Neural bases of listening to speech in noise

Ubiquitous speech processing involves listening to speech in ecological environments where noise is often present. The current study investigates the neural mechanisms involved in perceiving speech in noise using a sparse sampling fMRI method. Subjects were asked to match auditorily presented words with picture choices. The auditory stimuli were either presented in quiet or embedded in multi-talker babble noise without the presence of scanner noise in either condition. Behaviorally, it was found that subjects were slower and less accurate in identifying words presented in noise. Comparison of hemodynamic responses associated with listening to the two types of stimuli revealed increased activation in left prefrontal, inferior frontal, anterior insular, and superior temporal regions when subjects listened to speech in noise. These results confirm the importance of the lateral auditory cortex in complex auditory processing and suggest that the prefrontal cortex is likely to be prominently engaged in subvocal rehearsal when noise is affecting the integrity of the speech signal.