Production of regular rhythm induced by external stimuli in rats.

Rhythmic ability is important for locomotion, communication, and coordination between group members during the daily life of animals. We aimed to examine the rhythm perception and production abilities in rats within the range of a subsecond to a few seconds. We trained rats to respond to audio-visual stimuli presented in regular, isochronous rhythms at six time-intervals (0.5-2 s). Five out of six rats successfully learned to respond to the sequential stimuli. All subjects showed periodic actions. The actions to regular stimuli were faster than randomly presented stimuli in the medium-tempo conditions. In slower and faster tempo conditions, the actions of some subjects were not periodic or phase-matched to the stimuli. The asynchrony regarding the stimulus onset became larger or smaller when the last stimulus of the sequence was presented at deviated timings. Thus, the actions of the rats were tempo matched to the regular rhythm, but not completely anticipative. We also compared the extent of phase-matching and variability of rhythm production among the interval conditions. In interval conditions longer than 1.5 s, variability tended to be larger. In conclusion, rats showed a tempo matching ability to regular rhythms to a certain degree, but maintenance of a constant tempo to slower rhythm conditions was difficult. Our findings suggest that non-vocal learning mammals have the potential to produce flexible rhythms in subsecond timing.