Nap Condition Research Articles

No effect of napping on episodic foresight and prospective memory in kindergarten children

SummaryPreschool children often have problems in remembering to carry out a planned behaviour. This study investigated the impact of napping on episodic foresight (planning for future events) and prospective memory (remembering to perform an action in the future) in 2–3‐year‐old children. In a quasi‐experimental design, we compared children who napped (nap condition, n = 20) after receiving information about an upcoming problem (episodic foresight task) and a delayed intention (prospective memory task) with those who stayed awake (wake condition, n = 43). We hypothesised that napping would improve performance in the episodic foresight and the prospective memory tasks. Contrary to the hypothesis, napping did not significantly affect children's episodic foresight or prospective memory performance, even after controlling for the group difference in age. Task performance was primarily explained by memory effects and age. Further research that incorporates stricter controls and evaluates pre‐nap memory strength is necessary fully to elucidate the complex interplay between napping, age, episodic foresight, and prospective memory performance in young children.

Post-Lunch Napping as a Strategy to Enhance Physiological Performance and Cognitive Function in Elite Volleyball Players

Background and Objectives: Volleyball demands high levels of anaerobic strength, flexibility, agility, and mental focus. Adequate sleep has been shown to enhance athletic performance and cognitive function. This study investigates the impact of post-lunch naps of varying durations (25 and 45 min) on the physiological performance and cognitive focus of elite volleyball players. Materials and Methods: Sixteen elite volleyball players (8 male, 8 female) with at least 7 years of competitive experience participated in a randomized crossover study. They underwent three experimental conditions: no nap (No-Nap), a 25-min nap (N25), and a 45-min nap (N45). Physical performance was measured through counter-movement jumps (CMJ) and volleyball agility tests, while cognitive function was assessed using the D2 attention test. Statistical analysis included repeated measures ANOVA to examine the differences between nap conditions and gender-specific responses. Results: Significant improvements in both physical performance and cognitive focus were observed in the N25 and N45 conditions compared to the No-Nap condition (indicating the effectiveness of short naps in enhancing both physical and mental performance). Males outperformed females in most physical metrics, while females scored higher on the D2 attention test (suggesting possible gender-specific responses to napping). The 25-min nap showed slightly better results in terms of sleep quality and subsequent performance (confirming that shorter naps may be more beneficial). Conclusions: Post-lunch naps, especially of 25 or 45 min, enhance both physiological and cognitive performance in elite volleyball players. These findings suggest that integrating short naps into athletes’ training regimens can improve performance and focus, with potential gender-specific benefits. Further research is needed to explore long-term effects and variations across other sports.

Enhancing Anaerobic Performance in Kickboxers: The Strategic Role of Short-Duration Napping

The intricate relationship between sleep and athletic performance has long been a subject of interest in sports science. This study delves into the specific impact of short-duration napping on anaerobic performance parameters in the study of kickboxing, an intense combat sport demanding both physical prowess and strategic acumen. We conducted a controlled investigation with 14 young elite male kickboxers, characterized by an average age of 20.29 ± 0.80 years, a height of 174.48 ± 4.11 cm, body masses of 70.46 ± 7.78 kg, and a body mass index (BMI) of 23.12 ± 2.02 kg/m². The experimental design encompassed three distinct conditions: no napping (N0), a 25-minute nap (N25), and a 45-minute nap (N45). The evaluation focused on several key performance metrics, including countermovement jump (CMJ), mean power, and peak power outputs. Intriguingly, our findings indicated that while CMJ values remained relatively unaffected by the napping conditions, significant variations were observed in both mean and peak power outputs, particularly among participants who napped. These variations suggest that napping, even for short durations, can significantly influence certain anaerobic performance parameters in kickboxers, with a marked improvement in power-related aspects. This research contributes to the expanding body of literature on the role of sleep and rest in athletic performance, specifically highlighting the potential of napping as an effective strategy for enhancing physical capabilities in combat sports. The implications of these findings extend beyond the realm of kickboxing, offering valuable insights and practical applications for athletic training and performance optimization across various sports disciplines where anaerobic capabilities are crucial.

A 90- followed by a 30-min nap reduces fatigue whereas a 30- followed by a 90-min nap maintains cognitive performance in night work: A randomized crossover-pilot study

ObjectiveTo investigate the effects of combinations of brief naps (a 90- followed by a 30-min nap vs. a 30- followed by a 90-min nap) on sleep inertia, reducing sleepiness and fatigue, and maintaining performance during night hours. MethodsThis randomized, comparative, repeated-measure, cross-over study investigated subjective and cognitive performance in 12 healthy females, evaluated in three experimental nap conditions: 1) from 22:30 to 00:00 and 02:30 to 03:00 (Pre90-NAP group), 2) from 23:30 to 00:00 and 02:30 to 04:00 (Pre30-NAP) group, and 3) no naps (NO-NAP group). Participants’ body temperature, psychomotor vigilance task (PVT) and Uchida-Kraepelin test (UKT) scores, and subjective feelings of drowsiness and fatigue were evaluated. Sleep state was determined by an actigraphy monitoring device worn by participants. ResultsRegardless of timing, both 90-min naps were associated with sleep inertia, and both 30-min naps with minimal sleep inertia. Reaction times were shorter and fewer errors were committed at 2 h post-nap in the Pre30-NAP and Pre90-NAP groups compared with those at the same time in the NO-NAP group. Adding a 90-min nap to a 30-min nap reduced subjective fatigue and shortened reaction times, and adding a 30-min nap to a 90-min nap was effective in maintaining performance, suggesting a synergistic effect. ConclusionsTaking two naps during a night work can mitigate sleepiness and fatigue, and maintain performance. A 90- followed by a 30-min nap reduced fatigue and reaction time, and a 30- followed by a 90-min nap maintained cognitive performance in the early morning.

Spindle-slow wave coupling and problem-solving skills: impact of age.

We examined how aging affects the role of sleep in the consolidation of newly learned cognitive strategies. Forty healthy young adults (20-35 years) and 30 healthy older adults (60-85 years) were included. Participants were trained on the Tower of Hanoi (ToH) task, then, half of each age group were assigned to either the 90-minute nap condition, or stayed awake, before retesting. The temporal co-occurrence between slow waves (SW) and sleep spindles (SP) during non-rapid eye movement sleep was examined as a function of age in relation to memory consolidation of problem-solving skills. We found that despite intact learning, older adults derived a reduced benefit of sleep for problem-solving skills relative to younger adults. As expected, the percentage of coupled spindles was lower in older compared to younger individuals from control to testing sessions. Furthermore, coupled spindles in young adults were more strongly coupled to the SW upstate compared to older individuals. Coupled spindles in older individuals were lower in amplitude (mean area under the curve; μV) compared to the young group. Lastly, there was a significant relationship between offline gains in accuracy on the ToH and percent change of spindles coupled to the upstate of the slow wave in older, but not younger adults. Multiple regression revealed that age accounted for differences in offline gains in accuracy, as did spindle coupling during the upstate. These results suggest that with aging, spindle-slow wave coupling decreases. However, the degree of the preservation of coupling with age correlates with the extent of problem-solving skill consolidation during sleep.

Effect of homeostatic pressure and circadian arousal on the storage and executive components of working memory: Evidence from EEG power spectrum

Diurnal fluctuations in working memory (WM) performance, characterized by task-specific peaks and troughs, are likely attributed to the differential regulation of WM subcomponents by interactions between circadian and homeostatic processes. The current study aimed to investigate the independent effects of circadian and homeostatic processes on the storage and executive subcomponents of WM. We assessed the change in frontal-midline theta (FMT) power supporting WM executive component and posterior alpha/beta power supporting WM storage during N-back tasks in the morning, midafternoon with and without a nap from 31 healthy adults. The results suggested that when the accumulated sleep homeostasis was alleviated in the midafternoon by a daytime nap, higher ACC, less number of omissions, and a stronger increase in FMT power from the no nap to nap conditions. Compared to the morning, a stronger decrease in posterior alpha power, and posterior beta power (only in the 3-back task), was observed in the no-nap condition because of circadian arousal regulation. These findings suggest that the circadian process primarily influences the storage aspect of WM supported by posterior alpha and beta activity, while sleep homeostasis has a greater impact on the execution aspect supported by FMT activity.

Developmental changes in retention and generalization of nonadjacent dependencies over a period containing sleep in 18-mo-old infants.

Sleep promotes the stabilization of memories in adulthood, with a growing literature on the benefits of sleep for memory in infants and children. In two studies, we examined the role of sleep in the retention and generalization of nonadjacent dependencies (NADs; e.g., a-X-b/c-X-d phrases) in an artificial language. Previously, a study demonstrated that over a delay of 4 h, 15 mo olds who nap after training retain a general memory of the NAD rule instead of memory for specific NADs heard during training. In experiment 1, we designed a replication of the nap condition used in the earlier study but tested 18-mo-old infants. Infants of this age retained veridical memory for specific NADs over a delay containing sleep, providing preliminary evidence of the development of memory processes (experiment 1). In experiment 2, we tested 18 mo olds' ability to generalize the NAD to new vocabulary, finding only infants who napped after training generalized their knowledge of the pattern to completely novel phrases. Overall, by 18 mo of age, children retain specific memories over a period containing sleep, and sleep promotes abstract memories to a greater extent than wakefulness.

Effect of Short versus Long Duration Naps on Blood Pressure during Simulated Night Shift Work: A Randomized Crossover Trial

Objective Blunting of the sleep-related dip in blood pressure (BP) has been linked to numerous cardiovascular outcomes including myocardial infarction. Blunting of BP dipping occurs during night shift work and previous research suggest that a 60-min or longer on-shift nap is needed to restore normal/healthy BP dipping. We sought to determine the effect of different durations of napping on BP during and following simulated night shifts. We hypothesized that the greatest benefit in terms of restoration of normal BP dipping during night shift work would be observed during a longer duration nap versus a shorter nap opportunity. Methods We used a randomized crossover laboratory-based study design. Participants consented to complete three separate 72-hr conditions that included a 12-hr simulated night shift. Nap conditions included a 30-min and 2-hr nap compared to a no-nap condition. Ambulatory BP monitoring was assessed hourly and every 10-30 mins during in-lab naps. Blunted BP dipping during in-lab naps was the primary outcome. Goal enrollment of 25 (35 with attrition) provided 80% power to detect a mean difference of 5 mmHg in BP between nap conditions. Results Of the 58 screened, 28 were consented, and 26 completed all three 72-hr conditions. More than half (53.6%) were female. Mean age was 24.4 years (SD7.2). Most (85.7%) were certified as emergency medical technicians or paramedics. The mean percentage dip in systolic BP (SBP) and diastolic BP (DBP) did not differ between the 30-min and 2-hr nap conditions (p > 0.05), yet a greater proportion of participants experienced a 10-20% dip in SBP or DBP during the 2-hr nap versus the 30-min nap (p < 0.05). For every additional minute of total sleep during the 30-min nap, the percentage of SBP dip improved by 0.60%, and the percentage of DBP dip improved by 0.68% (p < 0.05). These improvements approximate to a 6% per minute relative advancement toward normal/healthy BP dipping. Conclusions Restoration of a normal/healthy dip in BP is achievable during short and long duration nap opportunities during simulated night shift work. Our findings support the hypothesis that BP dipping is more common during longer 2-hr versus shorter 30-min naps. Trial registration ClinicalTrials.gov, NCT04469803. Registered on 9 July 2020.

Are Short Duration Naps Better than Long Duration Naps for Mitigating Sleep Inertia? Brief Report of a Randomized Crossover Trial of Simulated Night Shift Work

Objective We sought to test the effects of different duration naps on post-nap cognitive performance during simulated night shifts. Methods We used a randomized laboratory-based crossover trial design with simulated 12-hr night shifts and each participant completing three conditions of 72 hrs each (Clinicaltrials.gov; registration # NCT04469803). The three conditions tested included no-nap, a 30-min nap opportunity, and a 2-hr nap opportunity. Naps occurred at 02:00 hrs. Cognitive performance was assessed with the Brief 3-min Psychomotor Vigilance Test (PVT-B). Four PVT-B measures include: reaction time (RT in milliseconds (ms)), lapses (RT > 355 ms), false starts (reactions before stimulus or RT <100 ms), and speed (1,000/RT). The PVT-B was performed at the start of the simulated night shift (19:00), end of shift (07:00), pre-nap (02:00), and at 0 mins, 10 mins, 20 mins, and 30 mins following the 30-min and 2-hr nap conditions. Simultaneously, participants reported subjective ratings of fatigue and other constructs. Results Twenty-eight (15 female), mostly certified emergency medical technicians or paramedics, consented to participate. For all three conditions, looking within condition, PVT-B lapse performance at the end of the 12-hr simulated night shift (at 07:00) was poorer compared to shift start (p < 0.05). Performance on PVT-B speed, RT, and false starts were poorer at shift end than shift start for the no-nap and 30-min nap conditions (p < 0.05), but not for the 2-hr nap condition (p > 0.05). Compared to pre-nap measures, performance on the PVT-B assessed at 0 mins post-nap showed significant performance declines for lapses and speed for both the 30-min and 2-hr nap conditions (p < 0.05), but not at 10, 20, or 30 mins post-nap. After waking from the 2-hr on-shift nap opportunity (at 0 mins), participants rated sleepiness, difficulty with concentration, and alertness poorer than pre-nap (p < 0.05). Participants in the 30-min nap condition rated alertness poorer immediately after the nap (at 0 mins) compared to pre-nap (p < 0.05) Conclusions While sleep inertia was detectable immediately following short 30-min and long 2-hr nap opportunities during simulated night shift work, deficits in cognitive performance and subjective ratings quickly dissipated and were not detectable at 10–30 mins post-nap.

Original ArticleDaytime naps improve afternoon power and perceptual measures in elite rugby union athletes - A randomized cross-over trial.

Daytime napping are used by elite athletes in both training and match-day settings. Currently, there are limited interventional studies on the efficacy of napping on physical performance in elite team-sport athletes. Therefore, the objective was to investigate the effect of a daytime nap (<1h) on afternoon performance of peak power, reaction time, subjective wellness, and aerobic performance in professional rugby union athletes. A randomised cross-over design was carried out amongst 15 professional rugby union athletes. Athletes performed nap (NAP) and no nap (CON) conditions on two occasions, separated by one week. Baseline testing of reaction time, subjective wellness, and 6-s peak power test on a cycle ergometer was completed in the morning, followed by 2 x 45-minute training sessions, after which athletes completed the NAP or CON condition at 1200h. Following the nap period, baseline measures were retested in addition to a 30-minute fixed intensity interval cycle and a 4-minute maximal effort cycling test. A significant group x time interaction was determined for 6-s peak power output (+157.6 W, p<0.01, d=1.53), perceived fatigue (-0.2 AU, p=0.01, d=0.37) and muscle soreness (-0.1 AU, p=0.04, d=0.75) in favor of the NAP condition. A significantly lower perceived exertion rating (-1.2 AU, p<0.01, d=1.72) was recorded for the fixed intensity session in favour of NAP. This study highlights that utilizing daytime naps between training sessions on the same day improved afternoon peak power and lower perceptions of fatigue, soreness, and exertion during afternoon training in professional rugby union athletes.

Effect of homeostatic pressure on daytime vigilance performance: Evidence from behaviour and resting-state EEG.

Vigilance is highly sensitive to the time-of-day effect and goes through the daytime trough during the period of the post-noon dip. A midday nap could maintain individuals' vigilance at an optimal level. Thus, homeostatic sleep pressure is one of the main reasons for the post-noon dip in daytime vigilance. The current study focussed on the role of homeostatic sleep pressure in the diurnal variation of vigilance performance with normal circadian rhythms and the corresponding neural basis. With 34 healthy adults, we recorded the resting-state electroencephalogram activities and the following vigilance performance measured by psychomotor vigilance test in the morning, the no-nap mid afternoon, and the nap mid afternoon. The circadian process was controlled by measuring vigilance and resting-state electroencephalogram activities at the same time point in the nap and no-nap conditions. Homeostatic sleep pressure accumulated from morning to mid afternoon induced the declined vigilance performance and a global increase in resting-state delta, theta, alpha, and beta1 bands power, and a local increase in beta2 band power in the central region. Furthermore, the more the spontaneous beta2 power increased, the less vigilance declined from morning to mid afternoon. The current findings suggest that homeostatic sleep pressure increased cortical excitability but decreased cortical communication efficiency from morning to mid afternoon. In addition, the activity of the high beta waves probably reflected the compensatory effort to counteract the negative impact of the low arousal state on the following vigilance task by performing more action preparation in the no-nap afternoon.

Is word learning capacity restored after a daytime nap?

Sleep is thought to be involved in the consolidation of new memories encoded during the day, as proposed by complementary learning systems accounts of memory. Other theories suggest that sleep's role in memory is not restricted to consolidation. The synaptic homeostasis hypothesis proposes that new learning is implemented in the brain through strengthening synaptic connections, a biologically costly process that gradually saturates encoding capacity during wake. During slow-wave sleep, synaptic strength is renormalized, thus restoring memory encoding ability. While the role of sleep in memory consolidation has been extensively documented, few human studies have explored the impact of sleep in restoring encoding ability, and none have looked at learning beyond episodic memory. In this registered report we test the predictions made by the complementary learning systems accounts and the synaptic homeostasis hypothesis regarding adult participants' ability to learn new words, and to integrate these words with existing knowledge. Participants took a polysomnographically-monitored daytime nap or remained awake prior to learning a set of new spoken words. Shortly after learning, and again on the following day, we measured participants' episodic memory for new words. We also assessed the degree to which newly learned words engage in competition with existing words. We predicted that sleep before encoding would result in better episodic memory for the words, and facilitate the overnight integration of new words with existing words. Based on existing literature and theory we further predicted that this restorative function is associated with slow-wave and sleep spindle activity. Our pre-registered analyses did not find a significant benefit of napping prior to encoding on word learning or integration. Exploratory analyses using a more sensitive measure of recall accuracy demonstrated significantly better performance in the nap condition compared to the no-nap condition in the immediate test. At the delayed test there was no longer a significant benefit of the nap. Of note, we found no significant effect of slow-wave activity prior to encoding on episodic memory or integration of newly learned words into the mental lexicon. However, we found that greater levels of Stage 2 sleep spindles were significantly associated with greater improvements in lexical competition from the immediate to the delayed test. Therefore, our results demonstrate some support for theories that implicate sleep spindles in restoring encoding capacity.

Effects of short naps during simulated night shifts on alertness and cognitive performance in young adults.

While short daytime naps have been found to provide alertness and performance benefits without inducing sleep inertia, the effects of a similar napping strategy during nights shifts are largely unknown. This study examined the effects of a 20-min nap (scheduled at 2:00 a.m.) during night shifts among 16 participants (mean [SD] age 22.0[1.08]years) who worked in a simulated night shift from midnight (12:00 a.m.) to morning (ending at 6:00 or 8:00 a.m.). The participants underwent both a 'nap condition' and a 'no-nap condition' by engaging in repeated 10-min tasks (four-choice reaction time tasks and vigilance tasks) and 10-min rest. The results showed that compared to the no-nap condition, sleepiness was significantly lower in the nap condition between 3:20 and 5:20 a.m. (p < 0.05). The nap condition also yielded significantly better performance in the vigilance tasks between 2:40 and 5:40 a.m., except at 4:40 am (p < 0.05). However, no significant difference was found in sleepiness and performance in the vigilance task at 5:40 a.m. or immediately after the nap between the two conditions. The results showed that a 20-min nap at 2:00 a.m. did not induce sleep inertia upon waking. Furthermore, it mitigated sleepiness and sustained work performance for 3 h after the nap. However, the effect of napping was no longer observed near the end of the night shift. Considering risks of falling asleep while driving home from work that may cause a traffic accident, further research should examine ways to mitigate sleepiness after a night shift.

Sleep spindles and slow waves are physiological markers for age-related changes in gray matter in brain regions supporting problem-solving skills.

As we age, the added benefit of sleep for memory consolidation is lost. One of the hallmark age-related changes in sleep is the reduction of sleep spindles and slow waves. Gray matter neurodegeneration is related to both age-related changes in sleep and age-related changes in memory, including memory for problem-solving skills. Here, we investigated whether spindles and slow waves might serve as biological markers for neurodegeneration of gray matter and for the related memory consolidation deficits in older adults. Forty healthy young adults (20-35 yr) and 30 healthy older adults (60-85 yr) were assigned to either nap or wake conditions. Participants were trained on the Tower of Hanoi in the morning, followed by either a 90-min nap opportunity or period of wakefulness, and were retested afterward. We found that age-related changes in sleep spindles and slow waves were differentially related to gray matter intensity in young and older adults in brain regions that support sleep-dependent memory consolidation for problem-solving skills. Specifically, we found that spindles were related to gray matter in neocortical areas (e.g., somatosensory and parietal cortex), and slow waves were related to gray matter in the anterior cingulate, hippocampus, and caudate, all areas known to support problem-solving skills. These results suggest that both sleep spindles and slow waves may serve as biological markers of age-related neurodegeneration of gray matter and the associated reduced benefit of sleep for memory consolidation in older adults.

Influence of naps on sedentary time and physical activity in early childhood.

The objective was to determine if, in preschool-aged children, (1) nap habituality is associated with sedentary time and physical activity (movement behaviors), (2) nap physiology is associated with movement behaviors, and (3) if missing a nap, compared to taking a nap, affects movement behaviors on the same day and subsequent day. A within-subjects (44 children; 4.2 ± 0.6years; 55.6% female), at-home study examined two experimental conditions (one afternoon each of nap- and wake-promotion with order counterbalanced) one week apart. Movement behaviors were derived from wrist-worn actigraphy (12.1 ± 3.1days). Average movement behaviors were calculated from the overall study period with experimental days excluded. Movement behaviors were also extracted for the same day and the subsequent day of the two experimental conditions. Polysomnography was recorded during the nap-promoted condition. Children were classified as non-, intermediate-, or habitual-nappers. Although average movement behaviors were different between nap habituality groups, differences were not significant. There were no associations between movement behaviors and nap sleep stages, and no effects for nap condition or condition by nap habituality on same or next day movement behaviors. Findings do not suggest that naps and movement behaviors are related in children. Although a single missed nap was not detrimental to same or next day movement behaviors, future studies should explore effects of multiple days of subsequent nap restriction to examine potential cumulative effects.

Sleep affects higher-level categorization of speech sounds, but not frequency encoding

Sleep can increase consolidation of new knowledge and skills. It is less clear whether sleep plays a role in other aspects of experience-dependent neuroplasticity, which underlie important human capabilities such as spoken language processing. Theories of sensory learning differ in their predictions; some imply rapid learning at early sensory levels, while other propose a slow, progressive timecourse such that higher-level categorical representations guide immediate, novice learning, while lower-level sensory changes do not emerge until later stages. In this study, we investigated the role of sleep across both behavioural and physiological indices of auditory neuroplasticity. Forty healthy young human adults (23 female) who did not speak a tonal language participated in the study. They learned to categorize non-native Mandarin lexical tones using a sound-to-category training paradigm, and were then randomly assigned to a Nap or Wake condition. Polysomnographic data were recorded to quantify sleep during a 3 h afternoon nap opportunity, or equivalent period of quiet wakeful activity. Measures of behavioural performance accuracy revealed a significant improvement in learning the sound-to-category training paradigm between Nap and Wake groups. Conversely, a neural index of fine sound encoding fidelity of speech sounds known as the frequency-following response (FFR) suggested no change due to sleep, and a null model was supported, using Bayesian statistics. Together, these results support theories that propose a slow, progressive and hierarchical timecourse for sensory learning. Sleep's effect may play the biggest role in the higher-level learning, although contributions to more protracted processes of plasticity that exceed the study duration cannot be ruled out.

Physiological response and physical performance after 40 min and 90 min daytime nap opportunities

ABSTRACT This study aimed to examine the impact of 40-min and 90-min naps on performance in the 5-m shuttle run test (5mSRT) and on various physiological and perceptual measures. Sixteen male athletes (20 ± 3 years, 173 ± 7 cm, 67 ± 7 kg) performed the 5mSRT after a 40-min nap (N40), after a 90-min nap (N90), and in a no-nap, control condition (N0). The 5mSRT involves six repetitions of 30 s of all-out exercise. Total distance (in the six repetitions) and highest distance (in a single repetition) in the 5mSRT were greater after naps than in N0 (p < 0.001), and the total distance, which reflects the anaerobic capacity, was greater in N90 than in N40 (p < 0.05). Physiological and perceptual responses were favourable in both nap conditions (p < 0.01), more so in N90 than in N40 (p < 0.05). Together, the results support the contention that physiological/perceptual responses after napping contribute to improved exercise performance and that longer naps are more effective.

0092 The Effects of Slow-Oscillatory Galvanic Vestibular Stimulation on Sleep Physiology in Healthy Humans

Abstract Introduction Recent studies have demonstrated that rocking promotes sleep in animals and humans. The application of an alternating current galvanic vestibular stimulation (GVS) can elicit body sway like rocking sensation. Here, we examined the effects of slow-oscillatory GVS, which can evoke the virtual rocking sensation in the brain, on objective and subjective sleep quality in healthy young adults. Methods We studied 14 healthy subjects (age: 22.7 p/m 1.4 years) who underwent 3 nap conditions (adaptation, sham [SHAM], and stimulation [STIM]), where SHAM and STIM were randomly allocated with a 1-week interval in general. The polysomnographic recordings were started at 2 pm and time in bed was restricted to 90 min for all subjects. In both conditions, electrodes were placed on both mastoids for GVS; in STIM condition, the slow-oscillatory (0.25 Hz sinusoidal) GVS was applied throughout the nap period with a current intensity of approximately 80% of sensory thresholds of each subject. The pattern of center of pressure during quiet standing was also measured using a force plate, with or without the same slow-oscillatory GVS. We analyzed sleep variables and electroencephalographic (EEG) spectral power and compared them between STIM and SHAM. Subjective sleep quality was also measured and compared between STIM and SHAM. Results We confirmed that subsensory slow-oscillatory GVS induced body sway corresponding to the stimulation frequency for all subjects. We found that sleep latency was significantly shorter and total sleep time as well as N2 duration were significantly longer in STIM than in SHAM. N3 duration did not differ significantly between the conditions. EEG power spectrum densities in delta, theta, and sigma bands were significantly greater in STIM than in SHAM. Subjective sleep quality was significantly better in STIM than in SHAM. Conclusion We demonstrated that subsensory slow-oscillatory GVS facilitated wake-sleep transition and improved objective and subjective sleep quality. The results suggest that weak periodic inputs into vestibular systems promote sleep by modulating the thalamocortical mechanisms in humans. This finding may open a new avenue toward a development of novel techniques for human sleep augmentation. Support (If Any) JST PRESTO (JPMJPR19J3) and JSPS KAKENHI (18K17891) to AK.

0150 Afternoon Napping Does Not Impact Autonomic Function in Healthy Adults

Abstract Introduction Proper overnight sleep is important for autonomic nervous system function. However, less is known about the effects of daytime napping on wake autonomic regulation. In the present study, we assessed autonomic function following a daytime nap. We hypothesized that a 90-minute afternoon nap would significantly improve wake heart rate variability (HRV) and blood pressure (BP). Methods Fourteen participants (7 female, 24±1 years, 24 ±1 kg/m2) took part in the study. Subjects completed an autonomic function test after no nap (control condition) or a 90-minute nap opportunity (nap condition) on separate days using a randomized, crossover design. During the autonomic test, participants were fitted with three-lead electrocardiography (ECG), continuous beat-to-beat blood pressure (Finapres NOVA, Netherlands), and respiratory monitoring (pneumobelt). The autonomic function test consisted of 5-minutes of spontaneous breathing, 5-minutes of controlled breathing (15 breaths/min), and a 2-minute cold pressor test (CPT). Frequency-domain HRV in the low (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components were determined via Fast Fourier transformation. Time-domain HRV was quantified using RMSSD and pNN50. Paired sample t-tests were completed between the control and nap sessions. Results Mean total sleep time (TST) for the nap session was 74±5 minutes. Contrary to our hypothesis, an afternoon nap did not change wake heart rate (HR, Control: 70±3 vs. Nap: 68±3 bpm, p = .31) or mean arterial pressure (MAP, Control: 77±3 vs. Nap: 83±3 mmHg, p = 0.70). Similarly, no differences were observed in HF (Control: 2632±628 vs. Nap: 2150±494 ms2, p = .33), LF (Control: 1702±373 vs. Nap: 1345±257 ms2, p = .20), or LF/HF (Control: 92±16 vs. Nap: 92±17%, p = .97) between conditions. RMSSD (Control: 82±12 vs. Nap: 79±11 ms, p = .723) and pNN50 (Control: 43±6 vs. Nap: 47±6%, p = .30) were not impacted by a daytime nap. Lastly, changes in HR (Control: ∆14±3 vs Nap: ∆18±3 bpm, p = .114) and MAP (Control: ∆23±4 vs. ∆Nap: 27±4 mmHg, p = .28) during CPT were not different between conditions. Conclusion An afternoon nap does not appear to significantly influence autonomic function at rest or during CPT in young healthy adults. Support (If Any)

0110 Nap-Related Change in Memory Precision may be Related to Slow-Wave Sleep in Early Childhood

Abstract Introduction In early childhood (3-5 years), naps comprise part of children’s 24-hr sleep. Naps support some types of learning (declarative, emotional), enhancing children’s ability to correctly identify previously seen items. During this time, children’s ability to form precise memories also improves, likely due to ongoing hippocampal development and maturation of processes allowing for pattern separation. Whether naps support the ability to form precise memory representations, allowing children to discriminate between previously seen vs. similar but novel items, is unclear. Here, we used a mnemonic similarity task to examine whether daytime naps support children’s recall of specific images more so than a period of wake. Further, we tested whether this nap-related improvement persists across overnight sleep. We hypothesized that task improvement would be associated with slow-wave sleep (SWS), as this stage has been shown to support episodic memory in preschool-aged children. Methods Participants (N=7, 4 females, Mage=56.1 mos) encoded items in the morning, verbally categorizing each image as something they would find “inside” or “outside”. They recalled items at three time points: immediately following encoding, after their nap/wake period, and the following morning after overnight sleep. Recall involved being shown a single image and responding whether it had been previously seen or not. Recall items included targets, foils, and lures. PSG was recorded during the nap and overnight sleep bouts. Results When controlling for age, children forgot fewer target items following a nap than a comparable period of wake (p=.05). Following a nap and overnight sleep, children also exhibited marginally less forgetting of target items than following a period of wake and overnight sleep (p=.102). Lure discrimination index (LDI; false alarm lures minus false alarm foils) did not differ between nap and wake conditions. Change in target recall following the nap was associated with SWS% during the nap (r=.96, p=.01), but not nap duration (p=.27). Conclusion Napping supported children’s ability to recall target items, but not to correctly reject lures, suggesting naps’ benefit towards more generalized memory. Nap SWS% was associated with less forgetting of target items, supporting its role in hippocampal-dependent memory consolidation. Analyses of overnight sleep data and inclusion of more participants may help better elucidate the relationship between preschool children’s sleep and memory development. Support (If Any) NSF BCS 1749280 NIH R21 HD094758 NIH R01 HL111695