Triggering bad memories to reactivate in REM sleep – the period when people dream most vividly – reduces the emotion associated with these memories on waking, a new study has suggested.
It is the first research to suggest this technique could have the potential for use as a tool for the treatment of anxiety disorders, potentially including post-traumatic stress disorder (PTSD).
The study was carried out by psychologists from Cardiff University, along with experts from the University of Manchester, and the findings are published in Communications Biology.
Sleep plays a crucial role in the consolidation of memories – and this discovery adds to a growing body of evidence that sleep can help to “decouple” emotions from difficult experiences.
In particular, the “sleep to forget, sleep to remember” hypothesis suggests reactivation during REM sleep can lead to a dampening of the emotion around bad memories since the reactivation happens when the body is in deep sleep and will not respond.
The scientists tested this hypothesis in rapid-eye-movement (REM) and in slow-wave sleep (SWS), often referred to as deep sleep, by using targeted memory reactivation (TMR). TMR involves pairing sounds with learned material during the daytime, then re-presenting the sounds at night to trigger the memory.
In this study, 46 participants rated picture-sound pairs in terms of how upsetting they were before and after sleep. They divided the participants into two groups, an REM group and a SWS group. In each group, half of the negative and half of the neutral image/sound pairs were reactivated in sleep (REM or SWS) via TMR.
They found that reactivation in REM but not SWS led to a significant reduction in how upsetting participants found the pictures the next day. This was true for both negative and neutral pairs, but the effect was driven by the negative ones.
Sleep psychologist Professor Penny Lewis, from Cardiff University Brain Research Imaging Centre (CUBRIC), said: “These results are important because they provide strong support for the idea that triggering emotional memories to reactivate during REM sleep can be used to dampen negative emotions that exist around a bad memory.”
The team intends to look at brain activity associated with this emotional dampening in their next study. They hope to find that this method of dampening emotional reactions also reduces engagement of an area called the amygdala, which is strongly involved in individual emotional responses.
Source: Cardiff University