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Sleep and memory studies often focus on overnight rather than longterm memory changes, traditionally associating overnight memory change (OMC) with sleep architecture and sleep patterns such as spindles. In addition, (para)sympathetic innervation has been associated with OMC after a daytime nap using heart rate variability (HRV). In this study we investigated overnight and longterm performance changes for procedural memory and evaluated associations with sleep architecture, spindle activity (SpA) and HRV measures (RR interval [RRI], standard deviation of RR intervals [SDNN], as well as spectral power for low [LF] and high frequencies [HF]). All participants (N = 20, Mage = 23.40 2.78 years) were trained on a mirrortracing task and completed a control (normal vision) and learning (mirrored vision) condition. Performance was evaluated after training (R1), after a fullnight sleep (R2) and 7 days thereafter (R3). Overnight changes (R2R1) indicated significantly higher accuracy after sleep, whereas a significant longterm (R3R2) improvement was only observed for tracing speed. Sleep architecture measures were not associated with OMC after correcting for multiple comparisons. However, individual SpA change from the control to the learning night indicated that only “SpA enhancers” exhibited overnight improvements for accuracy and longterm improvements for speed. HRV analyses revealed that lower SDNN and LF power was associated with better OMC for the procedural speed measure. Altogether, this study indicates that overnight improvement for procedural memory is specific for spindle enhancers, and is associated with HRV during sleep following procedural learning. P15370 W1233G17 (VLID)4373764

Many studies investigating sleep and memory consolidation have evaluated fullnight sleep rather than alternative sleep periods such as daytime naps. This multicentre study followed up on, and was compared with, an earlier fullnight study (Schabus et al., 2004) investigating the relevance of daytime naps for the consolidation of declarative and procedural memory. Seventysix participants were randomly assigned to a nap or wake group, and performed a declarative wordpair association or procedural mirrortracing task. Performance changes from before to after a 90min retention interval filled with sleep or quiet wakefulness were evaluated between groups. Associations between performance changes, sleep architecture, spindles, and slow oscillations were investigated. For the declarative task we observed a trend towards stronger forgetting across a wake period compared with a nap period, and a trend towards memory increase over the fullnight. For the procedural task, accuracy was significantly decreased following daytime wakefulness, showed a trend to increase with a daytime nap, and significantly increased across fullnight sleep. For the nap protocol, neither sleep stages, spindles, nor slow oscillations predicted performance changes. A direct comparison of day and nighttime sleep revealed that daytime naps are characterized by significantly lower spindle density, but higher spindle activity and amplitude compared with fullnight sleep. In summary, data indicate that daytime naps protect procedural memories from deterioration, whereas fullnight sleep improves performance. Given behavioural and physiological differences between day and nighttime sleep, future studies should try to characterize potential differential effects of fullnight and daytime sleep with regard to sleepdependent memory consolidation. P-15370-B02 W1233-G17 (VLID)2502269