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Tone deafness may be caused by brain abnormality

August 16, 2004|Jamie Talan | Newsday

Can't keep a tune? Blame your brain.

People who can't discriminate between musical tones suffer from amusia, or tone deafness, and Canadian researchers say they have identified a region in the brain they believe is responsible. Krista Hyde and her colleagues at the University of Montreal have been scanning the brains of 20 people who've been tone deaf since birth and have narrowed the hunt to the right auditory cortex, an area of the brain that processes pitch perception.

Amusia is no laughing matter, Hyde, a doctoral student, says. Music is such a major element of our culture, she said, that the condition "robs them of their experience of music.... A beautiful symphony can sound like noise."

The researchers suspect that as much as 4% of the world's population has a congenital brain abnormality that renders it tone deaf. Others can acquire amusia after head trauma or stroke.

Of 100 people who responded to ads seeking people who can't carry a tune, Hyde said only 20 qualified for a true diagnosis of amusia -- indicating many who think they're tone deaf instead simply aren't good vocalists.

Hyde's postdoctoral research was designed to figure out why people had severe problems processing music despite normal intelligence, memory and language skills. Her findings, published in the May issue of Psychological Science, suggest that a brain abnormality impairs pitch processing.

Robert Zattore, a professor of neuroscience at the Montreal Neurological Institute, part of McGill University in Montreal, said that the human brain has evolved so that left and right sides of the auditory cortex have different structures and functions -- unlike most brain regions, which are symmetrical.

Studies by Zattore and others suggest that the left auditory cortex contains more white matter than the right, suggesting that the left evolved to handle rapid-firing human speech. The right is slower in processing information but more accurate, which may explain its involvement in pitch perception.

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