Mechanisms of rhythm perception

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Moving to a musical beat is one of myriad human behaviours that rely on regularity (e.g., walking, talking, turn-taking), but the mechanisms underlying our sensitivity to a regular beat are still a mystery. Beat perception occurs spontaneously, without effort, when we listen to rhythmic sequences of time intervals. Existing models of time perception cannot account for many features of beat perception, and behavioural evidence suggests that humans may have a unique beat-based timing system. My research seeks to characterize this system. Thus far, my research indicates a link between beat perception and movement: brain areas that control movement are activated when we hear rhythm, and certain motor areas respond specifically during beat perception, even when no movement is made. I aim to: i) develop tools to assess beat perception independently from beat production, ii) characterize the timecourse of the motor system's role in beat perception, and iii) combine brain stimulation and imaging methods to understand the causal roles of specific motor areas in rhythm and beat perception.***In the first research project, my trainees and I will validate a novel paradigm to assess beat perception. The paradigm enables us to determine the timecourse of beat induction' (finding the regular beat in a rhythmic sequence), and to examine how and why this timecourse varies across individuals. In the second project, we will use transcranial magnetic stimulation (TMS) to measure motor system excitability during beat perception. The timecourse of motor excitability (e.g., does it fluctuate in anticipation of each upcoming beat, or in reaction to the beat) will inform us about the role of the motor system during beat induction and beat perception. Further, we will examine whether musical experience and individual differences in rhythmic ability are reflected in the degree or latency of motor excitability changes. The third project will examine the causal roles played by individual motor areas that respond during rhythm and beat perception. Some roles may be general to all types of timing, whereas others may be specific to timing based on the beat. To investigate this, we will apply noninvasive brain stimulation to transiently disrupt, as well as enhance, functioning in individual motor areas, measuring how each supports timing and beat perception. ***Understanding the mechanisms of beat and rhythm perception will be crucial to creating accurate models of humans' complex timing behaviour, but also has implications for many domains beyond music. Temporal perception underlies our capacity to integrate information from different senses, coordinate movement, and perceive relationships in the world. Clinically, beat perception predicts language and hearing skills, and forms the basis of music-based gait interventions.