For millions who struggle with haunting memories, sleep may hold an unexpected key to healing. According to research published in PNAS, scientists have identified a technique that weakens traumatic memories by boosting positive ones during specific sleep phases.
An international research team demonstrated that reactivating positive memories during specific sleep phases could help diminish negative memories, with potential implications for treating mental health conditions.
"We found that this procedure weakened the recall of aversive memories and increased involuntary intrusions of positive memories," the researchers wrote in their published paper.
The study involved 37 participants trained to associate random words with negative images from standardized emotional databases. After a night of sleep to consolidate these memories, researchers attempted to override half of the negative associations by linking the same words with positive images, such as calm landscapes and smiling children, in contrast to the negative pictures of injuries or dangerous animals.
During the second night, researchers played recordings of the nonsense words while participants were in non-rapid eye movement sleep, a phase crucial for memory consolidation. The team monitored brain activity using electroencephalography equipment.
The researchers observed increased theta-band brain activity linked to emotional memory processing in response to audio memory cues. This activity was notably higher when positive cues were used.
Through questionnaires conducted the next day and several days later, participants showed a decreased ability to recall negative memories that had been paired with positive ones. They were more likely to experience spontaneous positive memory intrusions for these word associations and viewed them with a more positive emotional bias.
"A noninvasive sleep intervention can thus modify aversive recollection and affective responses," the researchers wrote. "Overall, our findings may offer new insights relevant to treating pathological or trauma-related remembering."
The researchers noted limitations of their laboratory study, acknowledging that viewing negative images in a controlled setting does not have the same impact as experiencing real-world trauma, which might be more difficult to override.
Previous research has shown that the brain briefly replays memories during sleep. Scientists have been exploring how this process could be controlled to reinforce or diminish negative memories.
"Our findings open broad avenues for seeking to weaken aversive or traumatic memories," the researchers concluded in their paper.
The study represents an early step in understanding memory modification during sleep. Researchers note that additional research is needed to determine the long-term effectiveness and potential therapeutic applications of this technique.
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