WASHINGTON -- Jazz musicians are famous for their musical conversations -- one improvises a few bars and another plays an answer. Now research shows some of the brain's language regions enable that musical back-and-forth much like a spoken conversation.

It gives new meaning to the idea of music as a universal language.

The finding, published Wednesday in the journal PLoS One, is the latest in the growing field of musical neuroscience: Researchers are using how we play and hear music to illuminate different ways that the brain works.

And to Dr. Charles Limb, a saxophonist-turned-hearing specialist at Johns Hopkins University, the spontaneity that is a hallmark of jazz offered a rare chance to compare music and language.

"They appear to be talking to one another through their instruments," Limb explained. "What happens when you have a musical conversation?"

Watching brains on jazz requires getting musicians to lie flat inside a cramped MRI scanner that measures changes in oxygen use by different parts of the brain as they play.

An MRI machine contains a giant magnet -- meaning no trumpet or sax. So Limb had a special metal-free keyboard manufactured, and then recruited 11 experienced jazz pianists to play it inside the scanner. They watched their fingers through strategically placed mirrors during 10-minute music stretches.

Sometimes they played scales. Other times, they did what's called "trading fours," where the pianist made up four bars, and then Limb or another musician-scientist in the lab improvised four bars in return, and the pianist responded with still new notes.

That conversation-like improvisation activated brain areas that normally process the syntax of language, the way that words are put together into phrases and sentences. Even between their turns playing, the brain wasn't resting. The musicians were processing what they were hearing to come up with new sounds that were a good fit.

At the same time, certain other regions of the brain involved with language -- those that process the meaning of words -- were tuned down, Limb found.

That makes sense because "the richness of the structure of music is what gives it its significance," Limb said. "You can have substantive discourse using music, without any words, yet language areas of the brain are involved in this unique way."

One ultimate goal of musical neuroscience is to better understand the brain's circuitry, and how it can rewire itself, in hopes of eventually finding new treatments for neural disorders. Limb made headlines several years ago when he measured jazz musicians' riffs -- longer, solo improvisations -- to study creativity in the brain.

"We know nothing about how the brain innovates," he said. "This is one way to learn what innovation means neurologically."

Stay tuned: Next he hopes to study children who are just learning music, and to compare amateurs to professionals, as he explores how people become creative.