Targeted memory reactivation during sleep promotes strengthening of partially overlapped memories

Oyarzún, J. P. 1, 2 , Morís, J. 4, 5 , Luque, D. 5 , de Diego-Balaguer, R. 1, 2, 3 & Fuentemilla, L. 1, 2

1 Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute, L Hospitalet de Llobregat, 08097 Barcelona, Spain
2 Department of Basic Psychology, Campus Bellvitge, University of Barcelona, L Hospitalet de Llobregat, 08097 Barcelona, Spain
3 Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
4 Department of Basic Psychology, University of Málaga, Málaga, Spain
5 Institute of Biomedical Research of Málaga (IBIMA), Málaga, Spain

Studies employing target memory reactivation have demonstrated a highly specific strengthening for reactivated memories during sleep. However, it is unknown whether such memory reactivation has an effect on other partially overlapped memories, and if this is so, whether they become strengthened or interfered. During the 1st learning task, 15 participants learned locations of 15 pairs of identical cards. This followed a 2nd learning task in which auditory cues signaled the appearance of the same 15 cards with its pair in a different location. EEG recordings during a sleep nap followed for 70 minutes, time at which a selected set of learned memories was reactivated via the presentation of the auditory cues. When participants awoke, they were requested to recollect the location of the pairs learned during the 1st task. We found higher memory accuracy for those memories that were selectively reactivated during sleep, suggesting that the reactivation of memory from the 2nd learning during sleep may have promoted the strengthening of memories with overlapping information from the 1st learning. Furthermore, EEG activity elicited during sleep was related to performance. Our data supports the idea that selective memory reactivation promotes the integration with, rather than the interference of, other overlapping memories.