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Abstract:
Auditory tasks such as understanding speech and listening to music rely on the ability to track sound sequences and adjust attention based on the temporal cues they contain. An entrainment approach proposes that internal oscillatory mechanisms underlie the ability to synchronize with rhythms in the external world. Here, we aimed to understand the factors that facilitate and impede rhythm processing by investigating the interplay between the properties of external and internal rhythms. We focused on two key properties of an oscillator: its preferred rate, the default rate at which it oscillates in the absence of input, and flexibility, its ability to adapt to changes in rhythmic context. We hypothesized that flexibility would be diminished with advancing age. Experiment 1 was a two-session duration discrimination paradigm where we developed methods to estimate preferred rate and flexibility and assessed their reliability. Experiment 2 involved a shorter version of this paradigm and a paced tapping task with matched stimulus conditions, in addition to a spontaneous motor tempo (SMT) and two preferred perceptual tempo (PPT) tasks that measured motor and perceptual rate preferences, respectively. Preferred rates, estimated as the stimulus rates with the best performance, showed a harmonic relationship across sessions (Experiment 1) and were correlated with SMT (Experiment 2). Interestingly, estimates from motor tasks were slower than those from the perceptual task, and the degree of slowing was consistent for each individual. To challenge an individual’s oscillator flexibility, we maximized the differences in stimulus rates between consecutive trials in the duration discrimination and paced tapping tasks. As a result, performance in both tasks decreased, and performance on individual trials indicated a gravitation toward the stimulus rate presented in the preceding trial. Critically, flexibility, quantified as an individual’s ability to adapt to faster-than-previous rates, decreased with age. Overall, these findings show domain-specific rate preferences for the assumed oscillatory system underlying rhythm perception and production, and that this system loses its ability to flexibly adapt to changes in the external rhythmic context during ageing.
