Rats can spontaneously discriminate different rhythms: An investigation using an automated habituation-dishabituation paradigm

Vocal production learning has been thought to be necessary for rhythmic cognition. However, recent studies have shown that rats, a non-vocal production learning species, are capable of discriminating rhythms and synchronizing to rhythm. Here, we investigated whether rats can spontaneously discriminate between different rhythms by using three types of rhythmic sound stimuli that differ only in the ratio of time intervals. In the experiment, we tested 30 rats by using a newly developed automated habituation-dishabituation paradigm implemented with the recent cutting-edge real-time animal tracking technology. The sound stimulus was automatically switched to a different type of rhythmic time interval ratio depending on the tracked animal's movement activity. For all rhythm orders, sound type switching increased the distance travelled by the rats, suggesting that rats can discriminate between rhythms that differ only in the ratio of time intervals. These results indicate that non-vocal production learning species may also be able to recognize the periodic temporal structure of rhythms.