Autonomic Activity during a Daytime Nap Facilitates Working Memory Improvement

Abstract

Recent investigations have implicated the parasympathetic branch of the autonomic nervous system in higher-order executive functions. These actions are purported to occur through autonomic nervous system's modulation of the pFC, with parasympathetic activity during wake associated with working memory (WM) ability. Compared with wake, sleep is a period with substantially greater parasympathetic tone. Recent work has reported that sleep may also contribute to improvement in WM. Here, we examined the role of cardiac parasympathetic activity during sleep on WM improvement in healthy young adults. Participants were tested in an operation span task in the morning and evening, and during the intertest period, participants experienced either a nap or wake. We measured high-frequency heart rate variability as an index of cardiac, parasympathetic activity during both wake and sleep. Participants showed the expected boost in parasympathetic activity during nap, compared with wake. Furthermore, parasympathetic activity during sleep, but not wake, was significantly correlated with WM improvement. Together, these results indicate that the natural boost in parasympathetic activity during sleep may benefit gains in prefrontal executive function in young adults. We present a conceptual model illustrating the interaction between sleep, autonomic activity, and prefrontal brain function and highlight open research questions that will facilitate understanding of the factors that contribute to executive abilities in young adults as well as in cognitive aging.

Competitive dynamics underlie cognitive improvements during sleep

“…However, not all studies report a consistent association between SOs and WM [13,36,37], and few accounts for autonomic activity. Chen and colleagues reported that vagal activity during SWS was a better predictor of WM improvement than SWA or vagal activity during wake [19]. In the current work, we found that changes in vagal autonomic activity during SWS, but not SOs per se, was critical for WM performance improvement.…”

“…Recent studies have shown that WM improvement only occurs when the interval between training sessions contains nocturnal (Zinke et al, 2018;Kuriyama et al, 2008) or daytime sleep (Lau et al, 2015). Given that NREM sleep is a period of vagal dominance compared with wake, a recent study identified vagal HF HRV during NREM as a strong predictor of WM improvement (Chen, Whitehurst, et al, 2020a).…”

Age‐related losses in cardiac autonomic activity during a daytime nap

“…These studies support the notion that naps, like nighttime sleep, may serve as a mini-cardiovascular break. Further, and aligned with the Neurovisceral Integration Model, studies have shown that parasympathetic activity during a daytime nap facilitates improvement in long-term memory (Whitehurst et al, 2016) and working memory (Chen et al, 2020a). Furthermore, these previous investigations did not directly address whether cardiovascular benefits during a nap are sleep-specific or whether benefits can also be achieved from a comparable duration of quiet wake during the day.…”

Autonomic/Central Coupling during Daytime Sleep Differs between Older and Younger People

“…The interplay between the heart and brain has been identified during sleep at both broad and specific-feature levels. Broadly for example, each sleep stage is characterized by a specific EEG and ANS profile, with greater overall parasympathetic activity (HF-HRV) during NREM compared to waking or REM [5,8,9,11]. Brandenburger et al (2001) also found that as slow waves dissipated with reducing homeostatic sleep pressure across the night, LF/HF HRV rose, suggesting an inverse relationship between the two.…”

“…Cardiac vagal activity, as measured by high frequency heart rate variability (HF HRV: 0.14 -0.4Hz), is a traditional measure of parasympathetic activity [30]. Greater HF HRV during wake is related to better physical health and emotion regulation, and recent evidence links HF HRV during sleep to enhanced memory [1,9,10,52]. In young, healthy people, a balance exists between activity in the sympathetic and parasympathetic branches, moving from a sympathetic-dominant state during wakefulness to parasympathetic dominant state during NREM sleep [5,8,9,20,51].…”