By Carl Sherman
At 12, Ileana was a lively girl who loved sports and ballet. Then an arteriovenous malformation—an undetected circulatory defect —bled into her spinal cord and put her in a wheelchair. Years of physical therapy enabled her to walk enough to prevent atrophy. But a halting, unstable gait meant constant danger of falling.
She needed to move better, for safety’s sake. Now 18, Ileana wanted other things, too— to participate in her high school graduation. To dance at her senior prom.
So she turned to music therapy.
Putting music to therapeutic use dates back to at least World War II, when musicians played at veterans’ hospitals to boost morale and lift spirits. Techniques were refined in the decades that followed, but it was only in recent years that brain research established a solid scientific basis for neurologic music therapy (NMT)—the use of music and musical elements such as rhythm and melody to rehabilitate function lost through central nervous system injury or disease.
“The development of technology like brain wave analysis and brain imaging in the 1990s completely transformed NMT, allowing us to see how the brain is involved in musical experience,” says Shannon K. de l’Etoile, program director of music therapy at the University of Miami, who worked with Ileana. “This has enabled us to apply therapy more systematically, and to know what to expect.”
The restorative power of music lies in its robust effects on diverse regions of the brain, says Michael Thaut, scientific director for the Center for Biomedical Research in Music at Colorado State University. “A lot of the systems that music engages also share a variety of other functions—verbal language, motor control, attention, memory, decision making, pattern perception.
“With specifically designed music exercises we can access the structure and function of these brain systems, and make changes that have measurable behavioral outcomes.”
Rhythms of life
One of the best established of these exercises, rhythmic auditory stimulation (RAS), grew from the observation that people naturally move to a musical beat. “The external rhythm drives and entrains the internal timekeeper for motor functions,” is how de l’Etoile describes it.
Therapists use RAS to help people with central nervous system injuries and movement disorders such as Parkinson’s disease stabilize and improve rhythmic, repetitive behavior such as walking. De l’Etoile chose this technique for Ileana.
When she observed the girl and matched a rhythm to her pace, “Ileana started to walk and didn’t stop,” de l’Etoile says. In subsequent sessions, de l’Etoile sped up the rhythm, and Ileana’s pace accelerated accordingly. After a brief course of treatment, she was taking 17 percent more steps per minute.
Music therapy didn’t restore Ileana’s ability to walk normally—quite possibly, nothing ever would. But with its help, she could proudly cross the stage to receive her diploma—and dance at her senior prom.
“We knew that [RAS] worked before we knew how it worked,” Thaut says. Since then, “we’ve learned there is basic connectivity between the auditory and motor systems in the brain, which we can measure with brain imaging.” Such links have been shown at cortical, midbrain, and thalamus levels, he says.
Thaut’s research helped inspire Joyce L. Chen, then working as a physical therapist, to delve beneath the surface of neurorehabilitation. In subsequent doctoral studies with Robert J. Zatorre, co-director of the International Laboratory for Brain, Music, and Sound Research in Montreal, her goal was “to understand the basic science behind auditory-motor entrainment,” she says. “We tried to refine existing studies, to look at what specific brain regions are integrating sensory information and what might facilitate the process.”
Chen’s studies pinpointed such areas in the higher brain, Zatorre says: “As meter emerged from a homogenous sequence of tones, we could see increased communication between auditory and motor regions.” Functional MRI (fMRI) scans showed that a stronger musical beat intensified the interaction between the auditory cortex and the premotor cortex.
Having volunteers tap along with the music produced activity in a broad area of the premotor cortex, while anticipating they’d reproduce the rhythm later activated a more limited portion. Just listening to the music, without planning to tap, activated some of the areas as well.
“This confirms that the auditory and motor systems are tightly coupled, even when we aren’t moving,” Zatorre says.
Now a postdoctoral researcher at Oxford University, Chen is examining these anatomical connections more closely, and hopes, ultimately, to tie the science to work with patients.
Connections between other brain regions explain how NMT helps stroke victims regain the power of speech. “For more than 100 years, there have been anecdotal reports of patients who were unable to talk but could sing,” says Gottfried Schlaug, director of Harvard’s Music and Neuroimaging Laboratory and a Dana Foundation grantee. “That observation led to a clinical intervention.”
Melodic intonation therapy (MIT) is for people with “nonfluent aphasia”— they understand words, but can’t talk—a condition that reflects damage, typically by a stroke, to the left brain area essential for the complex coordination of breath and musculature that produces speech. In each session, the patient “sings” phrases and sentences while tapping with their unaffected hand.
Intensive work with MIT—70 to 80 sessions over a period of several weeks is typical— substantially improves speech in many cases, but the mechanism is unclear. “No one had looked at the neurocorrelates—which regions of the brain respond and are changed in therapy,” Schlaug says. Evidence points toward the right hemisphere, “which seems more adept in dealing with stimuli that have a contour,” he says. From the architecture of a melodic sentence or phrase, this part of the brain creates “a scaffold on which the words can be placed.”
His lab focused on the arcuate fasciculus (AF), a bundle of axons connecting brain regions that hear and comprehend with those that issues motor commands producing speech. “We felt that if the patient is learning to map sounds to action, it has to involve the AF,” Schlaug says.
His study found significant speech improvement and substantial brain changes—greater right AF volume and more white matter fibers—in all six patients investigated after treatment. In one patient, the fibers grew longer as well. Although it did not reach statistical significance (due to the small numbers involved, Schlaug suggests), the association between clinical and neuroanatomical change supports a link between the degree of speech improvement and the number of additional fibers.
Normal development, Schlaug says, leaves the right side of the AF with too few fibers to permit corresponding right hemisphere structures to take over when left-sided speech centers are damaged. MIT, he conjectured, restarts development in this area, thickening the right AF enough to re-create the loop between brain functions critical for communication.
Most recently, neurologic music therapists have taken on the challenge of cognitive rehabilitation. Inspired by the success of techniques such as RAS, Thaut and others have enlisted music to retrain attention, memory, and executive functions, for example,planning, organizing, and carrying out intentions.
For one exercise, “we create improvisational composition games for the patient,” Thaut says. “We present a bunch of rhythm tracks for him to choose from. We ask how the melody should sound [and] we guide the patient in building a musical composition, a highly involved process that engages the prefrontal cortex systems used in executive function.” In one study, 31 brain-injured individuals improved significantly more than untreated patients in a test of executive function after only one session of this kind of therapy.
Other research suggests how the brain changes to promote cognitive improvement. The power of music to aid memory is well known—think of the “alphabet song” children use to remember their letters. In theory, Thaut says, the structure of melody creates a template that organizes information in memorable chunks.
Work in his lab showed such organization on the neural level: Brain waves were more highly synchronized when subjects learned a word list set to music than when they learned the words alone. This increased synchronization accompanied superior memory performance both in healthy people and in those with multiple sclerosis, where cognitive deficits are common.
In recent years, there has been “a lot of give and take” between neuroscience and neurologic music therapists—a kind of dance between experimental findings, theoretical models, and pragmatic applications, Thaut says.
Schlaug’s research, for example, grew out of a well-established clinical technique, melodic intonation therapy, that his findings may in turn refine. Tracking neuroanatomical changes, he says, “will allow us to fine-tune MIT and better target the areas in the brain that are actually changing.”