• Peter Garside, Joseph Arizpe, Chi-Ieong Lau, Crystal Goh, and Vincent Walsh.
• Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK; University College London Medical School, Gower Street, London WC1E 6BT, UK.
• Brain Stimul. 2015 May 1; 8 (3): 520-7.

BackgroundSlow Wave Activity (SWA), the low frequency (<4 Hz) oscillations that characterize Slow Wave Sleep (SWS) are thought to relate causally to declarative memory consolidation during nocturnal sleep. Evidence is conflicting relating SWA to memory consolidation during nap however.Objective/HypothesisWe applied transcranial alternating current stimulation (tACS) - which, with a cross-hemispheric electrode montage (F3 and F4 - International 10:20 EEG system), is able to disrupt brain oscillations-to determine if disruption of low frequency oscillation generation during afternoon nap is causally related to disruption in declarative memory consolidation.MethodsEight human subjects each participated in stimulation and sham nap sessions. A verbal paired associate learning (PAL) task measured memory changes. During each nap period, five 5-min stimulation (0.75 Hz cross-hemispheric frontal tACS) or sham intervals were applied with 1-min post-stimulation intervals (PSI's). Spectral EEG power for Slow (0.7-0.8 Hz), Delta (1.0-4.0 Hz), Theta (4.0-8.0 Hz), Alpha (8.0-12.0 Hz), and Spindle-range (12.0-14.0) frequencies was analyzed during the 1-min preceding the onset of stimulation and the 1-min PSI's.ResultsAs hypothesized, power reduction due to stimulation positively correlated with reduction in word-pair recall post-nap specifically for Slow (P < 0.0022) and Delta (P < 0.037) frequency bands.ConclusionsThese results provide preliminary evidence suggesting a causal and specific role of SWA in declarative memory consolidation during nap.Published by Elsevier Inc.

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