New Research Sheds Light on Tone-Deafness
In the August 19 issue of The Journal of Neuroscience, Psyche Loui, PhD, a researcher in the Music and Neuroimaging Laboratory at BIDMC, together with lab director
Gottfried Schlaug, MD, PhD, and imaging scientist
David Alsop, PhD, describe new research that shows a missing brain circuit among people who are tone deaf, offering the first clear explanation for why some people can't carry a tune. We asked Loui about her research findings.
What is tone deafness?
People who are truly tone deaf can't pick out differences in pitch or follow even the simplest of tunes. The technical term for tone deafness is amusia and it affects anywhere from four to 17 percent of the population.
Are all bad singers tone deaf?
No. Lots of people with poor singing voices can hear music just fine - they just can't produce it. That's the difference - a person who is tone deaf can't discern different pitches or musical tunes - they're not hearing the same thing that you and I are hearing.
So, tone deafness doesn't actually imply an inability to hear?
No. People who are tone deaf have normal hearing and speech, and conversely, people can be hard of hearing but still have music in their minds. Beethoven, for example, was completely deaf late in his life, but was able to compose some of our greatest classical music pieces.
What did your study find?
It turns out that individuals who are tone deaf have a problem with brain connections; a "wiring problem," you might say. The brain pathway that connects the perception and motor areas of the brain - known as the arcuate fasciculus - has fewer connections among people who are tone deaf. Although the arcuate fasciculus was previously known to have a role in language processes, this was the first time it was shown that the AF also has a role in non-linguistic functions (that being singing).
How did you conduct this research?
We did diffusion tensor imaging, which is a kind of MRI, on 20 people, half of whom were tone deaf. The imaging showed that the tone-deaf individuals had fewer fiber tract connections between the frontal and temporal regions of the brain. In some cases, we couldn't see any fibers at all. If you think of the nerve connections as being like a highway, in tone-deaf people, there's a lot less traffic traveling on the roadway than there is in people with normal musical abilities.
Do your findings have broader implications for speech and language?
Yes. Now that we know which brain connections are at stake, we hope that a future intervention for tone-deafness will also benefit people who have dyslexia, stuttering or other developmental speech and language disorders.
How can a person know if he or she is truly tone deaf - or is just a lousy singer?
We are hosting a test at
www.musicianbrain.com that you can take to determine whether or not you are tone-deaf. The test entails listening to two different tones, and then deciding which one is higher. The test starts out pretty easy, with pitches being very far apart; then it gets harder, until you can't tell the difference anymore, and it records the
threshold at which you can just barely detect pitch differences. If your enter your e-mail address on the website, we can e-mail you the test results within a week or so.
Do you sing?
I do sing, but not professionally. I do, however, play the violin, and am a member of the Longwood Symphony Orchestra. We are a group of medical professionals from the Boston area who perform together four times a year for charity and to raise awareness and raise funds for medical research. We also play very interesting pieces at great venues; at our last concert, we played "Star Trek" on the Boston Esplanade and drew a crowd of 9,000 concert-goers!
www.musicianbrain.com to learn more.