In the QW group (n = 21), subjects were attached to electroencephalographic electrodes and watched a nature videotape lasting 50 min while lying in bed. For the Novel condition, sleep variables did not significantly predict performance in model 1 [F(3,13) = 0.89, P = 0.47]. Lines denote bidirectional connections, and arrows denote monodirectional projections. The answer to this example problem is SWEET (e.g., cookies are sweet, sweet sixteen, sweetheart). Each RAT problem contains a triplet of words presented horizontally along with a blank space. To retain more statistical power, future studies should explore these relationships in a nocturnal sleep paradigm. After adding the HRV variables in model 2, this model was still not significant [F(5,11) = 1.86, P = 0.18; Fig. Alcohol is a central nervous system depressant that causes brain activity to slow down. The brainstem connects with the thalamus, hypothalamus, and other memory-related areas, including the hippocampus, amygdala, and PFC. One possible influence that has received little attention in the sleep and memory literature is the autonomic nervous system (ANS). However, model 2 suggests HF HRV may be an even better predictor of explicit memory improvement, implicating previously unidentified avenues of research into how autonomic fluctuations interact with known markers of sleep-dependent plasticity. 3], with REM minutes (β = −0.55, P = 0.01) and sleep spindles (β = 0.51, P = 0.02) emerging as significant predictors, whereas time spent in SWS was not a significant predictor (β = −0.06, P = 0.77; Table S4). “The dilated blood vessels and increased blood flow may help the brain move waste products out of the brain,” he said. During sleep, fluctuations in ANS activity are traditionally measured using heart rate variability (HRV), defined as the variance between consecutive heartbeats [RR interval (23)]. This method emphasizes consolidated sleep stages and resulted in different percentages of ECG epochs for the HRV analysis. Interestingly, we noted that compared with baseline performance, the QW group showed a decrease in performance in the Primed condition [t(20) = −2.63, P = 0.02], an increase in performance in the Repeated condition [t(20) = 2.06, P = 0.05], and no difference in the Novel condition [t(20) = −0.09, P = 0.93]. Pearson correlation coefficients (Bonferroni-corrected) were used to examine the bivariate relationship between HF HRV during sleep, minutes in each sleep stage, sleep spindles, and all performance conditions. NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. Interplay between spontaneous and induced brain activity during human non-rapid eye movement sleep. Specifically, during REM sleep, the PFC shows increased neural activity compared with other sleep stages (65). After accounting for ANS activity, sleep spindles decreased in significance (β = 0.32, P = 0.063). Many people like watching TV to relax after a long workday, and while that might help distract you from your daily worries, it doesn’t prepare your brain for a good night’s rest. This period of high plasticity and low sensory input (sleep) may situate REM sleep as a brain state optimized for making connections between disparate ideas, which is a principal definition of creativity (32). On average, a 90-min nap will typically comprise about 15–20 min of REM sleep (5, 48, 49). 2). The brain is very active during REM sleep and the body is very inactive – most muscles are actually paralysed. Amanda Rodewald, Ivan Rudik, and Catherine Kling talk about the hazards of ozone pollution to birds. Ten problems were exactly the same as the AM baseline RAT problems (Repeated condition), 10 problems had the same answers as 10 (out of 30) of the AM analogies (Primed condition), and 10 problems were completely novel (Novel condition). However, only the group with REM sleep improved in the Primed condition. For 11 nap subjects, we were unable to detect an RR interval and were unable to perform HRV analyses for these subjects, so they were excluded. It is thought that excessive EMG activity in RBD reflects dysfunction of the brainstem structures responsible for muscle atonia during REM sleep.1In animals, experimental lesions in the brainstem produce increased tonic and phasic EMG activity and abnormal behaviors during REM sleep.2–5In humans, RBD can be idiopathic or associated with neurodegenerative diseases.6Follow … As such, we were unable to examine the added benefit of REM sleep directly and reliably above and beyond NREM sleep only. Epochs of stage 1 and wake after sleep onset were not analyzed, because these periods have not been previously reported to contribute to memory consolidation. Participants had a regular sleep-wake schedule (reporting a habitual time in bed of 7–9 h per night as assessed by actigraphy), and no presence or history of sleep, psychiatric, cardiovascular, or neurological disorder determined during an in-person, online, or telephone interview. In contrast, decreased resting HF HRV is associated with poor cognitive function and maladaptive emotional processing (14, 26). Although SWS was not a significant predictor of performance, sleep spindles contributed to performance benefits in model 1 in both Primed and Repeated conditions, and this result extends previous research implicating sleep spindles in explicit verbal memory consolidation (3, 46) and suggests a role for spindles in predicting implicit memory performance (47) as well. Using a regression framework, we examined the amount of performance change (computed as proportion correct PM − proportion correct AM/proportion correct AM * 100; Table 2 and SI Materials and Methods) in each condition accounted for by the sleep predictors in model 1, as well as the sleep and HRV predictors in model 2. Using functional magnetic resonance imaging, Lane et al. For both the Primed and Repeated conditions, model 2 (sleep + HRV) predicted performance significantly better (73% and 58% of variance explained, respectively) compared with model 1 (sleep only, 46% and 26% of variance explained, respectively). This analysis revealed a significant effect of group [F(3,51) = 6.57, P = 0.001, ηp2= 0.28]. Additionally, we varied which set of 10 problems in each group of 30 would be assigned to Novel, Repeated, and Primed conditions. REM is a deep stage of sleep with intense brain activity in the forebrain and midbrain. For individuals with REM sleep behavior disorder, paralysis does not occur during the REM stage. This session ended at 3:30 PM, and subjects were allowed to leave the laboratory. In addition, REM sleep shows both greater total ANS activity and higher parasympathetic/vagal activity compared with wake and SWS sleep (25). Image credit: Acacia Dishman/Medical College of Wisconsin. Due to the restrictions of HRV calculations (SI Materials and Methods), we could only conduct regressions on a subset of subjects (17 nappers). This process can be particularly helpful for storing information related to motor tasks, like driving, swinging a tennis racquet or practicing a new dance move, so that these tasks become automatic. It is therefore possible that two parallel mechanisms may facilitate performance improvement in the explicit memory condition, one during a quiet wake episode involving rehearsal or rumination on the RAT items, and the other involving memory reactivation processes during sleep. Also, vagal stimulation has been shown to boost neural representations of paired movements in the motor cortex (19) and to enhance extinction learning of fear memories (20). The neuromodulator profile of REM sleep reveals a powerful boost in acetylcholine, combined with a diminished role of norepinephrine and serotonin (55). Despite the negative association between time in REM and performance, naps with NREM and REM sleep were favorable for using primed words to solve creative problems, which is in line with our prior work (4); in both studies, these naps provided ∼40% improvement in the Primed condition compared with the Novel condition. Other neurotransmitters that shape sleep and wakefulness include acetylcholine, histamine, adrenaline, cortisol, and serotonin. (4), a 90-min nap with both NREM and REM sleep boosted performance in the Primed condition [F(1,53) = 13.63, P = 0.001, ηp2 = 0.20] above QW. We present the first evidence, to our knowledge, that the autonomic nervous system (ANS) plays a role in associative memory consolidation during sleep. Another drawback of the current study is the lack of NREM-only naps available for analysis (n = 8). Peripheral activity has been purported to affect memory consolidation via vagal afferent nerve fibers, which communicate information about ANS excitation and arousal via projections to the brainstem, which then project to memory-related areas, including the amygdala complex, hippocampus, and prefrontal cortex (PFC) (11). Error bars represent ±1 SEM. Multiple linear regression analyses were used to develop models that could predict performance change on each RAT condition from sleep parameters and HF HRV during sleep. Sleep-deprived EEG tests One of the most common EEG tests is sleep-deprived EEG conducted by neurologists to recognize any abnormal brain wave activity and sleep disorders. No improvement was seen the Nap group in the Novel or Repeated condition compared with QW, although in the Repeated condition, the Nap group nominally performed better than the QW group. We specifically examined sleep features previously associated with memory consolidation, including minutes in REM, minutes in SWS, and sleep spindles. At 5:00 PM, subjects returned to the laboratory and were tested on 30 RAT problems with a time limit of 40 min. Excessive sleepiness is the feeling of being especially tired or drowsy during the day. Reduced sleep spindles and spindle coherence in schizophrenia: Mechanisms of impaired memory consolidation? Throughout history, psychologists and philosophers have proposed that good sleep benefits memory, yet current studies focusing on the relationship between traditionally reported sleep features (e.g., minutes in sleep stages) and changes in memory performance show contradictory findings. (C) In the Repeated condition, sleep alone predicted a portion of performance change (model 1: Adj R2 = 0.26, P = 0.07), whereas sleep + HF HRV significantly increased the amount of variance accounted for in performance change (model 2: Adjusted R2 = 0.58, P = 0.009). Note that these results are in line with previous research (4). Because previous data have indicated that REM sleep was important for this task, we further parsed the data into those subjects who received both NREM and REM sleep (n = 35) and those subjects who did not (n = 13). It is also important to note that the regression analyses revealed that REM sleep accounted for a greater amount of variance compared with all other sleep features. Using regression analyses, we compared the proportion of variance in performance associated with traditionally reported sleep features (model 1) vs. sleep features and HRV during sleep (model 2). REM sleep showed the highest total power, which was significantly greater than SWS (P < 0.001). This article is a PNAS Direct Submission. performed research; L.N.W., N.C., K.A.D., and S.C.M. Neither the Repeated condition [F(1,35) = 0.04, P = 0.84, ηp2= 0.001] nor the Novel condition [F(1,35) = 0.79, P = 0.38, ηp2= 0.02] differed for nappers and QW. In the current study, REM sleep may have facilitated subjects’ ability to break the schematic relationship between words presented as analogies and enhanced their ability to use the analogy answers in a new and useful way to complete the unrelated RAT problems. Because naps have more fragmented sleep due to increased stage transitions, the traditional method of HRV analysis decreased the number of subjects that could be analyzed. It occurs cyclically several times during sleep, … The RAT measures creative processing and is associated with PFC activity (33). 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