EEG sigma and slow wave activity during NREM sleep correlate with overnight declarative and procedural memory consolidation

Objectives: Previous studies suggest that sleep-specific brain activity patterns such as sleep spindles and EEG slow wave activity (SWA) contribute to the consolidation of novel memories. The generation of both sleep spindles and SWA relies on synchronized oscillations in a thalamo-cortical network that might be implicated in synaptic strengthening (spindles) and downscaling (SWA) during sleep. Methods: This study further examined the association between EEG power during NREM sleep in the spindle (sigma, 12–16 Hz) and slow wave frequency range (0.1–3.5 Hz) and overnight memory consolidation in 20 healthy subjects (10 men, 27.1 ± 4.6 year). Results: We found that both EEG sigma power and SWA were positively correlated with the pre-post sleep consolidation of declarative (word list) and procedural (mirror tracing) memories. Conclusions: These results, although only correlative in nature, are consistent with the view that processes of synaptic strengthening (sleep spindles) and synaptic downscaling (SWA) might act in concert to promote synaptic plasticity and the consolidation of both declarative and procedural memories during sleep.