As this experiment showed, emotional learning circuits unlock and become erasable only when a vivid new experience mismatches what a reactivated emotional learning leads an animal or person to expect. However, once a neural circuit has been unlocked, if nothing is done to erase and overwrite it during the next few hours, the synapses automatically relock—or reconsolidate—and the circuit restabilizes, preserving the original learning. The animal or person is then back at square one—still just as likely to be triggered by a stimulus reminiscent of the original terrifying event.
For the field of psychotherapy, the enormous relevance of later research on the neuroscience of memory reconsolidation is that it’s shown conclusively that using experiential methods to achieve erasure and transformation of the brain’s neural circuits is just as effective as dousing it with chemicals, as was done with Maldonado’s crabs. In fact, in controlled studies with human subjects, experiential methods have successfully erased learned fears, heroin cravings, and other types of emotional learning.
In the study of heroin craving, published in the research journal Science in 2012, the reconsolidation process was carried out with heroin addicts who’d been using the drug for more than 10 years before entering an inpatient detox and rehabilitation program, where the study was conducted. The team of Chinese and American neuroscientists hoped to learn how to use memory reconsolidation to eliminate the almost irresistible learned craving that flares up in addicts when they see drug paraphernalia and other cues that evoke their intense attraction to heroin use and its surroundings.
In the first step of the experiment, the researchers reactivated the targeted learning—that being reminded of getting high leads to the expectation of getting high—of 22 participants. They achieved this reactivation by showing them a five-minute video of scenes of people smoking and injecting heroin. Those images revivified learned expectations of going to places where heroin can be bought, scoring a hit, and shooting up or smoking the drug. This rearoused feelings of heroin craving, and participants rated the strength of their craving using a 0-to-10 scale.
Once the drug use expectations and cravings were retriggered, the participants immediately had a mismatch experience—the second step needed to induce the reconsolidation process. In sharp contrast to the retriggered learning’s expectation of now seeking out and using heroin, the participants experienced being ensconced in the rehab center, where they felt taken care of by helpful, caring staff—and where they knew they would not get to score a fix of heroin. All these features of the actual situation were a strong mismatch of the retriggered expectations of heroin use, so the neural circuits of each addict’s learned expectations unlocked. Fortunately for the clinical use of reconsolidation, the mismatch experience required by the brain to unlock synapses doesn’t have to be as emotionally intense as the target learning. It only has to be a clear, unmistakable departure from what the retriggered learning expects to happen next or expects to be true about the world.
After 10 minutes of that mismatch experience, new learning began, which is the third step of the reconsolidation process. It consisted of one hour of more contact with heroin-related scenes, as well as actually handling heroin-related objects, including simulated heroin. While these activities reactivated participants’ heroin craving, it was now juxtaposed in their minds with the certainty that no seeking or using heroin would follow and that they’d continue to be helped and taken care of, ensuring their comfort and well-being without getting high. This new learning experience could be put into words like this: “After seeing and touching things that remind me of heroin, nothing that involves my using it will happen afterward. I won’t be using, and I’ll be fine. I’m okay without a fix of heroin, even after feeling a craving for it.” Of course, a comforting, safe environment is the norm in detox, but in this case, that norm was used within the steps of the reconsolidation process—meaning that craving and expecting heroin were strongly evoked before reencountering the comfort and safety of the environment.
Researchers then measured the effects of this procedure one day, one month, and six months later and found a persistent, dramatic drop in heroin craving among study participants in response to heroin-related cues. Averaged across participants, heroin cravings decreased by 75 percent, according to their subjective ratings, and the shift was corroborated by measurements of a precipitous drop in blood-pressure increases in response to heroin-related cues. A control group’s craving dropped by only 25 percent.