1 SLEEPJ, 2021, 1–7 doi: 10.1093/sleep/zsaa216 Advance Access Publication Date: 6 January 2021 Original Article Submitted: 16 January, 2020; Revised: 11 September, 2020 © Sleep Research Society 2021. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com. Original Article Sleep is more than rest for plasticity in the human cortex Christoph Nissen 1,2, *, Hannah Piosczyk 1 , Johannes Holz 1,3 , Jonathan G. Maier 1,2 , Lukas Frase 1, , Annette Sterr 4 , Dieter Riemann 1 and Bernd Feige 1, 1 Department of Psychiatry and Psychotherapy, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, 2 University Hospital of Psychiatry and Psychotherapy, University of Bern, Bern, Switzerland, 3 Department of Psychology, University of Applied Police Sciences Baden- Württemberg, Villingen-Schwenningen, Germany and 4 School of Psychology, University of Surrey, Guildford, Surrey, UK *Corresponding author. Christoph Nissen, Department of Psychiatry and Psychotherapy, Medical Center—University of Freiburg, Faculty of Medicine, University of Freiburg, Hauptstr. 5, 79102 Freiburg, Germany. Email: christoph.nissen@upd.ch. Abstract Sleep promotes adaptation of behavior and underlying neural plasticity in comparison to active wakefulness. However, the contribution of its two main characteristics, sleep-specifc brain activity and reduced stimulus interference, remains unclear. We tested healthy humans on a texture discrimination task, a proxy for neural plasticity in primary visual cortex, in the morning and retested them in the afternoon after a period of daytime sleep, passive waking with maximally reduced interference, or active waking. Sleep restored performance in direct comparison to both passive and active waking, in which deterioration of performance across repeated within-day testing has been linked to synaptic saturation in the primary visual cortex. No difference between passive and active waking was observed. Control experiments indicated that deterioration across wakefulness was retinotopically specifc to the trained visual feld and not due to unspecifc performance differences. The restorative effect of sleep correlated with time spent in NREM sleep and with electroencephalographic slow wave energy, which is thought to refect renormalization of synaptic strength. The results indicate that sleep is more than a state of reduced stimulus interference, but that sleep-specifc brain activity restores performance by actively refning cortical plasticity. Key words: NREM; sleep; interference; synaptic plasticity; texture discrimination; slow-wave activity Statement of signifcance We still have a limited understanding of why we sleep, and disruptions of sleep represent a prominent health problem. One fundamental question remains controversial—namely, whether sleep-specifc brain activity promotes adaptation of behavior and underlying neural plasticity (sleep hypothesis), or alternatively, whether sleep only provides a window of reduced stimulus interference passively protecting novel neural representations (rest hypothesis). Here, we used visual texture discrimination as a model of primary cortex plasticity and provide evidence that sleep is more than a state of re- duced interference, which actively restores task performance by refning underlying neural plasticity. Downloaded from https://academic.oup.com/sleep/article/44/3/zsaa216/6047280 by guest on 04 December 2023