Grant: Discovery Grants Program - Individual

Summary: Moving to a steady musical beat is one of myriad human behaviours that rely on regularity (e.g., walking, talking, turn-taking), but the mechanisms underlying beat sensitivity are still unclear. Beat perception occurs spontaneously when we listen to rhythmic sequences of time intervals, and more readily for auditory than visual sequences. Existing non-beat-based (or interval-based) models of time perception, based largely on animal data, cannot account for many features of beat perception, and behavioral evidence indicates that humans may have a unique beat-based timing system. The long-term goal of my research is to determine the behavioural and neural mechanisms of beat-based timing, and how this system relates to the more-studied non-beat-based system. That goal is supported by the current proposal's three short-term objectives: i) develop novel behavioural paradigms to test how beat-based and non-beat-based timing relate using tightly controlled auditory and visual stimuli, ii) establish the neural mechanisms of beat-based and non-beat-based timing across explicit and implicit timing tasks using advanced multivariate neuroimaging techniques, and iii) conduct novel cross-species comparisons of neural responses to beat-based and non-beat-based stimuli to examine whether beat perception is unique to humans among primates. In Project 1, my trainees and I will develop and validate a new paradigm to assess whether single-interval timing, non-beat-based sequence timing, and beat-based sequence timing are a stages of a single hierarchically organized timing process, with each stage dependent on the previous, or if beat-based timing operates independently of other timing systems, perhaps in a modality-specific way. In Project 2, we will use recently-developed multivariate analyses of neuroimaging data to examine whether the basal ganglia and cerebellum are the `core' computational hubs that underpin beat-based and non-beat-based timing systems, and resolve conflicting observations about whether these systems operate for both explicit and implicit timing. Finally, Project 3 uses ultrahigh-field 9.4Tesla MRI to compare neural responses to beat-based and non-beat-based sequences in humans and marmosets. Understanding the mechanisms of beat-based timing are crucial to creating accurate behavioural, neural, and computational models of timing behaviour, which has implications beyond music. Timing is crucial for speech, motor control, and anticipation of relevant environmental events. Clinically, a steady beat has been used to mitigate disorders of gait in Parkinson's, Huntington's, and stroke, but neither the underlying mechanisms nor how to optimize the effects across different neurological disorders is understood. In addition, beat perception deficits relate to dyslexia and stuttering. Understanding the neural mechanisms that mediate this relationship could lead to effective interventions that selectively target the beat-based system.