It is harder to suppress negative, emotional memories after a night's sleep, reveals an article published in Nature Communications this week.
Sleeping after learning new information tends to reorganize how this information is stored and processed, moving it from short-term to long-term memory networks. However, sometimes there are memories that people do not want to recall, and it is unclear how the consolidation that happens during sleep impacts subsequent suppression of those negative memories.
To answer this question, Yunzhe Liu and colleagues analysed a total of 73 male college students performing a series of memory suppression tasks. Students had to learn associations between pairs of images - neutral faces paired with aversive images, so that when they saw the face, they were immediately reminded of the aversive image. Then they were asked to suppress the negative memory when shown the associated faces. This activity was done on two consecutive days, between which all participants reported having had a good night's sleep. The results showed that participants had more trouble suppressing the negative memories after a night's sleep. Brain activity during the task showed that the neural circuits involved in memory suppression, which initially were centred on the hippocampus, shifted to a more distributed pattern in the cortex, and this shift seems to be what makes the aversive memories harder to suppress.
How changes in the brain affect the ability to suppress negative memories could potentially help doctors better understand conditions such as post-traumatic stress disorder.