Summary: New findings show that rats can move their heads in time to music, showing animals have innate clock synchronization.
Source: University of Tokyo
It was believed to be an ability to move precisely to a musical beat, an ability inherently unique to humans. However, new research now shows that rats also have this ability.
It has been found that the optimal pace for nodding along depends on the brain time constant (the speed at which our brain can react to something), which is similar across species. This means that the ability of our auditory and motor systems to interact and move with music may be more widespread among species than previously thought.
This new discovery not only offers further insight into animal minds, but also into the origins of our own music and dance.
Can you move to the beat or do you have two left feet? How well we can match our movement to music appears to depend somewhat on our innate genetic ability, and this ability was once thought to be a uniquely human trait.
While animals also respond to auditory sounds, or make rhythmic noises, 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 beat in a song. react to it or even predict it. This is called isochronous mode.
Only relatively recently have research studies (and home movies) shown that some animals seem to share our urge to move to the groove. A new paper from a team at the University of Tokyo provides evidence that rats are one of them.
“Rats showed innate – that is, without training or prior exposure to music – beat synchronization most clearly within 120-140 bpm (beats per minute), to which humans also show the clearest beat synchronization,” explained Associate Professor Hirokazu Takahashi of the Graduate School of Information Science and technology.
“The auditory cortex, the region of our brain that processes sound, was also locked at 120-140 BPM, which we were able to explain using our mathematical model of brain adaptation.”
But why play music for rats at all?
“Music exerts a powerful attraction on the brain and has profound effects on emotions and cognition. To use music effectively, we need to uncover the neural mechanism underlying this empirical fact,” Takahashi said.
“I’m also a specialist in electrophysiology, which studies electrical activity in the brain, and have been studying the auditory cortex of rats for many years.”
The team had two alternative hypotheses: the first was that the optimal music tempo for clock synchrony would be determined by the body’s time constant. This varies between species and is much faster in small animals than in humans (remember how fast a rat can scurry).
The second was that the optimal pace would instead be determined by the brain’s time constant, which is surprisingly similar across species.
“After conducting our research with 20 human participants and 10 rats, 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 mechanisms of music.”
The rats were equipped with miniature wireless accelerometers that could measure the slightest head movements.
Human participants also wore accelerometers on headphones. They were then played one-minute excerpts from Mozart’s Sonata for Two Pianos in D major K. 448 at four different tempos: 75%, 100%, 200% and 400% of the original speed.
The original tempo is 132 bpm and the results showed that the clock synchronicity of the rats was most evident in the range of 120 to 140 bpm.
The team also found that both rats and humans moved their heads in a similar rhythm to the beat, and that the intensity of the head jerk decreased as the music was sped up.
“To the best of our knowledge, this is the first report of innate clock synchronization in animals that has not been achieved through training or musical exposure,” 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 fitting.
“Furthermore, our fitting model showed that in response to random click sequences, the highest beat prediction performance occurred when the mean interstimulus interval (the time between the end of one stimulus and the start of another) was around 200 milliseconds (one-thousandths of a second).
In addition to a fascinating insight into the animal mind and the development of our own clock synchronicity, the researchers also see it as a glimpse into the creation of music itself. The image is in the public domain
“This was consistent with statistics of internote intervals in classical music, suggesting that the adaptive property in the brain underlies the perception and creation of music.”
In addition to a fascinating insight into the animal mind and the development of our own clock synchronicity, the researchers also see it as a glimpse into the creation of music itself.
See also
“Next, I would like to show how other musical properties, such as melody and harmony, are related to the dynamics of the brain. I am also interested in how, why and which brain mechanisms create human cultural fields such as fine arts, music, science, technology and religion,” said Takahashi.
“I believe this question is key to understanding how the brain works and developing next-generation AI (artificial intelligence). Also, as an engineer, I am interested in using music for a happy life.”
Financing: This work was supported in part by JSPS KAKENHI (20H04252, 21H05807) and the JST Moonshot R&D program (JPMJMS2296).
About this news from music and neuroscience research
Author: Joseph Krisher
Source: University of Tokyo
Contact: Joseph Krisher – University of Tokyo
Picture: The image is in the public domain
Original research: Open access.
“Spontaneous beat synchronization in rats: neural dynamics and motor entrainment” by Hirokazu Takahashi et al. Science Translational Medicine
abstract
Spontaneous beat synchronization in rats: neural dynamics and motor entrainment
Beat perception and synchronization within 120 to 140 beats per minute (BPM) is common in humans and is commonly used in music composition. Why clock synchronization is unusual in some species and the mechanism that determines optimal tempo is unclear.
Here we examined physical movements and neural activity in rats to determine their shock sensitivity.
Close examination of head movements and neural recordings revealed that rats showed clear beat synchronization and auditory cortex activity within 120 to 140 BPM. Mathematical modeling suggests that short-term adjustment underlies this beat tuning.
Our results support the hypothesis that the optimal tempo for beat synchronization is determined by the time constant of neuronal dynamics, which is conserved across species, and not by the species-specific time constant of physical movements. Thus, the latent neural propensity for auditory motor capture may provide a basis for human capture that is much more widespread than currently thought.
Further studies comparing humans and animals will provide insights into the origins of music and dance.