Closed-loop auditory stimulation of sleep slow oscillations: basic principles and best practices

Abstract

Sleep is an indispensable part of our life and plays a critical role in our physical and mental well-being. During sleep, despite the paucity of behavior, our brain stays active and exhibits a wide range of coupled brain oscillations. This activity in sleep-characteristic brain oscillations has been linked to various functions of sleep. However, whether these sleep oscillations mediate these functions or reflect mere epiphenomena is not yet fully understood. To disentangle the causality of these relationships, experiments utilizing non-invasive stimulation techniques have been essential. In particular, auditory stimulation aligned with neural activity in a closed-loop controlled fashion has drawn increasing attention during the last years due to its specificity and practical advantages. In this review, we summarize closed-loop auditory stimulation experiments that generated evidence to support a causal role of slow oscillations in information reprocessing functions of sleep. Furthermore, we provide technical details and guidelines regarding best practices in closed-loop auditory stimulation, from how to perform the stimulation to analysis strategies. Besides discussing important caveats and open questions, we also touch on various areas in which closed-loop auditory stimulation is applicable, from fundamental investigations on memory processing and endocrine function, to its potential for clinical applications. Eventually, we propose potential topics for future research.

Sleep functional connectivity, hyperexcitability, and cognition in Alzheimer's disease

“…There is growing interest in developing treatments that increase gamma activity in the awake state (eg, via gamma entrainment 71,72 or transcranial magnetic stimulation 73,74 ) or that increase slow-wave activity during sleep. [75][76][77] Our results suggest that tailoring network modulation strategies uniquely across the sleep-wake cycle and that gauging the effects of network modulation on both awake and asleep states may be important for optimizing these therapeutic outcomes in AD.…”

Highly effective verified lucid dream induction using combined cognitive-sensory training and wearable EEG: a multi-centre study

“…Also, while the few existing studies using sensory stimulation for LD induction employed openloop techniques (Antony et al, 2022;Esfahani, Farboud, et al, 2023), future work may also employ a closed-loop stimulation approach by taking the temporal dynamics of the EEG signal into account to enhance the efficacy of REM stimulation targeting (Harrington et al, 2021). This closed-loop method would also prove beneficial in preventing stimulation during instances of low signal-to-noise ratio, as well as when signs of arousal are present.…”