Rockin’ and Rollin’ the Brain to Sleep –Is there a Sweet Spot of Stimulation Intensity?

Introduction: Current literature on rocking devices presents inconsistent results regarding their effect on sleep. While for humans optimal motion parameters remain unclear, efficient stimulus intensity in rodents is clearly above the vestibular perception threshold. To this end, we investigated whether stimulation intensity of passive vestibular stimulation (i.e., motion of a bed) may also play a decisive role for human sleep. Method: We report preliminary data of 13 participants (Mean age = 24.8, range 20-33). In a longitudinal within-subject design, study participants took part in four experimental sessions separated by one-week intervals. A 256-channel EEG was recorded during 93-minute-long afternoon naps taken on a bed mounted on a motion platform. In a randomized order, the bed was either motionless, moving at low intensity (i.e., above perception threshold at 6.17°/s2), or moving at high intensity (i.e., above perception threshold at 12.34°/s2). During the motion conditions, the bed moves in a sinusoidal wave pattern for 3 minutes before changing the rotation axis (e.g., from pitch to roll, from roll to yaw, etc.). Results: Preliminary descriptive analyses show a higher percentage of sleep during high-intensity (71.23%) as compared to low-intensity (57.16%) and no passive vestibular stimulation (59.64%). Specifically, enhanced N3 sleep, faster sleep onset, and reduced wake after sleep onset were observed for the high intensity compared to the low intensity and the motionless condition (15.75%, 5.69%, 10.47%; 7.08min, 16min, 12.04min; and 19.73min, 24.27min, 28.85min respectively). Conclusion: These preliminary findings suggest that passive vestibular stimulation improves the depth and efficiency of naps if applied at an intensity above the perceptual vestibular threshold level. Motion stimulation during sleep is a promising non-invasive method to promote sleep quality.