Despite the amazing level of shared neural machinery between humans and nonhuman primates, only humans appear to spontaneously ‘feel the beat’ in rhythm. Moving to the beat has played a significant role in human culture for millennia, but the mechanism underlying beat perception is still a mystery. Existing models of time perception cannot account for many features of beat perception, and behavioral 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 respond to rhythm, and certain motor areas respond specifically during beat perception, even when no movement is made. My research will continue to investigate the beat-based system with three inter-related streams that aim to: i) understand the neural mechanisms of rhythm and beat perception, ii) compare brain responses across species, assessing whether beat perception is truly unique to humans, iii) exploit beat-based mechanisms for gait interventions in movement disorders.
The first stream will examine what roles are played by the 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 beat-based timing. To investigate this, I will apply noninvasive brain stimulation to transiently disrupt functioning in individual motor areas, measuring how each supports timing and beat perception.
Most non-human primates can time the short intervals that make up rhythms, but appear insensitive to the beat. Beat perception may be unique to humans, or primates may perceive the beat, but have not been tested with paradigms that can demonstrate beat sensitivity. Therefore, I will compare brain responses in humans and other primates to beat-based sequences and nonbeat-based sequences, using non-invasive 7 Tesla MRI. If the brains of other primates distinguish beat and nonbeat sequences, this challenges the currently held view that beat perception is uniquely human.
In humans, beat perception not only activates motor areas, but enhances communication between auditory and motor areas in the brain, providing a pathway by which sound can influence movement. My third research stream will exploit this connection, characterizing how selected rhythmic and musical characteristics alter walking, enabling us to select optimal music features for gait interventions for patients with movement disorders, such as Parkinson’s disease. I will also characterize the neural pathways that enable different features of music and rhythm features to improve movement at an individual level. Currently, patients’ responses to musical gait interventions vary widely. My goal is to assess and account for these individual differences and thus tailor musical interventions to individual patients.
Understanding the neurobiological foundations of beat perception and rhythm will shape future theories about our fundamental timing capacities and their underlying mechanisms. Determining whether some capacities, such as beat-based timing, are uniquely human will be crucial to creating accurate models of timing and temporal perception. These models will have widespread applicability, as temporal perception underlies our capacity to integrate information from different senses, coordinate movement, and perceive relationships in the world.