Abstract
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.
Highlights
Memory consolidation is a process whereby new memories are integrated into a pre-existing stable network of long-term associations [1]
We sought to determine if slow wave activity (SWA) e slow oscillatory (0.7e0.8 Hz) and delta activity (1.0e4.0 Hz) e has a causal influence on declarative memory consolidation by measuring memory changes resulting from disruption of SWA
SWA during afternoon nap correlated with declarative memory performance
Summary
Memory consolidation is a process whereby new memories are integrated into a pre-existing stable network of long-term associations [1]. It is believed that during SWS, slow oscillations temporally coordinate hippocampal and thalamic brain activity during the depolarizing up-state of the oscillation This hippocampalneocortical dialog is thought to underly the transfer of information between brain structures and their memory systems [8,9]. Slow Wave Activity (SWA), the low frequency (
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