Playing Music To Baby Mice Shapes Their Brain Development In A Sex-Specific Way

The researchers, based at the Hebrew University of Jerusalem, exposed litters of baby mice to three different sound conditions. Some were kept in silence; some were exposed to chirping noises; and the lucky remaining few had their cultural horizons broadened by the incomparable Ludwig van Beethoven and the first movement of his Ninth Symphony. 

Exposure sessions continued between day 7 and day 40 post-birth, and there was also a control group who were housed in similar conditions but not brought to the lab for their daily sound treatment. 

If you’re still not totally sold on this “mice enjoying a bit of Beethoven” thing, we’re here to tell you that this is not the first study to investigate these ideas. 

“When Kamini [Sehrawat], the student who ran this project, showed me a paper that actually tested mouse sound preferences, I thought it’s worthwhile trying to do that too,” senior author Professor Israel Nelken told IFLScience. Nelken’s previous work has been more focused on the mechanics of the brain’s auditory system, whereas others have studied preferences from a more emotional angle. “So,” he explained, “I thought we can give our special point of view into this field.”

When you do science, you throw a question to nature and nature provides answers, but not necessarily to the question you asked.

Professor Israel Nelken

When the mice were revisited as adults, Sehrawat and Nelken saw how their early sound exposures were still impacting their behavior. What they didn’t expect, however, was that there was a clear difference between the male and female mice. 

“Very often, behavioral work is done in males and not females,” Nelken explained. 

This lack of inclusion of females in research is something that reaches into many fields; from the study of animal behavior to evolutionary biology, science has long had a male bias problem. Only this year, for instance, scientists discovered female same-sex behaviors in Hawaiian field crickets for the first time – but only because no one had thought to look before.  

The bias extends into human medical research too, which is thought to contribute to gender gaps in care and a poorer understanding of health issues affecting female bodies.   

For their study, however, Sehrawat and Nelken weren’t able to perform the usual step of excluding female subjects. 

“We just tested everyone, all the pups that we had,” Nelken told IFLScience. They were keen to minimize the number of animals they used as far as possible, and didn’t think sex would be a major factor. The idea of a sex difference wasn’t even on their minds when they generated their initial hypothesis. But as soon as they started analyzing the data, it became clear they’d have to think again.

“When you do science, you throw a question to nature and nature provides answers, but not necessarily to the question you asked.”

The male mice showed an avoidance of novel sounds as adults – those that had been exposed to music as infants showed varied preferences, while those that had been exposed only to silence or non-musical sounds strongly avoided music. 

In the females, there seemed to be less of a strong effect. The adults showed more varied sound preferences, irrespective of what study group they had been in. 

When Sehrawat and Nelken looked inside the mice’s brains using calcium imaging, they found that stronger activity in the auditory cortex was linked to less of a preference for music. In the males there didn’t seem to be the same connection between behavior and auditory cortex activity, meaning something else is going on. 

Rodents and humans – we are certainly not the same!

Professor Israel Nelken

That “something” has been the subject of further experiments in Nelken’s lab. 

“The experiments that we are currently doing and preparing for publication [led us to] test what’s happening in the main forebrain. The area that releases dopamine into the forebrain in rodents [is] called the VTA, the ventral tegmental area.”

Dopamine, Nelken summarized, is “sex, drugs, and rock and roll.”

“Everything that’s good is associated with dopamine release,” he told IFLScience, “and it turns out that music is too. So, the rock and roll is really there!”

Some of their preliminary results suggest that there could be an association between dopaminergic signaling and sound preferences in the male mice, but it’s still very early days. 

“I’m not sure that Beethoven would be my first choice”

There was one burning question we had to ask: why Beethoven? Sadly, it’s not because something in the great master’s work particularly speaks to the rodent psyche.

“Previous people doing this type of experiment used Beethoven’s Ninth, and we wanted [to] try to reproduce the previous results. So, we used part of the Ninth, and it stuck.”

By this point, we’d heard a lot about mice and their musical taste; but it would have been remiss of us not to ask whether these results might extend to humans too. 

“Rodents and humans – we are certainly not the same!” Nelken reminded us. There’s some evidence that human music preferences are shaped in early life, with research suggesting that we stick to music we already know and become less exploratory as we get older. But it’s really too early to say from this study whether there are any similar mechanisms at play in both rodents and humans. 

It’s also difficult to speculate about how these effects might play out if we were to look at, say, vision instead of hearing, because the type of information we receive from our ears and eyes is so different. 

So, before you go and buy up the entirety of Beethoven’s back catalog to play to your kids, maybe pause for a second. Nelken stressed that it’s way too soon to infer anything about how human sensory experiences are shaped by our early listening, and whether there are sex differences there, too. 

“I think in general it’s good for children to be exposed to music,” he conceded, but “I am not sure Beethoven would be my first choice.” Certainly, Nelken’s own grandchildren weren’t overly enamored with the Ninth Symphony – apparently, they preferred Mozart. 

“I wouldn’t try to read too much into what we should do beyond the mere fact that we know that children are highly plastic. They learn, they change. Whatever you do with them will change them. So be respectful.”

Sound advice. And just a final note from this author: if you are planning to give Beethoven’s Ninth a go, as a singer, might I humbly suggest skipping straight to the final movement? Thank me later. 

The study is published in the journal Cell Reports.