Tuesday, September 14, 2004

Brain Scans Show Hypnosis at Work

Another kind of neat science item: from news@Nature.com, here is a blurb about hypnosis. Hypnosis is a valid therapeutic method, although it has been besmirched somewhat by its use as a parlor or stage trick.

Gruzelier studied 24 subjects, half of whom were categorized as succumbing easily to hypnotism, and half of whom were resistant. He scanned the volunteers' brains while they tackled a problem called the Stroop task, a test of mental flexibility that requires subjects to categorize a list of colours presented in a different colour - the word 'green' printed in blue, say - depending either on the name or the actual colour.

Gruzelier tested the subjects before and after they underwent a standard procedure used by hypnotists to put their subjects into a trance. In resistant subjects, the anterior cingulate gyrus was less strongly activated after the procedure than before, showing that their brains were working less hard as they got better at planning how to complete the task.

But in hypnotized volunteers, the anterior cingulate, and the regions that govern it, were more strongly activated when they were in a trance, showing that they were struggling harder to plot their actions, Gruzelier reported. He suspects that this impaired ability to plan for oneself makes people more suggestible.

The article does not say what kind of scan was used, but I assume they used functional MRI scanning.

As a clinical aside, hypnosis can be used in psychotherapy, but in general, it has not been shown to be more effective than any other kind of psychotherapy. For specific uses, though, it may be more effective. Some people, for example, find it to work to help them quit smoking.