Slow wave sleep during a daytime nap is necessary for protection from subsequent interference and long-term retention

While it is now generally accepted that sleep facilitates the processing of newly acquired declarative information, questions still remain as to the type and length of sleep necessary to best benefit declarative memories. A better understanding could lend support in one direction or another as to the much-debated role of sleep, be it passive, permissive, or active, in memory processing. The present study employed a napping paradigm and compared performance on a bimodal paired-associates task of those who obtained a 10-min nap, containing only Stages 1 and 2 sleep, to those whose nap contained slow-wave sleep (SWS) and rapid eye movement (REM) sleep (60-min nap), as well as to subjects who remained awake. Measurements were obtained for baseline performance at training, after a sleep/no sleep interval for short-term retention, after a subsequent stimulus-related interference task, and again after a weeklong retention period. While all groups learned the information similarly, both nap groups performed better than the Wake group when examining short-term retention, approximately 1.5h after training (10-min p=.052, 60-min p=.002). However, performance benefits seen in the 10-min nap group proved to be temporary. Performance after a stimulus-related interference task revealed significantly better memory retention in the 60-min nap group, with interference disrupting the memory trace far less than both the Wake and 10-min nap groups (p<.001, p=.006, respectively). After a weeklong retention period, sleep's benefit to memory persisted in the 60-min nap group, with performance significantly greater than both the Wake and 10-min nap groups (p<.001, p=.004, respectively). It is our conclusion that SWS, obtained only by those in the 60-min nap group, served to actively facilitate the consolidation of learned bimodal paired-associates, supported by theories such as the Standard Theory of Consolidation as well as the Synaptic Homeostasis Hypothesis.     

The road not taken: creative solutions require avoidance of high-frequency responses

To investigate individual differences in creativity as measured with a complex problem-solving task, we developed a computational model of the remote associates test (RAT). For 50 years, the RAT has been used to measure creativity. Each RAT question presents three cue words that are linked by a fourth word, which is the correct answer. We hypothesized that individuals perform poorly on the RAT when they are biased to consider high-frequency candidate answers. To assess this hypothesis, we tested individuals with 48 RAT questions and required speeded responding to encourage guessing. Results supported our hypothesis. We generated a norm-based model of the RAT using a high-dimensional semantic space, and this model accurately identified correct answers. A frequency-biased model that included different levels of bias for high-frequency candidate answers explained variance for both correct and incorrect responses. Providing new insight into the nature of creativity, the model explains why some RAT questions are more difficult than others, and why some people perform better than others on the RAT.     

The differential effects of emotional salience on direct associative and relational memory during a nap

Relational memories are formed from shared components between directly learned memory associations, flexibly linking learned information to better inform future judgments. Sleep has been found to facilitate both direct associative and relational memories. However, the impact of incorporating emotionally salient information into learned material and the interaction of emotional salience and sleep in facilitating both types of memory is unknown. Participants encoded two sets of picture pairs, with either emotionally negative or neutral objects paired with neutral faces. The same objects were present in both sets, paired with two different faces across the sets. Baseline memory for these directly paired associates was tested immediately after encoding, followed by either a 90-min nap opportunity or wakefulness. Five hours after learning, a surprise test assessed relational memory, the indirect association between two faces paired with the same object during encoding, followed by a retest of direct associative memory. Overall, negative information was remembered better than neutral for directly learned pairs. A nap facilitated both preservation of direct associative memories and formation of relational memories, compared to remaining awake. Interestingly, however, this sleep benefit was observed specifically for neutral directly paired associates, while both neutral and negative relational associations benefitted from a nap. Finally, REM sleep played opposing roles in neutral direct and relational associative memory formation, with more REM sleep leading to forgetting of direct associations but promoting relational associations, suggesting that, while not benefitting memory consolidation for directly learned details, REM sleep may foster the memory reorganization needed for relational memory.     

A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory

The specialized role that sleep-specific brain physiology plays in memory processing is being rapidly clarified with a greater understanding of the dynamic, complex, and exquisitely orchestrated brain state that emerges during sleep. Behaviorally, the facilitative role of non-REM (NREM) sleep (primarily slow wave sleep) for declarative but not procedural memory performance in humans has been demonstrated in a number of nocturnal sleep studies. However, subjects in these studies were tested after periods of sleep that contained REM sleep in addition to NREM sleep, and comparison wake groups were subjected to mild sleep deprivation. To add some clarity to the findings of these nocturnal studies, we assessed performance on declarative and procedural memory tasks following a daytime training-retest interval containing either a short nap that included NREM without REM sleep, or wakefulness. Consistent with previous findings we show that, after a comparatively brief sleep episode, subjects that take a nap improve more on a declarative memory task than subjects that stay awake, but that improvement on a procedural memory task is the same regardless of whether subjects take a nap or remain awake. Slow wave sleep was the only sleep parameter to correlate positively with declarative memory improvement. These findings are discussed with reference to the general benefits of napping and within the broader context of a growing literature suggesting a role for NREM-specific physiology for the processing of declarative memory.     

The Role of an Incubation Period in Creative Problem Solving

ABSTRACT

This experimental study tested the spreading-activation hypothesis that an incubation period helps to sensitize problem solvers to relevant concepts. The study also tested the selective forgetting hypothesis that an incubation period helps to desensitize problem solvers to irrelevant concepts. Chinese Chess GO players, 28 experts and 29 novices, solved 18 remote association tasks (RAT) and lexical decision tasks (LDTs) under immediate, rest, and incubation conditions. After each RAT, a set of LDTs incorporating the RAT solution and the irrelevant concept were presented, either immediately, or after a 2-min delay, or after a 2-min delay filled with incubation tasks. The findings of the study support the spreading activation hypothesis and suggest that spreading activation occurs only in a fixated mind. No support was found for the selective forgetting hypothesis.     

‘No Man is an Island’: Effects of social seclusion on social dream content and REM sleep

Based on the Social Simulation Theory of dreaming (SST), we studied the effects of voluntary social seclusion on dream content and sleep structure. Specifically, we studied the Compensation Hypothesis, which predicts social dream contents to increase during social seclusion, the Sociality Bias – a ratio between dream and wake interactions – and the Strengthening Hypothesis, which predicts an increase in familiar dream characters during seclusion. Additionally, we assessed changes in the proportion of REM sleep. Sleep data and dream reports from 18 participants were collected preceding (n = 94), during (n = 90) and after (n = 119) a seclusion retreat. Data were analysed using linear mixed-effects models. We failed to support the Compensation Hypothesis, with dreams evidencing fewer social interactions during seclusion. The Strengthening Hypothesis was supported, with more familiar characters present in seclusion dreams. Dream social interactions maintained the Sociality Bias even under seclusion. Additionally, REM sleep increased during seclusion, coinciding with previous literature and tentatively supporting the proposed attachment function for social REM sleep.     

REM sleep and the analytic process: a psychophysiologic bridge.

Recent research on the physiology of REM sleep has supported the hypothesis that it serves processes of psychologic adaptation. This study examines the relationship between physiologic parameters of REM sleep and evidence in analytic material of the need for adaptation. Significant correlations were found between defensive strain before sleep and REM latency, and between change in defensive strain from evening to morning and total REM time.     

The effect of subliminal priming on sleep duration

Two experiments primed college students with either sleep‐related or neutral words and then assessed sleep during a 25 minute nap period. Both experiments showed that participants primed with sleep‐related words reported having slept longer than did those primed with neutral words. Furthermore, both experiments showed that sleep‐primed participants exhibited lower heart rate. Experiment 2 also revealed that the effect of the priming manipulation was especially strong among participants who had trouble sleeping. This suggests that priming might be a cost‐effective treatment for inducing sleep among people with sleep problems.     

Differential responding to the beta movement after waking from REM and nonREM sleep.

Ten young adults were wakened from REM sleep and from nonREM sleep on two nonconsecutive nights and were tested to determine their upper and lower beta-movement thresholds. The ranges of the illusion were found to be significantly wider after waking from REM sleep than after waking from nonREM sleep or before sleep. The differential responding to the beta movement supports the experimental hypothesis that apparent motion may provide sensitive detectors of the operation during wakefulness of the Basic Rest-Activity Cycle, of which REM and nonREM sleep are opposite phases that carry over into wakefulness.     

On dreaming at sleep onset.

The position that dreaming occurs exclusively during REM sleep, which has its first onset after sixty to ninety minutes of nonREM sleep, has been effectively refuted in sleep laboratories but remains uncorrected in the psychoanalytic literature. Examples of hallucinatory activity occurring during the sleep onset period and during a brief nap are shown to have all the characteristics of dreams, including latent content related to repressed material from childhood.     

Effects of a limited nap on night sleep in older subjects

The night sleep of sixteen 50-60-year-old women, which had been preceded by either afternoon naps or no-nap control periods, was assessed by polygraphic and subjective measures. There were 2 nap and 2 non-nap nights. The naps were limited to a 1-hr opportunity. The measures of all subjects, good nappers (more than 20-min sleep on both nap occasions), and subjects with 50-min or more nap time, were separately analyzed. The null hypothesis of a nap effect could not be rejected. Within limits, naps may be recommended to offset the common night-time awakenings in older persons.     

Zen meditation and access to information in the unconscious

In two experiments and two different research paradigms, we tested the hypothesis that Zen meditation increases access to accessible but unconscious information. Zen practitioners who meditated in the lab performed better on the Remote Associate Test (RAT; Mednick, 1962) than Zen practitioners who did not meditate. In a new, second task, it was observed that Zen practitioners who meditated used subliminally primed words more than Zen practitioners who did not meditate. Practical and theoretical implications are discussed.     

REM need in adolescents as indicated by resistance to REM deprivation.

The hypothesis that adolescents have an exceptionally strong need for REM sleep was tested by measuring their resistance to REM deprivation. Ten adolescents (aged 16 to 17 yr.) were compared with 12 young adults (aged 25 to 27 yr.) in a standard REM deprivation procedure. The adolescents had to be awakened significantly more times than the young adults; this is consistent with the hypothesis that adolescents have a greater need for REM sleep.     

Spiral aftereffect durations following awakening from REM sleep and non-REM sleep

Nine Ss were awakened 2 min after the beginning of a REM period and 2 min after the beginning of a non-REM period (Stage 4), and were tested on a spiral aftereffect. The duration of the spiral aftereffect was found to be longer for the tests made following REM periods than for the tests made following non-REM periods. The results were interpreted to suggest a possible “carry over” effect from the particular sleep, stage into the waking state.     

Autonomy and control in dyads: effects on interaction quality and joint creative performance

Two studies examined interaction quality and joint performance on two creative tasks in unacquainted dyads primed for autonomy or control orientations. It was hypothesized that autonomy-primed dyads would interact more constructively, experience more positive mood, and engage the task more readily, and as a result these dyads would perform better. To test this, Study 1 primed orientation and explored verbal creative performance on the Remote Associates Task (RAT). In Study 2, dyads were primed with autonomy and control orientation and videotaped during two joint creative tasks, one verbal (RAT) and one nonverbal (charades). Videotapes were coded for behavioral indicators of closeness and task engagement. Results showed that autonomy-primed dyads felt closer, were more emotionally and cognitively attuned, provided empathy and encouragement to partners, and performed more effectively. The effects of primed autonomy on creative performance were mediated by interpersonal quality, mood, and joint engagement.     

Daytime naps improve motor imagery learning

Sleep is known to contribute to motor memory consolidation. Recent studies have provided evidence that a night of sleep plays a similar functional role following motor imagery (MI), while the simple passage of time does not result in performance gains. Here, we examined the benefits of a daytime nap on motor memory consolidation after MI practice. Participants were trained by MI on an explicitly known sequence of finger movements at 11:00. Half of the participants were then subjected (at 14:00) to either a short nap (10 min of stage 2 sleep) or a long nap (60–90 min, including slow wave sleep and rapid eye movement sleep). We also collected data from both quiet and active rest control groups. All participants remained in the lab until being retested at 16:00. The data revealed that a daytime nap after imagery practice improved motor performance and, therefore, facilitated motor memory consolidation, as compared with spending a similar time interval in the wake state. Interestingly, the results revealed that both short and long naps resulted in similar delayed performance gains. The data might also suggest that the presence of slow wave and rapid eye movement sleep does not provide additional benefits for the sleep-dependent motor skill consolidation following MI practice.     

无意识加工对创造性问题解决的促进效应

以远距离联想测验(RAT)和字谜作为实验材料,采用改进的掩蔽启动实验范式,探讨无意识加工对创造性问题解决的影响。结果发现:(1)无论是完成远距离联想任务还是字谜任务,被试在启动和无启动条件下的正确率均无显著差异;(2)在两类任务下,对于高难度的创造性问题,启动条件下的正确率显著高于无启动条件。对于低难度的创造性问题,启动条件下RAT的正确率显著低于无启动条件,字谜的正确率在两种条件下无显著差异;(3)随着创造性问题难度降低,无意识信息的促进效应逐渐减小,对于低难度的创造性问题,无意识信息反而会起到抑制作用。这表明,无意识加工对随后的创造性问题解决过程具有促进效应,而且这种效应只有在解决高难度的创造性问题时才会体现。     

Self-awakening, sleep inertia, and P3 amplitude in elderly people

It is well known that sleepiness is sometimes experienced in the afternoon. A short afternoon nap is thought to be effective in reducing sleepiness. However, sleep inertia occurs even after a short nap, and this could be a major risk factor for injuries from falling by the elderly. In the present study, the effect of self-awakening on sleep inertia after a 20-min. nap was examined. Nine participants (M=74.1 yr., SD=5.0 yr.) took part in the three experimental conditions: the self-awakened nap, the forced-awakened nap, and the control (no-nap) conditon. Analysis showed sleepiness and performance after the nap significantly improved compared with the control condition. P3 amplitude tended to be larger after self-awakening than after forced-awakening. The present study indicates a 20-min. nap reduces afternoon sleepiness, and the application of self-awakening may contribute to higher arousal after a nap taken by this elderly group.     

Daydreams and nap dreams: Content comparisons

Differences between nighttime REM and NREM dreams are well-established but only rarely are daytime REM and NREM nap dreams compared with each other or with daydreams. Fifty-one participants took daytime naps (with REM or NREM awakenings) and provided both waking daydream and nap dream reports. They also provided ratings of their bizarreness, sensory experience, and emotion intensity. Recall rates for REM (96%) and NREM (89%) naps were elevated compared to typical recall rates for nighttime dreams (80% and 43% respectively), suggesting an enhanced circadian influence. All attribute ratings were higher for REM than for NREM dreams, replicating findings for nighttime dreams. Compared with daydreams, NREM dreams had lower ratings for emotional intensity and sensory experience while REM dreams had higher ratings for bizarreness and sensory experience. Results support using daytime naps in dream research and suggest that there occurs selective enhancement and inhibition of specific dream attributes by REM, NREM and waking state mechanisms.     

Assessment of Personality Organization in Couple Relationships: Factorial Structure of the Inventory of Personality Organization and Incremental Validity Over Neuroticism

Summary: Creative thinking was explored from several approaches to further understanding of the interrelationship of perception, personality, and cognition. College students (N = 45) were administered the Group Embedded Figures Test (GEFT), the Remote Associates Test (RAT), a questionnaire concerning RAT strategy, and two self-report scales. Field independent subjects were found to be significantly (p < .001) more creative than field dependents. Correlations between the RAT and GEFT and the self-report measures of conformity and creativity, while largely nonsignificant, were in the predicted directions. Results demonstrated that advanced strategy levels and insightful responses were significantly related to high performance on the RAT. Theoretical links between cognitive style and Piagetian concepts were discussed in regard to creative thought. Overall, these findings support the contention that the creative processes should be studied, not as isolated structures, but with relational and multifaceted emphasis.