Good suggestion. . Brain activity associated with visual processing is dampened by a post-hypnotic suggestion.

Unblocking the Mind

Something as simple as a mosquito bite can create a dilemma for the brain: We want to scratch the itch, yet our mothers told us not to. New research demonstrates that hypnosis can be used to overcome such cognitive conflicts by altering activity in specific regions of the brain.

Hypnotic suggestion has previously been used to overcome cognitive conflict, but no one had investigated how it affects the brain. A classic method of studying cognitive conflict is to ask people to name the color of the ink with which words are written. When shown the word "green" written in blue ink, for example, subjects tend to hesitate and make mistakes. If the same subjects are hypnotized to see such words as meaningless symbols, however, they have a much easier time identifying the ink.

In the new study, Amir Raz, a cognitive neuroscientist at Columbia University in New York, and colleagues focused on the brain activity underlying this effect. As in their earlier behavioral studies, highly-hypnotizable subjects who had been given the post-hypnotic suggestion performed better than less-suggestible subjects when presented with a conflict between word meaning and color. Brain imaging showed dampened activity in the best performers but not in the less-suggestible individuals. The affected areas are those responsible for the early stages of visual processing and the anterior cingulate cortex (ACC), a region known to be involved in attention, emotional control, and self-regulation, the researchers report online this week in Proceedings of the National Academy of Sciences.

"The reason this is amazing is that reading is considered an automatic process," says Raz. The fact that a specific suggestion overrides this process by altering brain activity, he argues, indicates that hypnosis can be used to turn specific brain areas off and on.

"A lot of people think hypnosis is suspect," says Colin MacLeod, a cognitive psychologist at the University of Waterloo in Canada. But "this [study] gives hypnosis a lot more currency than it might have had in the cognitive world."

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