Effects of sleep inertia after daytime naps vary with executive load and time of day.

Abstract

The effects of executive load on working memory performance during sleep inertia after morning or afternoon naps were assessed using a mixed design with nap/wake as a between-subjects factor and morning/afternoon condition as a within-subject factor. Thirty-two healthy adults (mean 22.5 ± 3.0 years) attended two laboratory sessions after a night of restricted sleep (6 hrs), and at first visit, were randomly assigned to the Nap or Wake group. Working memory (n-back) and subjective workload were assessed approximately 5 and 25 minutes after 90-minute morning and afternoon nap opportunities and at the corresponding times in the Wake condition. Actigraphically assessed nocturnal sleep duration, subjective sleepiness, and psychomotor vigilance performance before daytime assessments did not vary across conditions. Afternoon naps showed shorter EEG assessed sleep latencies, longer sleep duration, and more Slow Wave Sleep than morning naps. Working memory performance deteriorated, and subjective mental workload increased at higher executive loadings. After afternoon naps, participants performed less well on more executive-function intensive working memory tasks (i.e., 3-back), but waking and napping participants performed equally well on simpler tasks. After some 30 minutes of cognitive activity, there were no longer performance differences between the waking and napping groups. Subjective Task Difficulty and Mental Effort requirements were less affected by sleep inertia and dissociated from objective measures when participants had napped in the afternoon. We conclude that executive functions take longer to return to asymptotic performance after sleep than does performance of simpler tasks which are less reliant on executive functions.

Sleep inertia, sleep homeostatic and circadian influences on higher‐order cognitive functions

“…Groeger et al . () have also shown working memory executive function to be influenced by sleep inertia following afternoon naps. Additional research is necessary to determine if other executive functions (Alvarez and Emory, ) are influenced primarily by circadian phase and test such executive functions under real world conditions (Horne and Moseley, ).…”

“…Although repeated assessments probably change cognitive processing of the task, we still observed an interference response to incongruent stimuli, suggesting that our task version provides some assessment of executive function (see Supporting information for discus-sion). Groeger et al (2011) have also shown working memory executive function to be influenced by sleep inertia following afternoon naps. Additional research is necessary to determine if other executive functions (Alvarez and Emory, 2006) are influenced primarily by circadian phase and test such executive functions under real world conditions (Horne and Moseley, 2011).…”

Procedural performance following sleep deprivation remains impaired despite extended practice and an afternoon nap

“…Sleep inertia31 in the nap condition could also, in theory, mask subsequent finger tapping improvements. The majority of our participants awoke from SWS, which has been documented to cause the highest levels of sleep inertia32.…”

Effects of Partial and Acute Total Sleep Deprivation on Performance across Cognitive Domains, Individuals and Circadian Phase

“…Each test battery lasted for approximately 40 minutes. In the main text of this paper, we report the data from the Karolinska Sleepiness Scale (KSS) [31], the Psychomotor Vigilance Task (PVT) [32], Sustained Attention Response Task (SART) [33] and verbal 1-, 2-, and 3-back tasks [29], [74]. The tasks were presented in one of the three orders fixed for each participant (Table S7).…”