The effect of rhythmic and harmonic complexity on motor and reward networks.
Tomas Matthews, Concordia University, Montreal, Canada
Virginia Penhune, Concordia University, Montreal, Canada
Peter Vuust, Aarhus University and Royal Academy of Music, Denmark
Torben Lund, Center of Functionally Integrative Neuroscience, Aarhus, Denmark
When the music of Sister Sledge, Stevie Wonder or Missy Elliott comes on the radio, many of us find it hard to sit still, and may start tapping our feet, bobbing our heads or maybe even get up and dance. What is it about certain music that makes us want to move? And why does moving to the music feel so good?
Few musical contexts make the pleasurable effect of music more apparent than the dance club. Yet we still know little about the cognitive and neural mechanisms underlying the pleasurable desire to move to music, a sensation that is known as groove.
A prominent structural feature of groove-directed music (e.g. funk, soul, hip-hop, electronic dance music, disco, afrobeat, reggae, dancehall and jazz) is repeated syncopation. Syncopation is a form of rhythmic complexity where the notes fall off instead of on the beat, which is otherwise regular. Previous research has shown that intermediate levels of syncopation are the most effective in eliciting the sensation of groove – that is, we prefer rhythms that are neither too complex nor too simple, but instead have a perfect balance of on-beat and off-beat rhythmic phrasing. But it is not just the complexity of the rhythm that is important. For example, the complexity of the harmony can also affect the sensation of groove.
In this study, we were interested in understanding how rhythmic syncopation and harmonic complexity interact in the sensation of groove, and how this interaction is reflected in the neural activity of the brain. In particular, we wanted to see how motor and reward networks in the brain were affected by groove. The motor network is responsible for planning, imagining and executing movements, while the reward network is crucial for experiencing pleasure and emotion. We focused specifically on a collection of regions called the Basal Ganglia, since these are known to be important for both movement and pleasure.
To test the effects of groove on the brain, we used brain imaging techniques (fMRI) to measure participants brain activity while they listened to rhythmic patterns varying in rhythmic syncopation and harmonic complexity. While in the scanner, listeners also rated their experience of wanting to move and pleasure in response to the patterns.
We found that both motor and reward areas networks were activated during medium levels of rhythmic and harmonic complexity, which were also rated as eliciting the most wanting to move and the most pleasure. Furthermore, there was an interaction between rhythmic syncopation and harmonic complexity in parts of the Basal Ganglia, suggesting that this region may be an important area where body-movement and pleasure is integrated during the sensation of groove. Specifically, activity in the region increased when medium rhythmic syncopation was combined with medium harmonic complexity. This interaction was especially prominent for the musicians taking part in the study, indicating that listeners’ previous experience with music affects their neural responses
The study provides new evidence for how motor and reward processes intersect during musical experiences, and contributes to our understanding of how and why certain music makes people want to move. The work could also have therapeutic applications, especially for therapies treating motor dysfunctions, such as Parkinson’s Disease. If groove integrates motor and reward processing, then perhaps groove can provide a more motivating and rewarding context for treating motor symptoms than traditional music therapies.