麻豆传媒

THE BRAIN deals with tinnitus in the same way that it deals with 鈥減hantom鈥�
limb pain, where amputees experience pain from a lost limb. So say scientists
who have found that the brain region that perceives sound reorganises itself in
tinnitus sufferers.

Tinnitus is a buzzing or ringing in the ear that only the sufferer can hear.
Loud noise, injury or even wax in the ear can trigger it, but no one really
knows what it is.

Werner M眉hlnickel of the Humboldt University in Berlin and colleagues
played simple tones at four different frequencies to tinnitus sufferers and
healthy volunteers. For each of the tinnitus sufferers, they matched one of the
tones to the frequency of their tinnitus.

The researchers used a technique called magnetoencephalography, which detects
the firing of neurons as changes in the brain鈥檚 magnetic field, to monitor
the responses of the auditory cortex to the tones. In healthy volunteers, the
areas that respond to each frequency are neatly distributed. 鈥淭hey are ordered
like a little chain in the brain,鈥� says M眉hlnickel. But this order is
distorted in tinnitus sufferers (Proceedings of the National Academy of
Sciences, vol 95, p 10340). No one knows whether this is a cause or
consequence of tinnitus.

In phantom limb pain, the brain region that perceives the pain shows similar
distortion.