Abstract
Sleep is regulated in a time-of-day dependent manner and profits working memory. However, the impact of the circadian timing system as well as contributions of specific sleep properties to this beneficial effect remains largely unexplored. Moreover, it is unclear to which extent inter-individual differences in sleep-wake regulation depend on circadian phase and modulate the association between sleep and working memory. Here, sleep electroencephalography (EEG) was recorded during a 40-h multiple nap protocol, and working memory performance was assessed by the n-back task 10 times before and after each scheduled nap sleep episode. Twenty-four participants were genotyped regarding a functional polymorphism in adenosine deaminase (rs73598374, 12 G/A-, 12 G/G-allele carriers), previously associated with differences in sleep-wake regulation. Our results indicate that genotype-driven differences in sleep depend on circadian phase: heterozygous participants were awake longer and slept less at the end of the biological day, while they exhibited longer non rapid eye movement (NREM) sleep and slow wave sleep concomitant with reduced power between 8–16 Hz at the end of the biological night. Slow wave sleep and NREM sleep delta EEG activity covaried positively with overall working memory performance, independent of circadian phase and genotype. Moreover, REM sleep duration benefitted working memory particularly when occurring in the early morning hours and specifically in heterozygous individuals. Even though based on a small sample size and thus requiring replication, our results suggest genotype-dependent differences in circadian sleep regulation. They further indicate that REM sleep, being under strong circadian control, boosts working memory performance according to genotype in a time-of-day dependent manner. Finally, our data provide first evidence that slow wave sleep and NREM sleep delta activity, majorly regulated by sleep homeostatic mechanisms, is linked to working memory independent of the timing of the sleep episode within the 24-h cycle.
Highlights
The quantity and quality of sleep majorly depends on its timing
In the light of the strong circadian regulation of rapid eye movement (REM) sleep duration (e.g., [20]), we considered in a step if the genotype-dependent impact of REM sleep duration on working memory (WM) accuracy improvements is dependent on circadian phase
Our study suggests that the circadian regulation of sleep differs according to the adenosine deaminase (ADA) polymorphism, with the most prominent group differences during maximal circadian wake and sleep promotion
Summary
The quantity and quality of sleep majorly depends on its timing. During the biological night (i.e., during phases of melatonin secretion), the human circadian pacemaker facilitates sleep initiation and preservation, while it actively promotes wakefulness during the biological day [1, 2]. The overall regulation of the sleep-wake cycle by circadian and homeostatic factors exhibits large and stable inter-individual differences, which can partially be traced back to genetic variations such as the c.22G.A polymorphism (rs73598374) located in the gene encoding adenosine deaminase (ADA; [7, 8]). This polymorphism acts on sleep-wake regulation most likely through genotype-specific differences in the ADA-dependent metabolization of adenosine [9,10,11,12,13], which is involved in the regulation of sleep homeostasis [14]. We recently gathered first evidence that the circadian timing system varies according to the ADA polymorphism, since G/A-allele carriers exhibited a later onset of melatonin secretion [17], mirroring a shift in the opening of the gate for sleep [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
