Blame That Tune

11 June 2008 (All day)

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Sour note? Tune-deaf people can't tell the difference between a well-played and a poorly played song.

Can't stand today's music? Neither can tune-deaf people. In fact, the disorder makes listening to any music unenjoyable, because the brain can't organize the sounds into a comprehensible melody. New research indicates that the problem lies somewhere in the conscious mind: The brains of tune-deaf individuals know when a sour note has been played, but the people themselves are unaware of it.

Two percent to 4% of the U.S. population is tune deaf. People with the disorder, also known as tone deafness, have trouble telling the difference between a good melody and a bad one. Tune deafness is highly heritable, yet biologists know little about what goes wrong in the brain. The normal process of detecting bad notes has been much better described: A device that measures brain activity, called an electroencephalograph, registers two signals, known as mismatch negativity (MMN) and P300.

Neuroscientist Allen Braun and colleagues at the U.S. National Institute on Deafness and Other Communication Disorders in Bethesda, Maryland, wondered if the same signals would turn up in the brains of tune-deaf people as they listened to a botched melody. The researchers had seven tune-deaf and 10 non-tune-deaf people listen to a variety of familiar tunes such as "Mary Had a Little Lamb" and "The Star-Spangled Banner" while an electroencephalograph measured their brain activity. As expected, these subjects did not have the typical MMN response to poorly played tunes, the team reports today in PLoS One. But to their surprise, the researchers did detect the P300 response to the incorrect notes. Braun believes these results show that the brain can detect the differences even though tune-deaf people aren't aware.

Neuroscientist Isabelle Peretz of the University of Montreal in Canada agrees. She has come to the same conclusion after conducting a similar, unpublished study. Bottom line: Tune-deaf people can tell, at least on a subconscious level, that a poorly played "Happy Birthday" just doesn't sound quite right.

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