Transcranial Current Stimulation During Sleep Facilitates Insight into Temporal Rules, but does not Consolidate Memories of Individual Sequential Experiences

Abstract

Slow-wave sleep (SWS) is known to contribute to memory consolidation, likely through the reactivation of previously encoded waking experiences. Contemporary studies demonstrate that when auditory or olfactory stimulation is administered during memory encoding and then reapplied during SWS, memory consolidation can be enhanced, an effect that is believed to rely on targeted memory reactivation (TMR) induced by the sensory stimulation. Here, we show that transcranial current stimulations (tCS) during sleep can also be used to induce TMR, resulting in the facilitation of high-level cognitive processes. Participants were exposed to repeating sequences in a realistic 3D immersive environment while being stimulated with particular tCS patterns. A subset of these tCS patterns was then reapplied during sleep stages N2 and SWS coupled to slow oscillations in a closed-loop manner. We found that in contrast to our initial hypothesis, performance for the sequences corresponding to the reapplied tCS patterns was no better than for other sequences that received stimulations only during wake or not at all. In contrast, we found that the more stimulations participants received overnight, the more likely they were to detect temporal regularities governing the learned sequences the following morning, with tCS-induced beta power modulations during sleep mediating this effect.

A model of bi-directional interactions between complementary learning systems for memory consolidation of sequential experiences

“…). If instead the items were randomly chosen to cue replays and the activation always spread in one direction to the end of the sequence, the weights of the later links would grow stronger than the earlier links since they are more likely to be adapted over the course of many replays (Lerner et al, 2019 ).…”

One-Shot Tagging During Wake and Cueing During Sleep With Spatiotemporal Patterns of Transcranial Electrical Stimulation Can Boost Long-Term Metamemory of Individual Episodes in Humans

“…A potential strategy is to employ SW tACS to boost SWOs (Jones et al, 2018;Ketz et al, 2018) in alternating blocks with STAMPs. However, our recent attempt at this strategy failed to boost the consolidation of individual sequential experiences (Lerner et al, 2019). Potential reasons for the failure include a much smaller sample size for a between-subjects design (N = 12), the usage of a hybrid task with both procedural and declarative memory elements, the presence of a hidden temporal regularity shared across all sequence types, and mutual interference between specific STAMPs and non-specific SW tACS.…”

Manipulating neural activity and sleep-dependent memory consolidation

“…W, Wake. The asterisks indicate significant differences: *, p < 0.05; **p < 0.01. between learning and stimulation (Lu et al, 2018;Miyamoto et al, 2016), subjects' cognitive ability (Koo et al, 2018), different processing demands of the learning material, and/ or differences in NREM sleep stage composition at the time of stimulation (Dehnavi et al, 2019;Jiang et al, 2019;Lerner et al, 2019; Figure 2). For example, when, after learning a list of word pairs, subjects are instructed to forget correspondingly cued words (motivated forgetting), the relation of post-task spindle density during light versus deep NREM sleep differed as compared to a control condition (Figure 2).…”