The Integrated Auditory System: Communication and Cognition through the Lens of Musical ExpertisePublic Deposited
When we speak, we communicate not only with the words we choose, but also with the patterns of sound we create. As auditory experts, musicians are especially adept at making sense of sound, and accumulating research reveals that this extends to their processing of speech and other communication signals. Much research to date has focused on comparisons of musicians with their non-musician peers, however cross-sectional studies cannot differentiate the causal effects of training from pre-existing differences. Further, the simple dichotomy of musician vs. non-musician ignores the myriad facets of musical expertise. The first part of this dissertation extends previous observations of a “musician signature” of neural and perceptual expertise in two important directions: 1) longitudinal assessment of the impact of music training on children’s auditory skills and 2) cross-sectional comparisons of different types of musicians, specifically drummers/percussionists and vocalists. The longitudinal study reveals improvements in speech-in-noise perception and neural speech processing after two years of group music class. The cross-sectional investigations reveal unique neural signatures of vocalists and percussionists, with corresponding enhancements in the neural encoding of spectral and temporal features of speech. Further, the rhythm experts (drummers/percussionists) show advantages in speech-in-noise perception and inhibitory control. The second part of the dissertation builds from these findings to focus on rhythm, examining how distinct aspects of rhythmic expertise contribute to rhythm discrimination, speech-in-noise perception and attention-related skills. Results reveal that while multiple rhythmic sub-skills (including beat- and sequence-based tasks) contribute to the discrimination of musical rhythms, it is only sequence-based tasks that contribute to the perception of speech in noise. In contrast, inhibitory control is strongly correlated with the ability to synchronize with a simple beat, and with a neural index of beat alignment. Taken together, these outcomes suggest that multiple timing mechanisms are strengthened in rhythmic experts, but engaged to differing degrees based on perceptual and cognitive demands. These results are interpreted in the context of previous research from the fields of attention, music cognition, motor control and rhythm processing, and invite an integrated perspective on how the brain coordinates its activities in time. This integrated approach has the potential to provide a more comprehensive understanding of disorders such as ADHD and Parkinson’s disease, in which symptomologies span both cognitive and motor deficits, and paves the way for the development of better-targeted treatments to harness the transformative powers of music and rhythm.