Auditory rhythm complexity affects cardiac dynamics during perception and production

Perception and production of auditory rhythms are key capacities for human behaviors such as speech and music. Auditory rhythms in music range in the complexity of successive tone durations; complex rhythms (based on non-integer duration ratios) are more difficult to perceive and produce than simple rhythms (based on integer ratios). The physiological activity supporting this behavioral difference is not well understood. In a within-subjects design, we addressed how rhythm complexity affects cardiac dynamics during auditory perception and production. Musically trained adults listened to and synchronized with simple and complex auditory rhythms while their cardiac activity was recorded. Participants identified missing tones in the rhythms during the Perception condition and produced finger taps to synchronize with the rhythms in the Synchronization condition. Participants were equally accurate at identifying missing tones in both rhythms during the Perception condition. Tapping synchronization was less accurate and less precise with complex rhythms than with simple rhythms. Linear cardiac analyses showed a slower mean heart rate and greater heart rate variability during perception than production, for both simple and complex rhythms. Individual differences showed that greater heart rate variability was correlated with poorer synchronization. Linear and nonlinear cardiac analyses identified perception / synchronization differences; only nonlinear recurrence quantification analyses captured cardiac differences between simple and complex auditory rhythms. Cardiac dynamics were also more deterministic (predictable) during rhythm perception than synchronization. Overall, these findings suggest that cardiac activity is modulated by both task (auditory perception, production) and by rhythm complexity.