Moving with precision to a musical beat is considered a skill uniquely human. However, new research now shows that mice have this ability as well. The optimal rhythm for nodding depends on the time constant in the brain (the speed at which our brain can respond to something), which is the same for all species. This means that the ability of our auditory and motor systems to communicate and move to music may be more widespread across species than previously thought. This new discovery not only offers deeper insight into the animal spirit, but also into the origins of our own music and dance.
Can you move to the beat or do you have two left feet? Apparently, how we can time our movement to music is somewhat dependent on our innate genetic ability, and this skill was once thought to be a uniquely human trait. Although animals also respond to auditory noise, or may make rhythmic sounds, or are trained to respond to music, this is not the same as the complex neural and motor processes that work together to allow us to naturally recognize rhythm of a song, responding to it or even predicting it. This is called beat synchronicity.
It’s only relatively recently that research studies (and home videos) have shown that some animals seem to share our desire to move into the groove. A new paper from a team at the University of Tokyo provides proof that mice are one of them. “The rats show innate synchronization – that is, without any prior training or exposure to music – the synchronization of beats that is most noticeable between 120 and 140 bpm (beats per minute ), where humans also show the clearest beat synchronization,” explains Associate Professor Hirokazu Takahashi. from the Graduate School of Information Science and Technology. “The auditory cortex, the region of our brain that processes sound, is also tuned to 120-140 bpm, which we were able to explain using our mathematical model of brain adaptation. »
But why play music to mice in the first place? “Music has a strong pull on the brain and has a profound effect on emotion and cognition. To effectively use music, we need to reveal the neural mechanism underlying this empirical fact,” said Takahashi. “I am also a specialist in electrophysiology, which looks at electrical activity in the brain, and I have studied the auditory cortex of rats for many years. »
The team has two alternative hypotheses: the first is that the optimal music tempo for beat synchronicity is determined by the body’s time constant. It differs between species and is faster for small animals than for humans (think how fast a rat can scuttle itself). The second is that the optimal tempo is instead determined by the brain’s time constant, which is surprisingly similar across species. “After conducting our research on 20 human participants and 10 mice, our results suggest that the optimal tempo for beat synchronization depends on the time constant in the brain,” Takahashi said. “This shows that the animal brain can be useful in elucidating the perceptual mechanism of music. »
The mice were equipped with miniature wireless accelerometers capable of measuring the smallest head movements. Human participants also wore accelerometers in headphones. They were then played a one-minute excerpt from Mozart’s Sonata for Two Pianos in D Major, K. 448, at four different tempos: seventy-five percent, 100 percent, 200 percent, and 400 percent of the speed. ‘source. The original tempo was 132 bpm and the results showed that the beat synchronicity of the rats was most pronounced in the range of 120-140 bpm. The team also found that mice and humans shook their heads in time to the beat at similar rates, and that the level of head shaking decreased as the music sped up.
“To the best of our knowledge, this is the first report of innate beat synchronization in animals that has not been achieved through training or exposure to music,” Takahashi said. “We also hypothesized that short-term adaptation in the brain is involved in beat tuning in the auditory cortex. We were able to explain this by fitting our neural activity data to a mathematical model of adaptation. Moreover , our adaptation model showed that in response to random click sequences, peak beat prediction performance occurred when the mean interval between stimuli (the time between the end of one stimulus and the onset of another) is about 200 milliseconds (one-thousandth of a second). internote interval in classical music, suggesting that this property of adaptation in the brain underlies the perception and creation of music . »
As well as being a fascinating insight into the animal spirit and the construction of our own rhythmic synchronicity, researchers also see it as insight into the creation of music itself. “Next, I want to reveal how other musical properties such as melody and harmony are related to brain dynamics. I am also interested in how, why and what brain mechanisms create human cultural fields such as art, music, science, technology and religion,” Takahashi said. “I believe this question is the key to understanding how the brain works and building the next generation AI (artificial intelligence). Also, as an engineer, I am interested in using music for a happy life. »
Materials provided by University of Tokyo. Note: Content may be edited for style and length.