Summary: Previous research found sound cues played during sleep can improve a person’s memory. A new study reports that sound cues during sleep can also help to weaken intrusive and traumatic memories. Researchers say sound cues during sleep could be used to both increase or decrease the ability to recall specific memories.
Source: University of York
Playing sounds to people while they sleep can be used to help them to forget specific memories, a new study has revealed.
The early-stage discovery, by researchers at the University of York, could potentially be developed into techniques to help weaken traumatic and intrusive memories, the authors of the study say.
Previous research found that playing ‘sound cues’ during sleep can be used to boost specific memories, but this latest study provides the first strong evidence that the technique can also be used to help people to forget.
First author of the study, Dr Bardur Joensen, a former PhD student at the Department of Psychology, University of York, said: “Although still highly experimental at this stage, the results of our study raise the possibility that we can both increase and decrease the ability to recall specific memories by playing sound cues when an individual is asleep.
“People who have experienced trauma can suffer a wide range of distressing symptoms due to their memories of those events. Though still a long way off, our discovery could potentially pave the way to new techniques for weakening those memories that could be used alongside existing therapies.”
For the study, 29 participants learnt associations between overlapping pairs of words. For example, they were asked to learn the word pairs ‘hammer – office’ and ‘hammer – Cardi B’.
The participants then slept overnight in the University of York’s sleep lab. The research team analysed their brainwaves and when they reached deep or slow-wave sleep (also known as stage-three sleep) they were quietly played the word denoting the object (i.e. hammer).
Previous research found that playing ‘sound cues’ during sleep can be used to boost specific memories, but this latest study provides the first strong evidence that the technique can also be used to help people to forget. Image is in the public domain
Previous research had found that learning a pair of words, and playing a sound associated with that pair during sleep, improved participants’ memory for the word pair when they woke in the morning.
This time, when the pairs of words were overlapping, they found an increase in memory for one pair, but a decrease in memory for the other pair. This suggests it is possible to cause selective forgetting by playing associated sounds during sleep.
According to the researchers, sleep played a crucial role in the effects they observed in their study.
Senior author of the study, Dr Aidan Horner from the Department of Psychology at the University of York, said: “The relationship between sleep and memory is fascinating. We know that sleep is critical for memory processing, and our memories are typically better following a period of sleep. The exact mechanisms at play remain unclear, but during sleep it seems that important connections are strengthened and unimportant ones are discarded.
“This research raises the possibility that this process could be manipulated so that sleep could be used to help weaken painful memories.
“The next steps for our research team are to establish how these cues cause forgetting, so that we can turn the effect on and off, and whether we can use the same technique to weaken existing real-world memories.”
Targeted memory reactivation during sleep can induce forgetting of overlapping memories
Memory reactivation during sleep can shape new memories into a long-term form. Reactivation of memories can be induced via the delivery of auditory cues during sleep. Although this targeted memory reactivation (TMR) approach can strengthen newly acquired memories, research has tended to focus on single associative memories.
It is less clear how TMR affects retention for overlapping associative memories. This is critical, given that repeated retrieval of overlapping associations during wake can lead to forgetting; a phenomenon known as retrieval-induced forgetting (RIF).
We asked if a similar pattern of forgetting occurs when TMR is used to cue reactivation of overlapping pair-wise associations during sleep. Participants learnt overlapping pairs; learnt separately, interleaved with other unrelated pairs.
During sleep, we cued a subset of overlapping pairs using TMR. While TMR increased retention for the first encoded pairs, memory decreased for the second encoded pairs. This pattern of retention was only present for pairs not tested prior to sleep.
The results suggest that TMR can lead to forgetting; an effect similar to RIF during wake. However, this effect did not extend to memories that had been strengthened via retrieval prior to sleep. We therefore provide evidence for a reactivation-induced forgetting effect during sleep.