Scientists demonstrate a novel sleep-based technique to weaken negative memories

In a recent study published in the Proceedings of the National Academy of Sciences, researchers detailed a way to weaken the recall of negative memories by reactivating newer, positive memories during sleep. The technique, known as targeted memory reactivation, not only diminished the intensity of negative memories but also heightened the involuntary recall of positive memories. This process further increased participants’ positive emotional judgments after sleep. The findings suggest that memory manipulation during sleep could pave the way for innovative treatments for trauma and emotional distress.

Negative memories, particularly those that emerge involuntarily, can significantly impair mental health, disrupting daily life and cognitive functioning. Traditional methods of managing these memories, such as therapy or medication, often require effortful emotional engagement and may not always succeed in alleviating the emotional burden. Sleep plays a critical role in processing memories and offers a unique avenue for modifying how memories are stored and retrieved. Inspired by previous research showing that activating positive memories can improve emotional well-being, the researchers aimed to explore whether positive memories could be used to “interfere” with older, negative ones during sleep.

The study involved 37 participants, primarily college-aged adults, who underwent a multi-day experimental procedure. Participants began by forming associations between random spoken words and emotionally negative images, such as distressing or aversive scenes. These associations were established during a learning session on the first evening, followed by an overnight sleep to consolidate the memories.

On the second evening, participants learned new associations between a subset of the previously used words and emotionally positive images, creating “interfering” positive memories. Half of the original word-image pairs remained unchanged to serve as a control group. After this session, participants underwent another night of sleep, during which the researchers used targeted memory reactivation. This technique involved playing the audio cues (spoken words) linked to both the positive and negative memories while the participants were in a specific phase of sleep known as non-rapid eye movement sleep.

The researchers monitored participants’ brain activity using electroencephalography, which tracks electrical signals in the brain. This allowed them to ensure the participants remained in the correct sleep phase for memory reactivation. The auditory cues were presented at low volumes to subtly trigger memory recall without waking the participants.

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The next morning, participants completed tasks to assess how well they recalled the negative and positive memories. They also provided emotional ratings for the words and images to determine how their emotional responses had shifted. Similar tests were repeated five days later to evaluate the durability of the effects.

The researchers found that the targeted reactivation of positive memories during sleep weakened participants’ ability to recall the associated negative memories. This effect was specific to the memories in the “interference” group—those for which both negative and positive associations had been created. Memories in the control group, which had no competing positive associations, were unaffected by the reactivation process.

Second, the reactivation technique increased the frequency of involuntary positive memory intrusions during the recall of negative memories. For example, participants were more likely to spontaneously think of positive images when prompted with words that had been linked to both positive and negative memories.

Additionally, participants exhibited a more positive emotional bias toward the reactivated cues. Their responses in tasks requiring quick judgments about the emotional valence of the words became more positive, suggesting that the reactivation process influenced not only memory recall but also emotional perception.

Brain activity during sleep provided further insights. The researchers observed increased theta-band activity—a type of brainwave associated with emotional memory processing—during the presentation of memory cues. This activity was particularly pronounced for positive memories, indicating that the reactivation process preferentially targeted the newer, positive associations.

While the results are promising, the study has several limitations. One key limitation is that the emotional memories used in the experiment were artificially created in a laboratory setting and may not fully capture the complexity of real-life traumatic experiences. The findings, therefore, need to be replicated in studies involving more naturalistic or autobiographical memories.

Additionally, the researchers focused on a specific phase of sleep and used carefully controlled cues. Future research could explore how other sleep phases, such as rapid eye movement sleep, might influence memory reactivation and emotional processing. The long-term effects of this technique also remain unclear—whether the weakening of negative memories persists over months or years is yet to be determined.

Finally, translating these findings into clinical applications will require careful consideration. For individuals with severe trauma, introducing positive memories for interference may not always be feasible, and the ethical implications of deliberately altering memories must be addressed.

“By demonstrating the memory and affect benefits of reactivating positive interfering memories, our study invites future research to harness the potential of sleep-based memory editing techniques in managing aversive memories and promoting psychological well-being,” the researchers concluded.

The study, “Aversive memories can be weakened during human sleep via the reactivation of positive interfering memories,” was authored by Tao Xia, Danni Chen, Shengzi Zeng, Ziqing Yao, Jing Liu, Shaozheng Qin, Ken A. Paller, S. Gabriela Torres Platas, James W. Antony, and Xiaoqing Hu.