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Curr Biol. 2019 Feb 4;29(3):392-401.e4. doi: 10.1016/j.cub.2018.12.007. Epub 2019 Jan 24.

Rocking Promotes Sleep in Mice through Rhythmic Stimulation of the Vestibular System.

Author information

1
Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
2
Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; Swiss Center for Affective Science, Campus Biotech, 1202 Geneva, Switzerland.
3
Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland.
4
Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; Center for Sleep Medicine, Geneva University Hospital, 1225 Geneva, Switzerland.
5
Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland. Electronic address: paul.franken@unil.ch.

Abstract

Rocking has long been known to promote sleep in infants and, more recently, also in adults, increasing NREM sleep stage N2 and enhancing EEG slow waves and spindles. Nevertheless, whether rocking also promotes sleep in other species, and what the underlying mechanisms are, has yet to be explored. In the current study, C57BL/6J mice equipped with EEG and EMG electrodes were rocked laterally during their main sleep period, i.e., the 12-h light phase. We observed that rocking affected sleep in mice with a faster optimal rate than in humans (1.0 versus 0.25 Hz). Specifically, rocking mice at 1.0 Hz increased time spent in NREM sleep through the shortening of wake episodes and accelerated sleep onset. Although rocking did not increase EEG activity in the slow-wave and spindle-frequency ranges in mice, EEG theta activity (6-10 Hz) during active wakefulness shifted toward slower frequencies. To test the hypothesis that the rocking effects are mediated through the vestibular system, we used the otoconia-deficient tilted (tlt) mouse, which cannot encode linear acceleration. Mice homozygous for the tlt mutation were insensitive to rocking at 1.0 Hz, while the sleep and EEG response of their heterozygous and wild-type littermates resembled those of C57BL/6J mice. Our findings demonstrate that rocking also promotes sleep in the mouse and that this effect requires input from functional otolithic organs of the vestibule. Our observations also demonstrate that the maximum linear acceleration applied, and not the rocking rate per se, is key in mediating the effects of rocking on sleep.

KEYWORDS:

Otop1; linear acceleration; mechanosensory rhythmic stimulation; otolithic organs; rocking mouse model; sleep; vestibular system

PMID:
30686738
DOI:
10.1016/j.cub.2018.12.007
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