In Eternal Sunshine of the Spotless Mind, Jim Carrey and Kate Winslet decided to erase their shared memories to avoid the emotional burden of their separation. They used a new technology developed by Dr. Mierzwaik, able to erase the "core" of any memory, leading to the disruption of the associated emotions. During the day, the brain activity elicited by target objects (e.g., a picture) associated with specific events (e.g., a beach day) are mapped using a futuristic electroencephalography. The next night, the targeted memories are reactivated and then destroyed, leaving the person unaware of both their content and related emotions.
We can't erase memories yet. But our lab is working on a new tool that could lessen the emotional impact of burdening memories by targeting them during sleep. Indeed, as in Eternal Sunshine, what is important is not erasing the content of a memory itself, but rather taking control over their related emotions. That is, we don't need to forget the name of our previous partner, but we may want to remember that name without feeling a pang in our hearts. Besides helping the aching hearts, being able to control our responses to burdensome emotional stimuli is of the essence when our health is at stake. Blood phobics, for instance, don't seek medical treatment mostly because of their dysfunctional way of regulating emotions even to the idea of medical procedures. By capitalizing on the power of sleep, our lab aims to modify such difficult emotional memories with no conscious effort by the individual.
Scientists tend to agree that during our sleep information that we have learnt during the day is reactivated to be strengthened and stabilized. But if during the day we match a sensory cue (a sound or a smell) with target information (a picture or a word, for instance) and then we re-present the same cue alone during sleep, we can improve the consolidation of such memories. In other words, researchers have shown that it is possible to bias the sleeping brain to preferentially process specific memories when cued.
Similarly, we can target emotional memories, too. A way scientists do that in the lab is by using fear conditioning paradigm. A neutral stimulus (for example a face presented on a screen) is associated with a threatening stimulus, such as an irritating electrical shock. After several face-shock paired presentations, the mere presence of the face will induce a fear response, evident from the increased sweating and heart acceleration of the participant. Adding to the face-shock pairs either a sound or a smell cue, and then and then presenting the cue during participants' deepest sleep stage significantly reduces the threatening power of the face previously paired with the shock. In other words, researchers were able to modify the emotions associated with a specific memory, without any conscious effort by the participants.
Being aware that a technique involving forms of (un)learning in states of unconsciousness requires deep ethical considerations, we can apply these findings to the development of clinical protocols for disorders such as specific phobias, trauma-related, and eating disorders, for which many classic treatments entail highly distressing side effects.
As Dr. Mierzwaik says, "By the time you wake up in the morning, all the memories we have targeted will have withered and disappeared." Maybe we will not be able to make the memories disappear by the time we wake up, but we may have found a way to make them less traumatic.