Napping to renew learning capacity: enhanced encoding after stimulation of sleep slow oscillations

Authors

  • Daria Antonenko,

    1. Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany
    2. Department of Neurology, Charité University Medicine, Berlin, Germany
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  • Susanne Diekelmann,

    1. Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany
    2. Department of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany
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  • Cathrin Olsen,

    1. Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany
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  • Jan Born,

    1. Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany
    2. Department of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany
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  • Matthias Mölle

    Corresponding author
    1. Department of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen, Germany
    • Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany
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Correspondence: Matthias Mölle, 1Department of Neuroendocrinology, as above.

E-mail: moelle@kfg.uni-luebeck.de

Abstract

As well as consolidating memory, sleep has been proposed to serve a second important function for memory, i.e. to free capacities for the learning of new information during succeeding wakefulness. The slow wave activity (SWA) that is a hallmark of slow wave sleep could be involved in both functions. Here, we aimed to demonstrate a causative role for SWA in enhancing the capacity for encoding of information during subsequent wakefulness, using transcranial slow oscillation stimulation (tSOS) oscillating at 0.75 Hz to induce SWA in healthy humans during an afternoon nap. Encoding following the nap was tested for hippocampus-dependent declarative materials (pictures, word pairs, and word lists) and procedural skills (finger sequence tapping). As compared with a sham stimulation control condition, tSOS during the nap enhanced SWA and significantly improved subsequent encoding on all three declarative tasks (picture recognition, cued recall of word pairs, and free recall of word lists), whereas procedural finger sequence tapping skill was not affected. Our results indicate that sleep SWA enhances the capacity for encoding of declarative materials, possibly by down-scaling hippocampal synaptic networks that were potentiated towards saturation during the preceding period of wakefulness.

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