Alpha-Band Brain Activity Shapes Online Perceptual Learning of Concurrent Speech Differentially in Musicians vs. Nonmusicians

Abstract

Plasticity from auditory experience shapes the brain's encoding and perception of sound. Though stronger neural entrainment (i.e., brain-to-acoustic synchronization) aids speech perception, underlying oscillatory activity may uniquely interact with long-term auditory experiences (i.e., music training) and short-term plasticity during concurrent speech perception. Here, we explored oscillatory activity during rapid auditory perceptual learning of concurrent speech sounds in normal-hearing young adults who differed in their amount of self-reported music training (defined as “musicians” and “nonmusicians”). Participants learned to identify double-vowel mixtures during ~45 min training sessions with concurrent high-density EEG recordings. We analyzed alpha-band power (7–12 Hz) following a rhythmic speech-stimulus train (~9 Hz) preceding behavioral identification to determine whether increased (brain-to-speech entrainment) or decreased alpha activity (alpha-band suppression) corresponded with task success. Source and directed functional connectivity analyses of EEG data probed whether behavior was driven by group differences in auditory-motor coupling. Both groups improved in behavioral identification with training. Listeners' alpha-band power prior to target speech predicted behavioral identification performance; surprisingly, stronger alpha oscillations were observed preceding incorrect compared to correct trial responses. We also found stark hemispheric biases in auditory-motor coupling, with greater auditory-motor connectivity in right compared to left hemisphere for musicians (R > L) but not in nonmusicians (R = L). Stronger alpha activity preceding incorrect behavioral responses supports the notion that alpha-band (~10 Hz) suppression is an important modulator of trial-by-trial success in perceptual processing. Our findings suggest that neural oscillations and auditory-motor connectivity interact with music training to impact speech perception.