L2 speech perception in noise: An fMRI study of advanced Spanish learners

This experiment examined the neural correlates of second language (L2) speech perception in noise in advanced Spanish students. Participants completed a speech perception task in quiet and noise in their first language (L1 = English) and L2 during fMRI. Behavioral tests of L2 Spanish sentence recognition confirmed that advanced learners of Spanish can recognize sentences in quiet and in noise with an average of 85.45% and 74.43% accuracy, respectively. While listening to degraded sentences in the L2, both auditory and executive processing regions (specifically those of attention) were activated. While listening to L2 sentences in noise, learners focused on decoding the speech signal at the perceptual level, indicating a bottom-up processing strategy relying heavily on the signal's phonetic detail. During the processing of L1 in noise there was only significant activation in executive processing regions like the cingulate cortex and a region linked to lexical-semantic access (LIFG). In this case, participants appear to use a top-down strategy for sentence recognition, relying on lexical resources using a holistic strategy for perception. These findings suggest that L2 learners use fundamentally different perceptual strategies and neural circuits for understanding speech in noise in their L1 and L2.