04 May 2004

Biofeedback and pain supression

This suggests we can add biofeedback to hypnotic analgesia and meditation as surprisingly effective analgesic techniques.

People can learn to suppress pain when they are shown the activity of a pain-control region of their brain, a small new study suggests. The new biofeedback technique might also turn out to be useful for treating other conditions.

Twenty years ago Rosenfeld found that he could change the pain threshold in mice by training them to alter their brainwave patterns through a process called conditioned learning, where an altered brainwave state was rewarded by direct stimulation of the reward centres in their brains. Since this meant placing an electrode into the brain, however, his team never tried the technique on people.

Now Fumiko Maeda, Christopher deCharms and their colleagues at Stanford University in California have tried showing people real-time feedback from a functional magnetic resonance imaging (fMRI) scanner.

The eight volunteers saw the activity of a pain-control region called the rostral anterior cingulate cortex represented on a screen either as a flame that varied in size, or as a simple scrolling bar graph. This brain region is known to modulate both the intensity and the emotional impact of pain.

During the scans the volunteers had to endure painful heat on the palm of their hand. They were asked to try to increase or decrease the signal from the brain scanner and to periodically rate their pain sensations.

It took just three 13-minute sessions in the scanner for the eight volunteers to learn to vary the brain activity level, and thus to develop some control over their pain sensations, the researchers reported at the Cognitive Neuroscience Society meeting in San Francisco last week.

The effect seemed to last beyond the sessions in the scanner, although the researchers have yet to determine how strongly and for how long.

The volunteers could not explain how they did it. The researchers ruled out other explanations for the effect through a series of controls. They gave people false feedback data, no feedback at all, or feedback from a part of the brain unrelated to pain control. They also sometimes asked people to pay attention to the pain or distracted their attention away from it.