One-Note Wonders

Why can some singers croon in tune while others warble off-key? The answer's in the brain, not the ear. Researchers have identified a neural network which seems to grant certain people perfect pitch.

Most musicians have relative pitch, or the ability to identify the interval between two tones. But perfect or absolute pitch--the ability to name or produce a note on demand--is rare.

Robert Zatorre, Ph.D., associate professor at the Montreal Neurological Institute at McGill University, used positron emission tomography (PET) to monitor the brain activity of 20 musically trained subjects as they listened to various tones.

When asked to name the interval formed by two notes, subjects with relative pitch used the right inferior frontal part of the cortex, which maintains working memory. These musicians, contends Zatorre, must consciously remember each sound in order to classify the notes' relationship. In contrast, perfectly-tuned individuals showed no activity in this are. suggesting that they access information already stored in the brain.

"If you don't have perfect pitch," Zatorre explains, "you have to hold one note in your memory till the second comes along. Then you re-sing the interval in your head. But with perfect pitch, you automatically know that they're, say, an F and an A, and form a major third."

PET scans of people listening to single notes show that only those with perfect pitch fire the left dorsolateral frontal cortex, a brain region used in associative learning. Zatorre believes that when these musicians hear a note, its verbal name is also retrieved. "Their association circuitry seems to be more highly developed," he says. "They hear a sound, it's linked to a label and the cortex lights up."

PHOTO (COLOR): Most musicians have relative pitch, or the ability to identify the interval between two tones.