Memory generalization and overgeneralization in sleep

Overgeneralization and sleep quality disruption are major components of anxiety and post-traumatic stress disorder (PTSD). This study attempts to elucidate potential links between these elements. We designed a paradigm wherein participants learned associations between three faces and positive, negative, or neutral outcomes. Subsequently, we evaluated their generalization of these faces by examining responses to morphed faces resembling the initially associated faces before and after consolidation during daytime wakefulness or full-night sleep. Our findings reveal that post-sleep, participants tended to generalize positively associated faces over negatively associated ones, a trend not observed during wakefulness. By recording fMRI during the learning phase, we identified a network of brain regions, including the amygdala, nucleus accumbens, caudate, anterior cingulate, and anterior superior temporal gyrus, displaying similar patterns: Increased activity within this network during learning correlated with the positive stimulus generalization during sleep and the restoration of the negative stimuli generalization occurred during learning. Notably, this activity did not correlate with generalization during wakefulness consolidation. In a supplementary experiment, we recorded high-density EEG during sleep and observed a correlation between the power of sleep spindles and the generalization of positive stimuli. These findings underscore the significance of sleep in both generalization processes and its role in restoring negative stimuli generalization and promoting positive stimuli generalization, thus advancing our understanding and potentially informing therapeutic strategies for anxiety and PTSD.