Undergraduate Honors Theses

Date of Award

Spring 4-7-2017




Jessica Grahn, Ph.D.


The ability to anticipate complex sounds, like words in speech or the beat in music, is an important aspect of human perception. However, the changes of excitability in the motor system during auditory anticipation have not been characterized. Here, we applied single-pulse Transcranial Magnetic Stimulation (TMS) to the primary motor cortex to elicit motor evoked potentials (MEPs) from the first dorsal interosseous muscle, the amplitude of which indexes motor system excitability. Healthy right-handed participants (N = 20) underwent TMS stimulation during listening to regular (periodic) tone sequences at three rates (200ms, 550ms, and 900ms) and irregular tone sequences. We assessed MEP amplitudes over time, to test fluctuations in excitability during auditory anticipation (listening to regular sequences), and in the absence of auditory anticipation (listening to irregular sequences). We hypothesize that motor system excitability fluctuates at the rate of auditory stimulation, and peaks in anticipation of regular sounds. Results do not show evidence that motor system excitability fluctuates at the rate of regular or irregular auditory tones. Also, the results do not show evidence of an increase in excitability in anticipation of regular or irregular sounds. These results do not suggest synchronization of motor system excitability to regular sounds, informing our understanding of auditory-motor integration.