Rats synchronize predictively to metronomes

Abstract

Humans easily and naturally synchronize their motor activity to music, a behavior unparalleled by other species. As a consequence of the mystery surrounding its evolutionary and biological origins, there is rapidly growing interest in exploring the capacity of nonhuman species to synchronize motor activity with auditory rhythms. The hallmark observation in human studies is that synchronization is predictive. Given the highly variable behaviors observed in other animals, it is particularly difficult to distinguish a predictive synchronization behavior from one that perhaps resembles it, but relies on simpler strategies. Here, we introduce a novel modeling approach that quantitatively compares candidate strategies for explaining observed behaviors. Eight rats synchronized to metronomes across a range of tempi (0.5-2 Hz), and immediate water reward was delivered whenever they initiated a lick burst within a short time window around beats. We observed a roughly constant baseline lick probability throughout, with a [~]30% modulation of the lick rate around beats. We fitted to the results six candidate models, ranging from an insensitive model assuming that rats lick at random, to predictive models where rats suppress licking between beats for a tempo-dependent duration of time. The predictive model consistently outperformed other models, including a reactive model, demonstrating that rats synchronize predictively to auditory metronomes.