Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Neuroscience
Supervisor
Grahn, Jessica A.
Abstract
Music evokes the sensation of a steady pulse, or ‘beat’. The beat arises from the regular rhythm in music, and is associated with neural motor region activation and synchronized electrical activity. This thesis investigates how activity in motor regions may encode stimulus features of rhythm, including beat strength, and tests whether neural correlates of beat perception are influenced by rhythm familiarity, regardless the beat.
Chapter 1 describes past literature on rhythm and beat perception, including neural correlates detected via functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), and how differences in beat strength affect behaviour.
Chapter 2 reports research on the encoding of rhythm across the brain. Fine-grained multi-voxel activity patterns were measured using fMRI during rhythm listening. We show that the supplementary motor area (SMA) and putamen reliably encode beat strength in their activity patterns. Activity patterns did not only reflect our 3 beat strength conditions, but were sensitive even to small differences in beat strength between individual rhythms, suggesting that the SMA and putamen do not simply activate or deactivate in the presence and absence of beat, but encode the strength of the beat for each rhythm.
Chapter 3 reports research testing the influence of familiarity on beat-sensitive regions identified in Chapter 2. Participants were scanned twice – before and after learning rhythms via a training paradigm. In both pre- and post-training, the SMA and putamen activated in highly dissimilar patterns for rhythms of different beat strengths, suggesting the regions are indeed encoding beat strength and are not influenced by familiarity.
Chapter 4 reports research testing the influence of familiarity on oscillatory entrainment to rhythm. Here, the same training paradigm was used as in Chapter 3, except that EEG recording replaced the pre- and post-training fMRI sessions. Like Chapter 3, no influence of familiarity on neural entrainment to beat and rhythm was found – strong-beat rhythms elicited the greatest neural entrainment to the beat in both pre- and post-training sessions.
Chapter 5 provides a general discussion of the findings in Chapters 2-4 and relates the implications of the current work to previous literature in the field of rhythm and beat perception, and more broadly for mechanisms of timing. Limitations and future directions are also discussed.
Summary for Lay Audience
When listening to music, humans ubiquitously feel and spontaneously synchronize movements in time with an underlying pulse, or ‘beat’. Only well-trained animals appear to synchronize with the beat, suggesting that the human nervous system is specially equipped for spontaneous beat perception. Though neural activity associated with perceiving the beat has been well studied, no studies have disentangled beat perception from our general familiarity with musical rhythm – because we listen to music in our daily lives, we are much more familiar with rhythms that have a beat, and unfamiliar with rhythms that are irregular and have no beat at all. Thus, comparing brain responses for beat and no beat rhythms may be confounded by differences in familiarity, not just differences in beat. Here we conducted 3 experiments to better characterize the neural activity associated with rhythm and beat perception by using novel analysis techniques, and by training individuals to be highly familiar with rhythms that have a beat and rhythms with no beat. This enabled us to determine what brain responses were associated with beat perception while controlling for familiarity. In general, the results show that even well-learned rhythms that have no beat do not elicit the same neural activity as rhythms with a strong beat. This suggests that beat-related neural correlates are indeed involved in extracting or generating the beat during music listening, and not just predicting familiar sounds.
Recommended Citation
Hoddinott, Joshua, "The Influence of Familiarity on Neural Correlates of Rhythm and Beat Perception" (2024). Electronic Thesis and Dissertation Repository. 10401.
https://ir.lib.uwo.ca/etd/10401
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.