Master of Science
Grahn, Jessica A.
Humans have an intrinsic tendency to move to music. However, our understanding of the neural mechanisms underlying the music-movement connection remains limited, and most studies have used correlational methods. Here, we used transcranial direct current stimulation (tDCS) to causally investigate the role of four motor brain regions involved in movement timing and beat perception: the supplementary motor area (SMA), left and right premotor cortices (PMC), and cerebellum. Subjects were randomly assigned to a brain region to be stimulated and received anodal, cathodal, or sham stimulation on three different days while they reproduced rhythmic sequences. The sequences had either a strong beat percept, weak beat percept, or no beat percept. We predicted that SMA stimulation would affect reproduction of strong beat rhythms, whereas PMC and cerebellar stimulation would affect reproduction of weak or non-beat rhythms. No difference in reproduction accuracy was found based on brain region or type of stimulation.
Summary for Lay Audience
Humans have an intrinsic tendency to move to music, perhaps because motor brain areas respond to beat perception. However, our understanding of the neural mechanisms underlying the music-movement connection remains limited, and most studies have used correlational methods, such as fMRI, and other neuroimages methods. Here, we investigated the role of four motor brain regions involved in the timing of movement and beat perception: the supplementary motor area (SMA), the left and right premotor cortex (PMC), and the right cerebellum, using transcranial direct current stimulation (tDCS). TDCS is a causal method that modulates brain responses in two opposite directions: anodal stimulation increases cortical excitability, and cathodal stimulation inhibits cortical excitability. Subjects were randomly assigned to receive stimulation in one of the four brain regions. They participated in three sessions separated from two to seven days, receiving anodal, cathodal, or sham stimulation in each session while they reproduced different types of rhythmic sequences. In some sequences, a beat was easily perceived; in others, the beat was unclear or absent. As the SMA plays a primary role in beat perception, while the premotor cortex and cerebellum appear to have a general role in timing, we predicted that the SMA stimulation would affect reproduction of rhythms with a beat, whereas premotor and cerebellar stimulation would affect reproduction of sequences with no beat. As expected, regardless of the brain region, improved reproduction was observed according to whether the rhythm had a beat or not, but no difference was found based on the stimulation received. Thus, we found no evidence that modulating brain excitability alters the accuracy of rhythm reproduction. We discuss the implications of these results and the future perspectives for this research.
Emerick, Marina, "The Effects Of Transcranial Direct Current Stimulation On Beat Perception And Motor Performance" (2022). Electronic Thesis and Dissertation Repository. 8797.
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