October 1, 2012, 5:09 p.m.


Hypnosis has come a long way since the swinging pocket watch -- proving useful for pain control, management of phobia and anxiety, in the treatment of post-traumatic stress disorder, and as a supplement to analgesia during medical procedures.
But hypnosis is not for everybody. Or, more to the point, everybody is not equally amenable to the the technique's mental magic, which can help a person experience imagined sensations or movements or not feel sensations -- such as intractable pain -- that are all too real. A new study uses brain scanners to distinguish between people who've got a knack for the technique and those whose grip on reality is just too tight for them to benefit much from hypnosis.
The research, published Monday in the Archives of GeneralPsychiatry, proceeds from a widely observed phenomenon: that some people are readily and fully hypnotizable while others are not. Researchers from Stanford University put 12 subjects already identified as highly hynotizable into brain scanners that measured the structure of their brains and watched them at rest and at work. Twelve other subjects who were not readily hypnotized were put through the same battery of scans for comparison.
The researchers found no differences between the typical structures of the two groups' brains: They were similarly sized, had about the same ratio of gray matter to white matter, their component parts looked pretty much the same. But when the researchers looked at the subjects' brains at rest, they noticed that the brains of the "high-hypnotizeable" group behaved a bit differently than those of the "low-hypnotizeable" group.
Specifically, the researchers found differences in the two groups' "Default Mode Network," the complex of brain regions that hums along when a person is not engaged in a specific cognitive task such as reading or navigating an unfamiliar road.
When the Default Mode Network is engaged, a person's mind is wandering, although for most, it seldom wanders far from oneself. Autobiographical memories, feelings, one's relationships with others, how others behave toward or perceive oneself: These are largely the grist for the Default Mode Network's mill, and the brain regions that come to life in these moments are largely associated with these functions.
For that reason, the Default Mode Network is widely thought of as the seat of "the self" in the human brain.
But for the highly hypnotizable, a brain structure associated with purposeful attentional control -- the dorsolateral prefrontal cortex -- is activated alongside the Default Mode Network when the mind is at rest. This would suggest that the highly hynotizable have a tighter coordination between brain areas where attention, emotion, action and intention are processed, wrote the authors of the study. And it means that for the highly hynotizable, there's something about the self -- or the self's sensations -- that can be modified by purposeful attention.
To Stanford University psychiatrist David Spiegel, one of the study's co-authors, the differences seen between the two groups on brain scan appear to confirm the impressions of practitioners like him: The highly hynotizable are people who can readily immerse themselves in thinking about things without having their attention interrupted by pesky reminders of reality or of competing cognitive demands. They can harness their minds to imagine something about themselves -- and make it so.
In everyday life, says Dr. Spiegel, these high-hypnotizable people are notably different than their less hynotizable peers: "They get sidetracked by sunsets and lost in movies; they tend to show up three hours late for things because they lost track of time," Spiegel says. By contrast, he adds, those who are resistant to hypnosis don't suspend judgment easily, tend to be more fastidious in their habits and less trusting of people.
Will physicians and mental health professionals who use hypnosis to help their patients start giving them brain scans to see if it'll work? No, says Spiegel. But they'll probably trust their instincts in assessing patients who could benefit from hypnosis, he said. And they'll understand just a little bit better why it works -- for some -- as well as it does.