Science Takes Note of Tone-Deafness

For the first time, links between brain activity and inability to recognize pitch

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By Amanda Gardner
HealthDay Reporter

FRIDAY, Sept. 9, 2005 (HealthDay News) -- By tuning in to brain activity patterns, researchers say they've finally been able to identify part of what goes wrong in the brains of people who are tone deaf.

According to a study appearing in the current issue of Annals of Neurology, people with amusia, the scientific term for tone deafness, have abnormal activity in the right side of the brain.

"This study is unique in that it does suggest a brain mechanism that may explain why adults with congenital amusia perceive pitch differently than controls," said Julene K. Johnson, an assistant professor of neurology at the University of California San Francisco Memory and Aging Center.

Although she was not involved in the research, Johnson believes the finding "may help direct future studies to determine where the abnormalities may be in the brain and how individuals with congenital amusia might benefit from rehabilitation at an early age (similar to dyslexia)."

According to the study -- which was conducted by researchers in Canada and Finland -- some 4 percent of people suffer from congenital amusia, or tone deafness present since birth. As a result, they are unable to enjoy music in the way ordinary people do.

Because amusia is related to speech and reading disorders such as dyslexia, the findings may have implications not only for tone deafness, but for speech learning as well, experts say.

"It's entirely possible if a person has disability in the neural structure where they cannot process the nuances of tone, not only might they have difficulty with pitch perception and musical appreciation, but they also might have difficulty with vowel perception, which then relates to reading," explained Roy Sullivan, who is both a musician and an audiologist with Mercy Medical Center in Rockville Center, N.Y.

His wife, Carol Sullivan, is a speech language pathologist in Garden City, N.Y. She added that, "having an ability to discern the acoustic contours in speech assists the listener in extracting the intent of speech. The ability to interpret the intent of the message can truly negatively affect relationships throughout a person's life."

In the Canadian/Finnish study, researchers led by Isabelle Peretz at the University of Montreal assessed how brain cells in different regions of the brain responded to tones using electroencephalography (EEG).

Eight tone deaf individuals and 10 matched control subjects listened to sequences of different tones, all 100 milliseconds long played at a particular pitch level. Participants were asked to press a "yes" button when they detected a change and a "no" button when they did not. They were also asked to blink at the end of each tone sequence.

People who were tone deaf had difficulty distinguishing small pitch changes, although not large ones. The people with amusia also showed abnormal brain activity in the right half of the brain.

"The study also suggests that the primary auditory cortex is intact in congenital amusia and that the difficulty with pitch perception may occur later in the auditory processing stream (outside of the primary auditory cortex)," Johnson added.

All of this information may contribute to how hearing, speech and reading issues are diagnosed and treated.

"This is science that comes back to the schools," Carol Sullivan said. "For the first time, studies of the brain's neurological functioning are telling us a lot of information about differences among students and about how they learn and how they can hear. Functional MRIs are giving us a rich database on how brains function while we read."

This data lends a window into potential therapeutic options and on how different therapies actually affect the brain, she said.

More information

Learn more about dyslexia from the International Dyslexia Association.

SOURCES: Julene K. Johnson, Ph.D., assistant professor, neurology, University of California San Francisco Memory and Aging Center; Roy Sullivan, Ph.D., audiologist, Mercy Medical Center, Rockville Center, N.Y.; Carol A. Sullivan, MS, speech language pathologist, Garden City, N.Y.; Aug. 29, 2005, Annals of Neurology

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