The Effect of One Night of Sleep on Mnemonic Discrimination of Emotional Information.

Mnemonic discrimination is the process of separating similar but distinct experiences and memories in the brain. This process seems to be differently modulated by retention periods that included sleep or only wakefulness. The current study was designed to explore whether a night of sleep may modulate emotional mnemonic discrimination. Thirty-eight participants performed the encoding phase of an emotional mnemonic similarity task composed of 48 negative, 48 neutral, and 48 positive pictures at 9 am (Wake group) or 9 pm (Sleep group). The encoding was followed by an immediate test (T1) in which participants were exposed to 36 targets (old), 36 foils (new), and 36 lures (similar) pictures, and they had to decide whether the pictures were old, new, or similar. Twelve hours later, they performed a delayed test (T2), similar to T1 but with different stimuli. Overall, performances decreased from T1 to T2. There were no differences between groups for recognition memories, whereas the reduction in mnemonic discrimination was more pronounced in the Wake group. Moreover, negative pictures were better discriminated that the neutral and positive ones. In conclusion, the current study showed that a night of sleep can stabilize mnemonic discrimination, regardless of the valence of the encoded stimuli, suggesting that sleep may not preferentially process emotional information.