title: Transcranial slow oscillation stimulation during NREM sleep enhances acquisition of the radial maze task and modulates cortical network activity in rats.
abstract: Slow wave sleep, hallmarked by the occurrence of slow oscillations (SO), plays an important role for the consolidation of hippocampus-dependent memories. Transcranial stimulation by weak electric currents oscillating at the endogenous SO frequency (SO-tDCS) during post-learning sleep was previously shown by us to boost SO activity and improve the consolidation of hippocampus-dependent memory in human subjects. Here, we aimed at replicating and extending these results to a rodent model. Rats were trained for 12 days at the beginning of their inactive phase in the reference memory version of the radial arm maze. In a between subjects design, animals received SO-tDCS over prefrontal cortex (PFC) or sham stimulation within a time frame of 1 h during subsequent non-rapid eye movement (NREM) sleep. Applied over multiple daily sessions SO-tDCS impacted cortical network activity as measured by EEG and behavior: at the EEG level, SO-tDCS enhanced post-stimulation upper delta (2-4 Hz) activity whereby the first stimulations of each day were preferentially affected. Furthermore, commencing on day 8, SO-tDCS acutely decreased theta activity indicating long-term effects on cortical networks. Behaviorally, working memory for baited maze arms was enhanced up to day 4, indicating enhanced consolidation of task-inherent rules, while reference memory errors did not differ between groups. Taken together, we could show here for the first time an effect of SO-tDCS during NREM sleep on cognitive functions and on cortical activity in a rodent model.
authors.affiliation: Department of Neuroendocrinology, University of Lübeck Lübeck, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Binder
authors.affiliation: Department of Neuroendocrinology, University of Lübeck Lübeck, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Rawohl
authors.affiliation: Department of Neuroendocrinology, University of Lübeck Lübeck, Germany ; Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen Tübingen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Born
authors.affiliation: Department of Neuroendocrinology, University of Lübeck Lübeck, Germany ; Graduate School for Computing in Medicine and Life Sciences, University of Lübeck Lübeck, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Marshall
keywords: EEG; consolidation; reference memory; sleep; slow oscillation stimulation; tDCS; working memory