The precise coupling between slow oscillations (SO) and spindles is critical for sleep-dependent consolidation of declarative memories. Here, we examined whether this mechanism also operates in the stabilization of human motor memories during NREM sleep. We hypothesized that if the coupling of these oscillations is instrumental to motor memory consolidation then only SO-coupled spindles would predict long-term memory. We found that sleep enhanced long-term memory retention by 34%. Motor learning increased the density of spindles but not their frequency, duration or amplitude during NREM sleep. This modulation was manifested locally over the hemisphere contralateral to the trained hand. Although motor learning did not affect the density of SOs, it substantially modulated the spindle-SO coupling in an inter-hemispheric manner, suggesting it may rather increase the ability of slow oscillations to promote thalamic spindles. The fact that only coupled spindles predicted long-term memory points to the association of these oscillations as a fundamental signature of motor memory consolidation. Our work provides evidence in favor of a common mechanism at the basis of the stabilization of declarative and non-declarative memories.
bioRxiv Subject Collection: Neuroscience