It has long been known that Ludwig van Beethoven composed music after he became deaf. Now neuroscience research is revealing how Beethoven was able to “hear” the notes of his symphony, at least in his own head, even though he couldn’t hear the music being played on stage or the applause that followed.
Robert J. Zatorre, a neuroscientist at the Montreal Neurological Institute and a leading researcher in the field of auditory imagery, refers to the phenomenon of imagined music as “mental concerts.” We often experience our own mental concert when we recall a favorite song, or when we are unable to get an annoying advertising jingle out of our heads.
But Zatorre’s research has broader implications. “Music provides a window into the mind, because it encompasses so many different mental functions, from emotion to memory to perception,” Zatorre says. “It’s a very basic human function that’s interesting because it gives us insight into the mysterious internal world of the mind.”
A Brain Workout
How mental concerts play out remained a mystery until the past decade, when advanced brain imaging techniques such as positron emission tomography and functional magnetic resonance imaging made it possible to peer into the brain and see what areas are activated when people see, hear, and imagine things.
In a July 2005 Neuron paper reviewing the research on auditory imaging, Zatorre and colleague Andrea Halpern, a psychologist at Bucknell University, conclude that people imagine music in much the same way that they hear it: through activation of the auditory cortex.
“If you make a noise, nerve cells in the auditory cortex become active,” Zatorre says. “If you ask people to imagine music, portions of that circuit become active. So this suggests that when you experience internal music, it’s mediated by the same part of the brain that carries sound. That tells us something about how this type of consciousness is mediated in the brain.”
The findings about auditory imagery parallel those about the brain basis of visual and motor imagery. To summarize years of research simply: Imagine how the ocean looks at dawn, and you are activating much the same areas of your visual cortex as if you were actually seeing the sun rise over water. Think about walking on a beach, and you activate the same areas of the motor cortex as if you were actually strolling on the sand.
Data from functional magnetic resonance imaging, superimposed on a 3-D view of the brain, show activity in the auditory cortex of the right temporal lobe. This area is active when people listen to complex musical patterns.Courtesy of Dr. Robert J. Zatorre, Montreal Neurological Institute
“It’s clear that when we imagine something we use the same part of the brain as if we were really seeing or hearing it,” says Michael Gazzaniga, a cognitive neuroscientist at Dartmouth. “This indicates that thinking is hard work, and you’re really giving your brain a workout when you imagine something.”
Physical and Mental Practice
Several studies indicate that musical practice builds certain areas of the brain, at least in professional musicians.
Most of these studies have focused on changes in “gray matter,” or nerve cells, of the brain. But in the September 2005 issue of Nature Neuroscience, Frederik Ullén and colleagues from the Karolinska Institute in Sweden report evidence of increased white matter— which is made up of myelin, the fatty white insulation around axons that helps brain cells to communicate—in the brains of concert pianists.
Research has shown that myelination is stimulated as nerve cells communicate for the first time, as they would when someone is learning a new skill. It also is known that as particular areas of the brain become better myelinated, certain abilities—such as working memory, reading skills, and the development of fine finger movement— improve. It would follow, then, that concert pianists should have more white matter in certain areas of the brain than the rest of us.
To find out, the researchers used a new type of magnetic resonance imaging technique, known as diffusion tensor imaging, to compare white matter organization in the brains of eight professional concert pianists and a similar group of nonmusicians. They also asked the pianists at what age they began practicing and to estimate how many hours they had practiced over their lifetimes.
Ullén and his team found that the pianists who had practiced the most also had the greatest amount of white matter in areas of their brains associated with piano playing. The researchers speculate that this increased myelination occurred as activated nerve cells formed connections with others during practice. What’s more, pianists who began practicing as children experienced white matter growth in more brain areas than did nonmusicians or pianists who started training later.
Many musicians also use mental workouts to practice. In their Neuron review, Zatorre and Halpern present evidence that such mental workouts may also pay dividends. For example, Alvaro Pascual-Leone, a neurologist at Harvard, has demonstrated that mental practice helps improve musical performance, although not as much as actual practice.
There is also some evidence that musicians activate both the auditory and motor sections of the cortex during mental practice, indicating that auditory and motor imagery may be linked—at least in professional musicians. Zatorre and Halpern mention one study that showed that as pianists listen to pieces they knew how to perform, they activate areas in the motor cortex that corresponded to the finger movements they would have to make in order to produce the sounds—even though they weren’t actually moving their fingers. Another study reported that pianists who watch a silent movie of someone playing a piano nevertheless activate the auditory cortex—hearing the music even in the absence of sound.
From Imagining to Creating
Questions about auditory imaging remain, chief among them how mental concerts are generated in the first place. Zatorre thinks the process probably involves interactions between memory systems and the auditory cortex.
“If you recall music, it was somehow stored, you retrieve it, and then send it to the auditory cortex to imagine it,” Zatorre says. “But we don’t know exactly how this process works.”
Yet the research on mental concerts and other types of auditory imagery is already providing insight into consciousness and even creativity. Take Beethoven’s ability to compose after he could no longer hear.
“This shows the degree to which some people can not only generate internal sounds, based on what they’ve heard, but also create new ones,” Zatorre says.
“Zatorre’s work adds an interesting dimension to what we’re learning from others about things like cognition and consciousness,” Gazzaniga says. “He’s using music to probe at fundamental questions of what makes us human.”