Summary: New findings reveal that rats can move their heads to the beat of music, showing that animals have an innate ability to synchronize rhythms.
Source: University of Tokyo
It was believed that the precise transition to the rhythm of music is a skill inherent in humans. However, new research now shows that rats also have this ability.
The optimal rate of nodding was found to depend on a time constant in the brain (the speed at which our brain can respond to something) that is similar across species. This means that the ability of our auditory and motor systems to interact and move to music may be more common across species than previously thought.
This new discovery offers not only greater insight into the animal mind, 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 well we are able to match our movement to music depends to some extent on our innate genetic ability, a skill previously thought to be a uniquely human trait.
Although animals also respond to auditory noise, or can produce 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 the rhythm of a song. react to it or even anticipate it. This is called beat synchrony.
Only relatively recently have studies (and home videos) shown that some animals seem to agree with our desire to get into the groove. New work from a team at the University of Tokyo provides evidence that rats are one of them.
“Rats show innate, that is, without any training or prior exposure to music, beat synchronization most clearly at 120-140 beats per minute (beats per minute), so humans also have the clearest beat synchronization,” explained Associate Professor Hirokazu Takahashi of Information Science and university of technology.
“The auditory cortex, the region of our brain that processes sound, was also tuned to 120-140 beats per minute, which we were able to explain using our mathematical model of brain adaptation.”
But why play music for rats at all?
“Music strongly affects the brain and has a profound effect on emotion and cognition. To use music effectively, we need to discover the neural mechanism underlying this empirical fact,” said Takahashi.
“I’m also a specialist in electrophysiology, which deals with electrical activity in the brain, and I’ve studied the auditory cortex of rats for many years.”
The team had two alternative hypotheses: the first was that the optimal music tempo for beat synchrony would be determined by the body’s time constant. This varies between species and is much faster in small animals compared to humans (think about how fast a rat can slide).
The second was that the optimal pace would instead be determined by the brain’s time constant, which is strikingly similar across species.
“After conducting our study with 20 humans and 10 rats, our results show that the optimal rate of beat synchronization depends on the time constant in the brain,” Takahashi said.
“This shows that animal brains can be useful for elucidating the mechanisms of music perception.”
The rats were fitted with wireless, miniature accelerometers that could measure the smallest head movements.
Human participants also wore accelerometers in headphones. They were then played one-minute excerpts from Mozart’s Sonata for Two Pianos in D Major, K. 448, at four different tempos: seventy-five percent, 100%, 200%, and 400% of the original speed.
The initial pace is 132 beats per minute, and the results showed that the synchrony of the rats’ beats was most clear in the range of 120 to 140 beats per minute.
The team also found that both rats and humans jerked their heads in a similar rhythm, and that the rate of head jerking decreased as the music was sped up.
“To our knowledge, this is the first report of innate beat synchronization in animals that was not achieved through training or musical exposure,” Takahashi said.
“We also hypothesized that short-term adaptation in the brain was related to beat regulation in the auditory cortex. We were able to explain this by fitting our neural activity data to a mathematical model of adaptation.
“Furthermore, our adaptation model showed that in response to random click sequences, the greatest hit prediction performance occurred when the average interstimulus interval (the time between the end of one stimulus and the beginning of another stimulus) was about 200 milliseconds (one thousandth of a second).
“This was consistent with the statistics of internote intervals in classical music, suggesting that an adaptive property in the brain underlies the perception and creation of music.”
The researchers see this not only as a fascinating insight into the animal mind and the evolution of our own rhythmic synchronicity, but also as an insight into the creation of music itself.
“Next, I would like to discover how other properties of music, such as melody and harmony, are related to brain dynamics. I am also interested in how, why, and what brain mechanisms produce fields of human culture, such as fine arts, music, science, technology and religion,” Takahashi said.
“I believe this question is central to understanding how the brain works and developing the next generation of AI (artificial intelligence). As an engineer, I am interested in using music for a happy life.
Funding: This work was supported in part by JSPS KAKENHI (20H04252, 21H05807) and JST Moonshot R&D Program (JPMJMS2296).
About this music and neuroscience research news
Author: Joseph Krisher
Source: University of Tokyo
Contact person: Joseph Krischer – University of Tokyo
Image: The image is in the public domain
Preliminary study: Open access.
Hirokazu Takahashi et al. “Spontaneous beat synchronization in rats: neural dynamics and motor involvement”. Science Translational Medicine
Spontaneous beat synchronization in rats: neural dynamics and motor involvement
Beat perception and synchronization of 120 to 140 beats per minute (BPM) is common in humans and often used in musical composition. Why beat synchronization is not common in some species, and the mechanism that determines the optimal tempo, is unclear.
Here, we examined physical movements and neural activity in rats to determine their shock sensitivity.
Careful examination of head movements and neural recordings revealed that the rats exhibited marked beat synchronization and activity in the auditory cortex between 120 and 140 beats per minute. Mathematical modeling suggests that this rhythm regulation is based on short-term adaptation.
Our results support the hypothesis that the optimal rate of beat synchronization is determined by the time constant of neural dynamics conserved across species, rather than by the species-specific time constant of physical movements. Thus, the latent neural propensity for auditory motor recruitment may provide a basis for human involvement that is much more widespread than currently believed.
Future studies comparing humans and animals will provide insight into the origins of music and dance.