Do you easily forget things after sleeping? If yes, no worries. While excessive forgetting is a problem, “normal” forgetting is actually necessary. Forgetting during sleep may be controlled by neurons found deep inside the brain. Sleep, learning, and memory are complexly intertwined. However, the influence of these genetic variants on the overnight retention of emotional memories has yet to be discovered.
In this study, researchers investigated the respective influences of the Val66Met (rs6265) polymorphism in the BDNF gene on recognition performance for positive, neutral, and negative images before and after overnight sleep in 36 female students. The polymorphism was selected for the study because it has been shown that BDNF Val66Met interacts with sleep to influence post-sleep learning ability in healthy participants and the BDNF gene is upregulated in the hippocampus during REM sleep, a sleep stage associated with the selective consolidation of emotionally salient memories. All participants began a learning phase at 8.30 PM, followed by an immediate recognition test. Electrodes were then attached for polysomnography (PSG) monitoring. Participants then slept for 8 h between 10.30 PM and 6.30 AM. They were then given 30 min to recover from sleep drowsiness before completing a delayed recognition test. Results showed a significant interaction between the BDNF Val66Met genotype group and image valence on post-sleep recognition performance. This interaction was driven by greater memory for negative and positive images relative to neutral images in Met carriers (AA/AG genotypes). They also found that longer Rapid Eye Movement (REM) sleep duration predicted greater post-sleep recognition performance for negative images in Met carriers but not in Val homozygotes (GG genotype).
In short, these findings suggest that overnight retention of emotional images relative to neutral images was greater in Met carriers than Val homozygotes. REM sleep may have selectively supported the retention of negative images but not positive or neutral images for Met carriers. Conversely, the inverse was true of Val homozygotes.
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