Monday, July 11, 2005

Musical Hallucinations

From tomorrow's New York Times:
Neuron Network Goes Awry, and Brain Becomes an IPod
The New York Times
Published: July 12, 2005


Only a handful of brain scans have been made of people with musical hallucinations. Dr. Tim Griffiths, a neurologist at the University of Newcastle Upon Tyne in England, performed one of these studies on six elderly patients who developed musical hallucinations after becoming partly deaf.

Dr. Griffiths used a scanning technique known as PET, which involves injecting radioactive markers into the bloodstream. Each time he scanned his subjects' brains, he asked them whether they had experienced musical hallucinations. If they had, he asked them to rate the intensity on a scale from one to seven.

Dr. Griffiths discovered a network of regions in the brain that became more active as the hallucinations became more intense. "What strikes me is that you see a very similar pattern in normal people who are listening to music," he said.

The main difference is that musical hallucinations don't activate the primary auditory cortex, the first stop for sound in the brain. When Dr. Griffith's subjects hallucinated, they used only the parts of the brain that are responsible for turning simple sounds into complex music.

These music-processing regions may be continually looking for signals in the brain that they can interpret, Dr. Griffiths suggested. When no sound is coming from the ears, the brain may still generate occasional, random impulses that the music-processing regions interpret as sound. They then try to match these impulses to memories of music, turning a few notes into a familiar melody.

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