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A Musical Brain May Help Us Understand Language And Appreciate Tchaikovsky

Jun 10, 2019
Originally published on June 13, 2019 3:41 pm

What sounds like music to us may just be noise to a macaque monkey.

That's because a monkey's brain appears to lack critical circuits that are highly sensitive to a sound's pitch, a team reported Monday in the journal Nature Neuroscience.

The finding suggests that humans may have developed brain areas that are sensitive to pitch and tone in order to process the sounds associated with speech and music.

"The macaque monkey doesn't have the hardware," says Bevil Conway, an investigator at the National Institutes of Health. "The question in my mind is, what are the monkeys hearing when they listen to Tchaikovsky's Fifth Symphony?"

The study began with a bet between Conway and Sam Norman-Haignere, who was a graduate student at the time.

Norman-Haignere, who is now a postdoctoral researcher at Columbia University, was part of a team that found evidence that the human brain responds to a sound's pitch.

"I was like, well if you see that and it's a robust finding you see in humans, we'll see it in monkeys," Conway says.

But Norman-Haignere thought monkey brains might be different.

"Honestly, I wasn't sure," Norman-Haignere says. "I mean that's usually a sign of a good experiment, you know, when you don't know what the outcome is."

So the two scientists and several colleagues used a special type of MRI to monitor the brains of six people and five macaque monkeys as they listened to a range of sounds through headphones.

Some of the sounds were more like music, where changes in pitch are obvious.

Other sounds were more like noise.

And Conway says it didn't take long to realize he'd lost his bet.

"In humans you see this beautiful organization, pitch bias, and it's clear as day," Conway says. In monkeys, he says, "we see nothing."

That surprised Conway because his own research had shown that the two species are nearly identical when it comes to processing visual information.

"When I look at something, I'm pretty sure that the monkey is seeing the same thing that I'm seeing," he says. "But here in the auditory domain it seems fundamentally different."

The study didn't try to explain why sounds would be processed differently in a human brain. But one possibility involves our exposure to speech and music.

"Both speech and music are highly complex structured sounds," Norman-Haignere says, "and it's totally plausible that the brain has developed regions that are highly tuned to those structures."

That tuning could be the result of "something in our genetic code that causes those regions to develop the way they are and to be located where they are," Norman-Haignere says.

Or, he says, it could be that these brain regions develop as children listen to music and speech.

Regardless, subtle changes in pitch and tone seem to be critical when people want to convey emotion," Conway says.

"You can know whether or not I'm angry or sad or questioning or confused, and you can get almost all of that meaning just from the tone," he says.

Copyright 2019 NPR. To see more, visit https://www.npr.org.

MARY LOUISE KELLY, HOST:

When a person listens to Tchaikovsky's Fifth Symphony, it sounds like this.

(SOUNDBITE OF ORCHESTRE PHILHARMONIQUE D'OSLO PERFORMANCE OF "SYMPHONIE NO. 5 EN MI MINUER, OP. 64: I. ANDANTE-ALLEGRO CON ANIMA")

KELLY: But to a monkey, that symphony may sound more like this.

(SOUNDBITE OF MUSIC)

KELLY: That's one finding from a study that compared the way human and monkey brains process sounds. NPR's Jon Hamilton reports the research may help explain why people are able to appreciate music and understand speech.

JON HAMILTON, BYLINE: The study began with a bet between two scientists. One of them is Bevil Conway, a researcher at the National Institutes of Health. And one day, Conway was talking to a graduate student who'd done research showing that the human brain is very attuned to a sound's pitch.

BEVIL CONWAY: I was like, well, if you see that and it's a robust finding you see in humans, we'll see it in monkeys.

HAMILTON: But Sam Norman-Haignere, who is now a postdoc at Columbia University, thought monkey brains might be different.

SAM NORMAN-HAIGNERE: Honestly, I wasn't sure. I mean, that's usually a sign of a good experiment, you know, when you don't know what the outcome is.

HAMILTON: So the two scientists and some colleagues did that experiment. They used a special type of MRI to monitor the brains of six people and five macaque monkeys as they listened to a range of sounds. Some of the sounds were more like music, where changes in pitch are obvious.

(SOUNDBITE OF MUSIC)

HAMILTON: Some were more like noise.

(SOUNDBITE OF MUSIC)

HAMILTON: And Conway says it didn't take long to realize he'd lost his bet.

CONWAY: In humans, you see this beautiful organization - pitch bias. And it's clear as day in a single scan. And the drum-roll question was, what do we see in monkeys? And there, we see nothing.

HAMILTON: The study, which appears in the journal Nature Neuroscience, found that monkey brains just weren't that sensitive to pitch. And Conway says that surprised him because his research had shown that the two species are nearly identical when it comes to processing visual information.

CONWAY: When I look at something, I'm pretty sure that the monkey is seeing the same thing that I'm seeing. But here in the auditory domain, it seems fundamentally different.

HAMILTON: But why? Norman-Haignere says one answer may be our exposure to speech and music.

NORMAN-HAIGNERE: Both speech and music are highly complex, structured sounds. And it's totally plausible that the brain has developed regions that are highly tuned to those structures.

HAMILTON: Norman-Haignere says that tuning could be something we're born with.

NORMAN-HAIGNERE: It's plausible that there's something in our genetic code that causes those regions to develop the way they are and to be located where they are.

HAMILTON: Or it could be that these brain regions develop as children listen to music and speech. Conway says, regardless, subtle changes in pitch and tone seem to be critical when people want to convey emotion.

CONWAY: You can know whether or not I'm angry or sad or questioning or confused. And you can get almost all of that meaning just from the tone.

HAMILTON: So Conway says it makes sense that music can also convey emotion even when it doesn't include any words. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.