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Sleep and sensory stimulations

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Defense Thèse de privat-docent : Univ. Genève, 2021
Abstract We sleep about 30 % of our lifetime and this mysterious behavior that leads the individual to an unconsciousness state is indispensable to the survey of all species. Sleep is not a homogeneous state of passive rest but is composed of two different sub-states; the Non-rapid eyes movements (NREM) sleep and the REM sleep. These states are characterized by specific and distinctive features events on electroencephalography (EEG) recordings (i.e. sleep spindles and slow oscillations (SOs) are specific of NREM). These features result from the regulation of the complex brain circuitries of the vigilance states, which influence thalamocortical activity that in turn generates brain oscillations. While sleep functions are still under debate, a strong correlation is observed between NREM sleep and declarative memory consolidation. Recent experimental evidences suggest that during NREM sleep memory traces are reactivated and transferred from a temporary storage in the hippocampus to a long-term storage in cortical networks. Mechanistically, the occurrence and interactions of three cardinal sleep rhythms (cortical SOs, thalamic sleep spindles and hippocampal sharp-waves ripples) are critical to induce plasticity mechanisms underlying memory consolidation. Slow waves activities and sleep spindles of NREM sleep ensure a good quality of sleep, protecting from sleep distractors (e.g. noisy environments) as well as improving daytime functioning and memory performances. This knowledge has now opened a new research field that tries to develop approaches to modulate brain oscillations using frequency specific entrainment by external sensory stimulations in order to improve sleep and memory retention. In this context, and because it is believed since immemorial time that rocking affects sleep, we decided to study the effects of a continuous repetitive rocking stimulation on sleep architecture and memory. This privat-docent manuscript presents three of my studies that focus on this question across interdisciplinary projects in human and mouse models. Using scalp EEG, we showed that a repetitive, lateral, gentle rocking motion (0.25Hz) applied during sleep facilitates entrance into sleep, reduces nighttime awakenings, increases time spent in deep sleep and is associated with a boost in the synchronized neural activities of the thalamo-cortical networks (i.e. SOs and spindles) that are believed to play an important role memory consolidation. In our mouse study, we demonstrated that these rocking effects are mediated by the sensory system of balance and spatial orientation located in the inner ear, i.e. the vestibular system. In conclusion, slow rocking stimulation improves the sleep quality and contributes to promote cognitive functions. Based on these promising findings, our ongoing and future studies aim to explore the possible therapeutic options for subjects with sleep problems such as insomnia or for aging people who frequently suffer from poor sleep and memory impairments.
Keywords SleepSensory stimulationsVestibular
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Research group Neuroimagerie du Sommeil et de la Cognition (832)
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BAYER, Laurence. Sleep and sensory stimulations. Université de Genève. Thèse de privat-docent, 2021. doi: 10.13097/archive-ouverte/unige:163014 https://archive-ouverte.unige.ch/unige:163014

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Deposited on : 2022-09-02

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