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A soundtrack for the body

Musician and Beth Israel neuroscientist Amir Lahav is working to rehabilitate stroke patients by turning their bodies into musical instruments.

Constanza Villalba

During his years as a professional musician and composer, Amir Lahav knew that music had a profound effect on the brain. Still, it wasn’t until he became a neuroscientist that he began to understand exactly how music and brain function are intertwined. Now, Lahav, a neurology researcher at Beth Israel Deaconess Medical Center, is applying that knowledge to develop a device that uses music to help stroke patients regain control of their movements.

Neuroscientist Amir Lahav uses his musical talents to study how music can help with motor learning. (Credit: Heather Kraft)

In 2006, the same organization that hands out the Grammy Awards gave Lahav $40,000 to develop the machine, called an interactive auditory feedback device. It consists of cameras and a computer that “senses” a person’s movements and converts those movements into sound. Unpublished results from early tests on five stroke patients show that patients using the device appear to recover better motor control than those undergoing traditional physical therapy alone.

At the heart of the device is software that recognizes when a patient is doing a certain movement correctly. When a patient moves correctly (for example, fully extending the wrist), the device rewards him by playing parts of a familiar song, such as “Hey Jude” or “Hotel California.” If the movement isn’t done properly (only partly extending the wrist), the device plays a distorted version of the song. The patient is able to control how the song sounds based on how he moves.

If this sounds like music therapy, think again. Lahav’s approach is about “moving to make music,” says Lahav, not about “moving to music.” It’s an important distinction. Lahav says that using body movements to control music is the key to tapping into a subset of brain cells, called mirror neurons, which may be able to improve motor learning without the need for extra physical training.

Monkey hear, monkey do

The mirror neuron system is a set of brain cells that become active both when an animal performs an action and when the animal watches another animal perform the same action. The discovery of the system was groundbreaking, because it suggests a mechanism for how animals learn through imitation and for how animals understand the actions of others.

Lahav became interested in the mirror neuron system when a group of researchers from the University of Parma in Italy showed in 2002 that mirror neurons respond not only to the sight of actions, but also to their sounds. A subgroup of mirror neurons in monkeys, for instance, fire not just when monkeys see other monkeys breaking open a peanut, but also when they hear the sound of the peanut breaking.

Drawing on his musical background, Lahav hypothesized that mirror neurons in humans are at work when a person hears a piece of music that he or she knows how to perform.

“From my own experience, if there was a piece of music that I played, that I was really good at,” says Lahav, “every time I heard this piece I almost felt as if my fingers had their own will…. I felt as though I was rehearsing the music in my mind.”

Music and movement merge

To test whether music could become synonymous with action in the brain, Lahav orchestrated a study in which he taught several nonmusicians to play a piece of piano music, which Lahav composed. Then Lahav and his colleagues imaged the brains of the subjects while they lay still and listened to three pieces of music: the rehearsed one, one they had heard before but had not rehearsed, and a third one containing the same notes as the rehearsed piece, but in a jumbled order.

Lahav and his team found that the areas of the subjects’ brains involved in motor output (presumably including mirror neurons) became active when subjects listened to the rehearsed piece but not when they listened to the other familiar music. The jumbled version of the rehearsed piece also produced some motor-related activation but not to the same degree as the intact piece.

Lahav took this experiment a step further by demonstrating, in unpublished results, that merely listening to the rehearsed music improves the subjects’ ability to play it later on, even if they did not practice it again. He suspects that the sound of the music prompts the brain to “practice,” even if the fingers aren’t moving.

Music machine

This is where the auditory feedback device comes in. Since hearing the sounds associated with an action appears to improve the execution of that action, Lahav thought this mode of learning could be applied to people with motor deficits. Stroke survivors, however, often cannot perform even the most basic motor tasks; teaching them to do an activity as complex as playing an instrument was out of the question.

So Lahav designed his auditory feedback device to “musicalize” even the subtlest of movements. Early tests suggest that the musical reward helps patients using the device along with traditional physical therapy to outperform those doing physical therapy alone. The next step is to see whether hearing a song that a patient associates with a particular action—say, zipping up a jacket—improves the patient’s ability to perform that activity without practice. Even if such a device did work though, it wouldn’t replace physical therapy; it would just be another tool for physical therapists to use.

Mirror-neuron expert Marco Iacoboni, an associate professor of psychiatry and biobehavioral sciences at the University of California, Los Angeles, says Lahav’s experiments are very clever. But, he adds, “even if the treatment works, we can’t say for sure it works because of mirror neurons, although that would be a reasonable guess.”

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