update of feedforward motor commands. This assumption was further supported by source localization results that L1 and L2 speakers recruited similar network for sensorimotor adaptation but L2 speakers activated greater extent. We also identified language-specific changes in theta-gamma phase coherence as speakers adapted to the task, revealing that such coherence may be an indicator of the stability of speech sounds' sensorimotor representations. Altogether, our findings have implications for understanding how the persistent problem of inaccurate speech relates to L2 speech motor system.