Miércoles 1 de Noviembre de 2006, Ip nº 177

Looking at Your Brain on Drugs
Por Emily Singer

For a recovering drug addict, the sight of a hypodermic needle or a crack pipe--or even the exterior of a drug house--can trigger powerful cravings. Now scientists hope to use new brain-imaging technology to train substance abusers to control cravings. The addicts would literally watch real-time images of brain blood flow and use mental exercises to try to control their brain activity.

"We hope to develop a novel therapeutic for addiction, which will create a new way of treating these patients," says Christopher deCharms, founder of Omneuron, a brain-imaging company in Menlo Park, CA, that is planning a study to test the approach.

While much is still unknown about what happens in the brain during a craving for drugs such as cocaine and nicotine, recent imaging studies have shown that certain parts of the brain are hyperactive in addicts when they are shown drug-related pictures or movies. DeCharms and colleagues plan to build on these findings using a new type of brain-imaging technology that enables both subject and researcher to look at the brain's activity as the subject thinks. Known as real-time functional magnetic resonance imaging, or fMRI, the technology measures blood flow to different parts of the brain, indicating which parts of the brain are most active at a given time.

Omneuron researchers theorize that an addict could use mental exercises to try to increase or decrease activity in a specific part of the brain, enlisting the fMRI feedback to guide his or her progress. For example, in a cognitive-therapy exercise taught in pain clinics, patients with chronic pain are instructed to imagine their brain releasing pain-killing chemicals. The fMRI feedback process is similar to biofeedback, through which people learn to control their blood pressure or heart rate by getting constant feedback on their vital signs. With the Omneuron approach, the feedback would come from a monitor showing the addicts real-time pictures of blood flow in the brain.

DeCharms's group has shown that the method works for controlling chronic pain: patients who were taught to control activity in the anterior cingulate cortex, an area involved in processing pain, experienced more pain relief than control groups did. (See Seeing Your Pain.) In the new study, researchers plan to compare brain-activity patterns in addicts when they are using versus not using a drug, or when they are shown pictures that trigger drug cravings versus neutral images. Researchers would then try to teach the subjects how to voluntarily bring their brain activity back to its calm, drug-free state.

"We're just in the early stages of this research, but the hope is that rather than using purely pharmacologic or cognitive [therapy] approaches, this would provide another avenue to treat this major disorder," says deCharms. His group has done an initial pilot study of the technology and is now in the planning stages of a larger study. It's too early to estimate when such a technique, if successful, would be available to patients.

Brain-imaging and addiction experts are excited about the possibilities. Nora Volkow, director of the National Institute on Drug Abuse (NIDA), says she has been considering this application of real-time fMRI since deCharms first published his paper showing that the technique could help chronic pain. (The research for this paper was funded by NIDA.) "Wouldn't it be wonderful if we could train the brain to regulate the response to craving?" she says.

Hans Breiter, a psychiatrist and researcher at Massachusetts General Hospital, in Boston, says scientists have been hoping to develop this type of application since fMRI was first developed in the early 1990s. "It's taken a long time for the needed technological improvements to fall into place," he says. "I'm pleased someone is going to do hard work to try to make it work." He cautions that imaging areas known to be hyperactive in drug addicts, such as the anterior cingulate and the insula, is very challenging and requires a lot of technical expertise.

"One caveat is whether the exercises done with real-time fMRI can then be extended to real-life situations," adds Rita Goldstein, a research scientist at Brookhaven National Laboratory, in Upton, NY. "But the prediction is that it will be like exercise, strengthening the functions subserved by those specific brain regions."

If the feedback technique is effective, it could ultimately be combined with other treatment strategies, such as desensitization or medication. Some behavioral treatments, for example, teach drug abusers to try to dissociate drugs cues, such as a needle or a cigarette, from the emotional feelings these visual stimuli elicit. Cycloserine, an antibiotic that also affects the brain's learning and memory systems, has been shown to boost the effectiveness of this approach for people with a fear of heights. Volkow suggests that the same could possibly be done with real-time fMRI and addiction.

  30/10/2006. MIT's Technology Review.