The difference between American Idols and the karaoke-challenged may be more than voice deep. Researchers have found that tone-deaf people have an unusual distribution of neurons in the front of their brains.

Tone-deaf individuals cannot recognize familiar songs without lyrics and do not realize when their own singing is out of tune. About 4 percent of people carry this trait. Previously researchers have hunted for the roots of this musical inability in the auditory centers of the brain. But they did not find any differences in these regions between tone-deaf and normal listeners. So Krista Hyde of the Montreal Neurological Institute at McGill University and her colleagues scanned entire brains to search for anatomical anomalies. They found that the amusical subjects had less white matter--neuron axons that are wrapped in an insulating sheath of myelin--in the right inferior frontal gyrus. The worse they performed on musical pitch tests, the less white matter they had.

This article was originally published with the title How the Brain Tunes Out.

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