Undergraduate Honors Theses

Date of Award

Spring 4-5-2017




Jessica Grahn

Second Advisor

Daniel Cameron


Humans tend to spontaneously move to the regular beat of musical rhythm. Beat perception is the tendency to sense and anticipate the regular time positions (beats) that movements synchronize with. The neural motor system plays an important role in beat perception, but the dynamics of excitability in the motor system associated with beat perception have not been characterized. This project investigated motor system excitability fluctuations using transcranial magnetic stimulation and electromyography during perception of beat-based and non-beat-based rhythms. We applied single-pulse TMS over the left primary motor cortex of healthy participants as they listened to three types of rhythms that varied in the degree to which they induced beat perception. TMS elicited motor evoked potentials (MEPs) from the first dorsal interosseous muscle. MEP amplitude serves as a proxy for real-time motor system excitability. We hypothesized that during beat perception, motor system excitability may fluctuate at the rate of the perceived beat. We found that beat perception was not associated with anticipatory increases in motor system excitability, or with ongoing fluctuations in excitability at multiple rates associated with the beat. These results inform our understanding of the neural mechanisms of beat perception, as well as potential therapeutic uses of music, for example in Parkinson’s disease.