Functional Magnetic Resonance Imaging Sleep Study With Auditory Stimuli

Objective Electroencephalography is generally considered the gold standard for defining sleep, but, in fact, sleep is a behavior and is defined by widely accepted behavioral characteristics like auditory arousal threshold. Electroencephalography merely became a surrogate for the behavioral definition when, in the first electroencephalographic sleep studies, researchers discovered a strong correlation between electroencephalographic slow waves and auditory arousal thresholds. With the advent of functional magnetic resonance imaging, one would expect the first sleep studies that used this new measure would have been designed to correlate it with auditory arousal threshold. However, these studies have never been conducted. This protocol will fill this gap in the literature. We hypothesize that undiscovered patterns of brain activity or functional connectivity exist during sleep and that an approach that defines sleep behaviorally will expose these patterns. Study Population The subject group in this study will be young, healthy individuals with excellent sleep health. Choosing this subject group will maximize the probability that subjects will sleep during all-night functional magnetic resonance imaging. Our target number of completers was 12 for the pilot study, was 43 for the main study, and is 85 for the normative study. Design After a one-week home-monitoring period that includes a regular in-to-bed and out-of-bed time, subjects will undergo two all-night functional magnetic resonance imaging sleep studies separated by a one-week washout period with continued home monitoring. The first night will serve as an adaptation night, which is known to reduce the sleep alterations that accompany sleeping in a laboratory environment. We will measure sleep depth behaviorally by arousing subjects with auditory stimuli that progressively increase in intensity. This procedure will be performed approximately eight times per night. The timing of the arousals will be distributed randomly across the night. Data Generated The data generated will be auditory arousal thresholds and the preceding brain activity and functional connectivity derived from functional magnetic resonance imaging.