Attentional and affective responses to complex musical rhythms

I investigated how two types of rhythmic complexity, syncopation and tempo fluctuation, affect the neural and behavioral responses of listeners. The aim of Experiment 1 was to explore the role of attention in pulse and meter perception using complex rhythms. A selective attention paradigm was used in which participants attended either to a complex auditory rhythm or a visually presented list of words. Performance on a reproduction task was used to gauge whether participants were attending to the appropriate stimulus. Selective attention to rhythms led to increased BOLD (Blood Oxygen Level-Dependent) responses in basal ganglia, and basal ganglia activity was observed only after the rhythms had cycled enough times for a stable pulse percept to develop. These observations show that attention is needed to recruit motor activations associated with the perception of pulse in complex rhythms. Moreover, attention to the auditory stimulus enhanced activity in an attentional sensory network including primary auditory, insula, anterior cingulate, and prefrontal cortex, and suppressed activity in sensory areas associated with attending to the visual stimulus. In Experiment 2, the effect of tempo fluctuation in expressive music on emotional responding in musically experienced and inexperienced listeners was investigated. Participants listened to a skilled music performance, including natural fluctuations in timing and sound intensity that musicians use to evoke emotional responses, and a mechanical performance of the same piece, that served as a control. Participants reported emotional responses on a 2-dimensional rating scale (arousal and valence), before and after fMRI scanning. During fMRI scanning, participants listened without reporting emotional responses. Tempo fluctuations predicted emotional arousal ratings for all listeners. Expressive performance was associated with BOLD increases in limbic areas for all listeners and in limbic and reward related areas for those with musical experience. Activity in the dorsal anterior cingulate, which may reflect temporal expectancy, was also dependent on the musical experience of the listener. Changes in tempo correlated with activity in a mirror neuron network in all listeners, and mirror neuron activity was associated with emotional arousal in experienced listeners. These results suggest that emotional responding to music occurs through an empathic motor resonance.