Modulating overnight memory consolidation by acoustic stimulation during slow-wave sleep: a systematic review and meta-analysis

Abstract

Study objectives The low-frequency high-amplitude oscillations of slow wave sleep are considered to promote the consolidation of episodic memory. Previous research suggests that sleep slow waves can be entrained and enhanced by presenting short acoustic stimuli to the up-states of endogenous waves. Several studies have investigated the effects of these increases in slow wave activity on overnight memory consolidation, with inconsistent results. The aim of this meta-analysis was to evaluate the accumulated evidence connecting acoustic stimulation during sleep to episodic memory consolidation. Methods A systematic literature search was conducted in October 2020 using Pubmed, Web of Science and PsycInfo. Main study inclusion criteria were the application of acoustic slow wave enhancement in healthy participants and an assessment of pre- and post-sleep episodic memory performance. Effect sizes were pooled using a random effects model. Results Ten primary studies with 11 experiments and 177 participants were included. Results showed a combined effect size (Hedges’ g) of 0.25 (p=0.07). Subgroup models based on young adults (n = 8), phase-locked stimulation approaches (n = 8) and their combination (n = 6) showed combined effect sizes of 0.31 (p=0.051), 0.36 (p=0.047) and 0.44 (p=0.01), respectively. There was no indication of publication bias or bias in individual studies. Conclusions Acoustic enhancement of slow wave sleep tends to increase the overnight consolidation of episodic memory but effects remain small and - with the exception of subgroup models - at trend levels. Currently, the evidence is not sufficient to recommend the use of commercially available devices.

Translational approaches to influence sleep and arousal

“…Many people use white noise or recordings of natural sounds such as rain to facilitate falling asleep, although the evidence for its effectiveness appears weak ( Riedy et al, 2021 ). Auditory stimulation is a non-invasive method that can influence sleep since investigators are able to use rhythmic acoustic stimuli or stimuli timed to the phase of ongoing sleep oscillations to influence sleep architecture ( Bellesi et al, 2014 ; Malkani and Zee, 2000)( Wunderlin et al, 2021 ). In auditory stimulation, subjects listen to sound stimuli which have been specifically tailored to cause a change in neural activity while and/or before they fall asleep.…”

“…Auditory stimuli are very effective in inducing K complexes and slow oscillations during NREM and the majority of auditory stimulation studies have been targeted to increase slow wave activity or spindle-slow wave complexes ( Malkani and Zee, 2020 ). However, auditory stimulation can also be tailored to induce sleep spindles at specific frequencies ( Antony and Paller, 2017 ) or to induce PGO waves during REM sleep ( Bellesi et al, 2014 ; Malkani and Zee, 2020 ; Wunderlin et al, 2021 ).…”

Effects of auditory sleep modulation approaches on brain oscillatory and cardiovascular dynamics

“…Over the last few years, especially auditory stimulation has emerged as a promising, non-invasive, and feasible approach to selectively modulate slow waves during deep sleep (Besedovsky et al, 2017;Grimaldi et al, 2019; Hong-Viet V. Ngo, Martinetz, et al, 2013). However, various stimulation protocols exist, leading to inconsistent findings on behavioral outcomes (e.g., reviewed in (Wunderlin et al, 2021)) and comparisons of those approaches on efficacy to selectively enhance or decrease slow waves are missing. Ngo and colleagues (Hong-Viet V. Ngo, Martinetz, et al, 2013) were the first to report that targeting the ascending up-phase of ongoing slow waves seems to be important to elicit improvements in overnight memory consolidation.…”

Wearing an Eye Mask During Overnight Sleep Improves Episodic Learning and Alertness

“…Non-pharmacological methods for improving sleep are a topic of great current interest (Wunderlin et al, 2021), and the use of an eye mask to prevent light from reaching the retina during overnight sleep has been demonstrated to positively affect subjective sleep quality in intensive care patients who are systematically exposed to high levels of light (Bani Younis et al, 2019;Locihová et al, 2018). In the current study, we set out to investigate the benefits of preprint (which was not certified by peer review) is the author/funder.…”