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Science: Memory-Triggering Therapy May Help Ward off Cravings for Ex-Addicts
New research with rats and human volunteers suggests a strategy to help ex-drug addicts avoid drug cravings. The approach involves modifying a person’s memories of past drug use, but unlike previous research in this field, the new method doesn’t involve administering memory-blocking drugs.
In a study published in the 13 April issue of Science, Yan-Xue Xue of Peking University in Beijing and colleagues in China and the United States built on the concept of “extinction,” which involves exposing ex-addicts to cues that typically trigger drug cravings, such as the sights, sounds, or smells that a person experienced while using drugs. The patient is sober during the extinction procedure and gradually becomes less sensitive to these cues.
The benefits of extinction often wear off, however, or even disappear spontaneously. The sight of drug paraphernalia or the room where they got high can then lead ex-addicts to begin using drugs once again. Some researchers have tried to boost the effect of the extinction procedure in animal models, using memory-altering drugs that are either not approved for human use or that cause problematic side effects.
Xue and colleagues now describe a purely behavioral intervention that strengthens extinction in rat models of relapse and can also decrease drug craving in humans up to half a year after the intervention.
First, the researchers exposed their test subjects—rats and human volunteers who had undergone detox after heroin addiction—to a very brief reminder of past drug use. The human subjects, for example, watched a short video showing scenes of heroin smoking and injection. This cue retrieved the subjects’ own drug-use memories from long-term storage in the brain. Shortly afterward, the subjects went through the much longer extinction procedure of being exposed to drug-related cues; in the case of the humans, this involved handling drug-related materials and watching videos of heroin use.
Rats that had gone through this intervention were less likely to resume using drugs in response to reminders of their former drug use, compared to rats that had gone through extinction alone. Likewise, memory triggers were less likely to cause drug cravings in the human volunteers—who were in a drug rehabilitation center throughout the study—up to half a year after the intervention.
The benefit of this intervention seems to involve a process called memory reconsolidation, in which an experience (in this case, getting high) is recalled from long-term memory but then altered before it re-enters long-term storage in the brain.
Supporting this idea, the authors found that inducing the initial memory of drug use was only effective if it was done either 10 minutes or one hour before the extinction procedure, which is within the window of time that reconsolidation takes place. This approach was not effective if the initial memory was induced six hours before extinction, presumably because the reconsolidation window had closed by the time the extinction procedure began.
12 April 2012