Tone-deaf are wired wrong

Do your friends cover their ears when you sing along with the radio? Does the choir director ask you to lip-sync? If you're one of the unlucky people who is tone-deaf, it turns out your brain may have a wiring problem. That's what new research suggests.

People who are tone-deaf can't detect differences in musical pitch but usually have normal hearing and speech. Tone-deafness runs in families, and estimates of how many people have the problem range from 4% to 17%.

In the small study done in Boston, brain scans showed there was a difference in a particular brain circuit between those who were tone-deaf and those who weren't.

Among the tone-deaf, researchers discovered there were fewer connections between two areas of the brain that perceive and produce sounds.

The study's lead author, Psyche Loui, likened the connection to a highway between two islands in the brain.

In tone-deaf people, "there's less traffic on the highway," said Loui, who studies music and the brain at Harvard Medical School and is also a musician.

How the study was done
Loui and her colleagues took brain scans of 20 people, half of them tone-deaf. Those who were tone-deaf had fewer nerve fibres between the frontal and temporal regions of the brain, or in some cases the fibres couldn't be detected at all. The researchers reported their the Journal of Neuroscience.

"It's a new piece in our understanding of tone-deafness and the processes that are involved in the perception of pitch in general," said Nina Kraus of North-western University, who wasn't involved in the research.

Loui said the brain connection they examined was long known to be involved in language. "Now that we know which brain pathways to train," she said, there may be ways to help people with tone-deafness, and perhaps those with other language disorders. – (Sapa, August 2009)