Cortical contributions to the auditory brainstem response revealed by MEG

Abstract: The auditory brainstem response (ABR) to complex periodic sounds, such as those found in speech and music, is used to study the subcortical auditory system and as a clinical biomarker for a variety of problems and conditions. Because ABRs are uniquely suited to studying fine temporal encoding in the intact human auditory system, an accumulation of ABR-based results now supports some of our general understanding of the auditory system. However, while ABRs are assumed to originate in the brainstem (as the name suggests), their neural origins are unclear. Using magnetoencephalography, we investigated the neural origins of the ABR’s frequency following response (FFR) to periodic sound components for the first time. We observed a strong, right-asymmetric contribution to the ABR from the auditory cortex at the fundamental frequency of the stimulus, in addition to signal from brainstem nuclei. This finding is highly relevant for our understanding of plasticity and pathology in the auditory system as well as higher-level cognition such as speech and music processing: it suggests that previous interpretations of the ABR may need re-examination using methods that allow for source separation.

Emily Coffey is a graduate student and Doctoral Candidate in Zatorre Lab, MNI, McGill University.