Selective REM sleep restriction in mice using a device designed for tunable somatosensory stimulation.

BACKGROUND: Sleep perturbation is widely used to investigate the physiological mechanisms that mediate sleep-wake dynamics, and to isolate the specific roles of sleep in health and disease. However, state-of-the-art methods to accomplish sleep perturbation in preclinical models are limited in their throughput, flexibility, and specificity. NEW METHOD: A system was developed to deliver vibro-tactile somatosensory stimulation aimed at controlled, selective sleep perturbation. The frequency and intensity of stimulation can be tuned to target a variety of experimental applications, from sudden arousal to sub-threshold transitions between light and deep stages of NREM sleep. This device was activated in closed-loop to selectively interrupt REM sleep in mice. RESULTS: Vibro-tactile stimulation effectively and selectively interrupted REM sleep - significantly reducing the average REM bout duration relative to matched, unstimulated baseline recordings. As REM sleep was repeatedly interrupted, homeostatic mechanisms prompted a progressively quicker return to REM sleep. These effects were dependent on the parameters of stimulation applied. COMPARISON WITH EXISTING METHODS: Existing sleep perturbation systems often require moving parts within the cage and/or restrictive housing. The system presented is unique in that it interrupts sleep without invading the animal's space. The ability to vary stimulation parameters is a great advantage over existing methods, as it allows for adaptation in response to habituation and/or circadian/homeostatic changes in arousal threshold. CONCLUSIONS: The proposed method of stimulation demonstrates feasibility in affecting mouse sleep within a standard home cage environment, thus limiting environmental stress. Furthermore, the ability to tune frequency and intensity of stimulation allows for graded control over the extent of sleep perturbation, which potentially expands the utility of this technology beyond applications related to sleep.

A comparative study of sleep and diurnal patterns in house mouse (Mus musculus) and Spiny mouse (Acomys cahirinus).

Most published sleep studies use three species: human, house mouse, or Norway rat. The degree to which data from these species captures variability in mammalian sleep remains unclear. To gain insight into mammalian sleep diversity, we examined sleep architecture in the spiny basal murid rodent Acomys cahirinus. First, we used a piezoelectric system validated for Mus musculus to monitor sleep in both species. We also included wild M. musculus to control for alterations generated by laboratory-reared conditions for M. musculus. Using this comparative framework, we found that A. cahirinus, lab M. musculus, and wild M. musculus were primarily nocturnal, but exhibited distinct behavioral patterns. Although the activity of A. cahirinus increased sharply at dark onset, it decreased sharply just two hours later under group and individual housing conditions. To further characterize sleep patterns and sleep-related variables, we set up EEG/EMG and video recordings and found that A. cahirinus sleep significantly more than M. musculus, exhibit nearly three times more REM, and sleep almost exclusively with their eyes open. The observed differences in A. cahirinus sleep architecture raise questions about the evolutionary drivers of sleep behavior.

Tunable somatosensory stimulation for selective sleep restriction studies in rodents.

Many methods for sleep restriction in rodents have emerged, but most are intrusive, lack fine control, and induce stress. Therefore, a versatile, non-intrusive means of sleep restriction that can alter sleep in a controlled manner could be of great value in sleep research. In previous work, we proposed a novel system for closed-loop somatosensory stimulation based on mechanical vibration and applied it to the task of restricting Rapid Eye Movement (REM) sleep in mice [1]. While this system was effective, it was a crude prototype and did not allow precise control over the amplitude and frequency of stimulation applied to the animal. This paper details the progression of this system from a binary, "all-or-none" version to one that allows dynamic control over perturbation to accomplish graded, state-dependent sleep restriction. Its preliminary use is described in two applications: deep sleep restriction in rats, and REM sleep restriction in mice.