Heart rate variability during daytime naps as a predictor of memory consolidation in healthy, well-rested adults
Abstract
Abstract: Insufficient sleep is associated with a range of health outcomes including poor cardiovascular function and decreased cognitive performance. Heart rate variability (HRV) is a reliable technique to evaluate autonomic activity and shows marked stereotypic changes across a night of sleep. Previous findings report an overall reduction in cardiovascular output during non-rapid eye movement sleep (NREM), which has been associated with health benefits. However, it is not know whether these changes in autonomic activity play a role in memory function. We propose to investigate the role of autonomic function in memory consolidation by examining how the fluctuations in cardiovascular output during sleep are related to sleep-dependent memory consolidation. We will specifically examine this question in the framework of daytime sleep (i.e., naps) that 1) are used by many to supplement nighttime sleep, 2) show the same cognitive benefits as nighttime sleep, and 3) have better translational significance. Surprisingly little is known about cardiovascular output during naps. Therefore Aim 1 will assess HRV during naps, specifically measuring changes across each sleep stage, and comparing the dynamics and magnitudes of change between nighttime sleep and daytime naps. Subjects will spend one nap and one night in the sleep lab with polysomnography, including electrocardiography (ECG), as well as five minutes of pre-nap waking ECG. We will measure inter-beat intervals, total power, low frequency power (.04-.15 Hz), and high frequency power (.15-.40 Hz) components of HRV during pre-sleep wakefulness, NREM and rapid eye movement (REM) sleep. We hypothesize that we will find similar HRV patterns during daytime sleep as previously reported for nocturnal sleep. Aim 2 will investigate the role of HRV fluctuations in naps in memory consolidation across a wide range of memory domains that are each supported by separate brain areas. During this study we will also assess whether changes in HRV and memory consolidation is correlated with a neurotransmitter associated with autonomic function (i.e., norepinephrine). We will measure a range of memory tasks before and after a PSG-recorded nap, plus we will measure levels of norepinephrine. For this aim, we hypothesize that we will find correlations between parasympathetic activity during NREM and REM sleep with memory improvement, and that this relationship will be moderated by norepinephrine. Aim 3 will take a translational approach by testing a series of offthe- shelf devices to measure HRV during sleep and wake to investigate whether we can observe the same measurements and effects of HRV without the cumbersome sleep lab approach. We will utilize ambulatory activity and heart monitors to assess sleep/wake and HRV and correlate these with performance changes in memory tasks. Findings from these studies will make an important contribution to our understanding of the role of the autonomic system on sleep and cognition, an area that has received very little attention. In light of the ongoing debate surrounding the health benefits and/or risks associated with napping, these results will also specify the relationship between napping and cardiovascular health in young, healthy adults.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512699
Entities
People
- Sara Mednick
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents