The Influence of Familiarity on Neural Correlates of Rhythm and Beat Perception
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.