I know how you felt last night,or do I? Self- and external ratings of emotions in REM sleep dreams

We investigated whether inconsistencies in previous studies regarding emotional experiences in dreams derive from whether dream emotions are self-rated or externally evaluated. Seventeen subjects were monitored with polysomnography in the sleep laboratory and awakened from every rapid eye movement (REM) sleep stage 5 min after the onset of the stage. Upon awakening, participants gave an oral dream report and rated their dream emotions using the modified Differential Emotions Scale, whereas external judges rated the participants’ emotions expressed in the dream reports, using the same scale. The two approaches produced diverging results. Self-ratings, as compared to external ratings, resulted in greater estimates of (a) emotional dreams; (b) positively valenced dreams; (c) positive and negative emotions per dream; and (d) various discrete emotions represented in dreams. The results suggest that this is mostly due to the underrepresentation of positive emotions in dream reports. Possible reasons for this discrepancy are discussed.     

Cognitive asymmetry and dreaming: lack of relationship

The present study investigated the relationship between cognitive laterality and dream recall, dream characteristics, and eye movement density in rapid eye movement (REM) sleep. Fifty-two right-handed males, age 20-30 years, were tested on a six-test battery of which three tests measure right hemisphere function and three tests measure left hemisphere function. Based on their performance, 14 subjects were selected for a sleep laboratory study. Each spent 3 experimental nights in the laboratory during which they were awakened from REM sleep for dream reports. Dream reports were scored for bizarreness, emotions, visual elements, and overall "dreamlike" versus "thoughtlike" character. Subjects were awakened from 123 REM periods, of which 96 yielded positive dream reports (78.04%). Neither the rate of recall nor the four evaluation scores were correlated with the laterality scores that were constructed from the six-test battery. Eye movement density during REM sleep was significantly positively correlated with the total performance of the two hemispheres. These results do not support the alleged lateralization of dreaming. In agreement with recent reports in the literature, it is concluded that dreaming cannot be seen as a "right hemisphere" function.     

Cognitive aspects of mental activity during sleep.

Upon nighttime experimental awakening of 27 subjects in four sleep conditions (sleep onset early; sleep onset late; Stage 2; and rapid eye movement, REM, sleep), 108 dream reports and their association reports were collected. Dream reports were analyzed for length (temporal units) and content categories (continuity; implausibility; presence of the dreamer [i.e., "the self"], a setting, characters). Associations were classified as episodic, abstract self-referred, and semantic memories. The two sets of results tend to show a basic homogeneity among mentation reports in the four sleep conditions considered. These findings are interpreted as supporting the hypothesis that the same cognitive mechanisms operate, at different levels of engagement, in dream generation rather than the hypothesis of multiple dream-generation systems dependent upon the physiological characteristics of the various sleep stages.     

Normal body scheme and absent phantom limb experience in amputees while dreaming

While dreaming amputees often experience a normal body image and the phantom limb may not be present. However, dreaming experiences in amputees have mainly been collected by questionnaires. We analysed the dream reports of amputated patients with phantom limb collected after awakening from REM sleep during overnight videopolysomnography (VPSG). Six amputated patients underwent overnight VPSG study. Patients were awakened during REM sleep and asked to report their dreams. Three patients were able to deliver an account of a dream. In all dreaming recalls, patients reported that the amputated limbs were intact and completely functional and they no longer experienced phantom limb sensations. Phantom limb experiences, that during wake result from a conflict between a pre-existing body scheme and the sensory information on the missing limb, were suppressed during sleep in our patients in favour of the image of an intact body accessed during dream.     

The ability to self-tickle following Rapid Eye Movement sleep dreaming

Self-produced tactile stimulation usually feels less tickly--is perceptually attenuated--relative to the same stimulation produced externally. This is not true, however, for individuals with schizophrenia. Here, we investigate whether the lack of attenuation to self-produced stimuli seen in schizophrenia also occurs for normal participants following REM dreams. Fourteen participants were stimulated on their left palm with a tactile stimulation device which allowed the same stimulus to be generated by the participant or by the experimenter. The level of self-tickling attenuation did not differ between REM and non-REM sleep awakening conditions, where presence or absence of an accompanying dream was not controlled for. However, for the female participants, when awakening occurred from an REM sleep dream, self-stimulation ratings were higher than for external stimulation, whereas ratings after NREM sleep unaccompanied by a dream were lower for self-stimulation than for external stimulation. These results indicate deficits in self-monitoring and a confusion between self- and externally generated stimulation accompany REM dream formation.     

Cognitive and emotional processes during dreaming: a neuroimaging view

Dream is a state of consciousness characterized by internally-generated sensory, cognitive and emotional experiences occurring during sleep. Dream reports tend to be particularly abundant, with complex, emotional, and perceptually vivid experiences after awakenings from rapid eye movement (REM) sleep. This is why our current knowledge of the cerebral correlates of dreaming, mainly derives from studies of REM sleep. Neuroimaging results show that REM sleep is characterized by a specific pattern of regional brain activity. We demonstrate that this heterogeneous distribution of brain activity during sleep explains many typical features in dreams. Reciprocally, specific dream characteristics suggest the activation of selective brain regions during sleep. Such an integration of neuroimaging data of human sleep, mental imagery, and the content of dreams is critical for current models of dreaming; it also provides neurobiological support for an implication of sleep and dreaming in some important functions such as emotional regulation.     

Dreaming without REM sleep

To test whether mental activities collected from non-REM sleep are influenced by REM sleep, we suppressed REM sleep using clomipramine 50mg (an antidepressant) or placebo in the evening, in a double blind cross-over design, in 11 healthy young men. Subjects were awakened every hour and asked about their mental activity. The marked (81%, range 39-98%) REM-sleep suppression induced by clomipramine did not substantially affect any aspects of dream recall (report length, complexity, bizarreness, pleasantness and self-perception of dream or thought-like mentation). Since long, complex and bizarre dreams persist even after suppressing REM sleep either partially or totally, it suggests that the generation of mental activity during sleep is independent of sleep stage.     

Inducing signal-verified lucid dreams in 40% of untrained novice lucid dreamers within two nights in a sleep laboratory setting

Dreams in which the dreamer is aware of the dream state (lucid dreams, LD) are difficult to induce in naïve subjects in-laboratory. Recently, Stumbrys and Erlacher (2014) used a combination of existing induction techniques together with a self-developed experiment protocol and achieved comparatively high LD induction rates. In this study, we simplified their methodology slightly and repeated their experiment with twenty naïve subjects who spent one or two nights in our sleep laboratory. After about six hours of sleep, they were woken up during REM sleep and engaged in a series of cognitive tasks before going back to bed. Ten subjects reported a LD during the following period of sleep in one of the nights. Eight of these subjects gave a predefined eye signal, which was clearly visible in the electrooculogram during REM sleep. In summary, we replicated Stumbrys and Erlacher’s results using a simplified version of their induction protocol.     

Frequency of lucid dreaming in a representative German sample

Lucid dreams occur when a person is aware that he is dreaming while he is dreaming. In a representative sample of German adults (N = 919), 51% of the participants reported that they had experienced a lucid dream at least once. Lucid dream recall was significantly higher in women and negatively correlated with age. However, these effects might be explained by the frequency of dream recall, as there was a correlation of .57 between frequency of dream recall and frequency of lucid dreams. Other sociodemographic variables like education, marital status, or monthly income were not related to lucid dream frequency. Given the relatively high prevalence of lucid dreaming reported in the present study, research on lucid dreams might be pursued in the sleep laboratory to expand the knowledge about sleep, dreaming, and consciousness processes in general.     

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.     

Effects of pyridoxine on dreaming: a preliminary study

The effect of pyridoxine (Vitamin B-6) on dreaming was investigated in a placebo, double-blind study to examine various claims that Vitamin B-6 increases dream vividness or the ability to recall dreams. 12 college students participated in all three treatment conditions, each of which involved ingesting either 100 mg B-6, 250 mg B-6, or a placebo prior to bedtime for a period of five consecutive days. The treatment conditions were completely counterbalanced and a two-day wash-out period occurred between the three five-day treatment blocks. Morning self-reports indicated a significant difference in dream-salience scores (this is a composite score containing measures on vividness, bizarreness, emotionality, and color) between the 250-mg condition and placebo over the first three days of each treatment. The data for dream salience suggests that Vitamin B-6 may act by increasing cortical arousal during periods of rapid eve movement (REM) sleep. An hypothesis is presented involving the role of B-6 in the conversion of tryptophan to serotonin. However, this first study needs to be replicated using the same procedures and also demonstrated in a sleep laboratory before the results can be considered certain.     

Testing the involvement of the prefrontal cortex in lucid dreaming: A tDCS study

Recent studies suggest that lucid dreaming (awareness of dreaming while dreaming) might be associated with increased brain activity over frontal regions during rapid eye movement (REM) sleep. By applying transcranial direct current stimulation (tDCS), we aimed to manipulate the activation of the dorsolateral prefrontal cortex (DLPFC) during REM sleep to increase dream lucidity. Nineteen participants spent three consecutive nights in a sleep laboratory. On the second and third nights they randomly received either 1 mA tDCS for 10 min or sham stimulation during each REM period starting with the second one. According to the participants’ self-ratings, tDCS over the DLPFC during REM sleep increased lucidity in dreams. The effects, however, were not strong and found only in frequent lucid dreamers. While this indicates some preliminary support for the involvement of the DLPFC in lucid dreaming, further research, controlling for indirect effects of stimulation and including other brain regions, is needed.     

Jungian personality typology and the recall of everyday and archetypal dreams

Hypotheses concerning the relations among personality types, neuroticism, and the recall of archetypal dreams were derived from Jungian theory. Dream records were obtained from a nonclinical population in two stages: first, recall of the most recent, most vivid, and earliest remembered dreams (N = 146), and then dream recall on awakening, over an average of 23 nights, from 30 of the first-sample subjects. A total of 697 dreams was recorded. Subjects also completed the Eysenck Personality Inventory (EPI) the Myers-Briggs Personality Inventory, and a Dreaming Questionnaire. Dream archetypality was rated in accordance with procedures of H. Y. Kluger. The distribution of archetypal dreams across earliest (n = 106), most vivid (n = 105), and most recent (n = 102) dream types matched Kluger's earlier results. The dream diary recall data showed that Jungian intuitives, as measured via Myers-Briggs continuous scores, recalled more archetypal dreams; introverts, as measured via Myers-Briggs continuous scores, recalled more everyday dreams; high EPI neuroticism scorers recalled fewer archetypal dreams. The results support several propositions of Jungian personality theory.     

The electrophysiological correlates of dream recall and nonrecall from stage 2 sleep

This research examined the relationship between cortical activation, defined by electroencephalographic (EEG) measures, and the ability to recall dreams following awakenings from Stage 2 sleep. Period-analyzed EEG data from 40 subjects were examined for the preawakening, postawakening, and preawakening-to-postawakening time intervals. Recall differed from nonrecall at the postawakening and preawakening-to-postawakening periods on measures of muscle activity and time spent in the sigma (12-16 Hz) frequency band. There were no distinctions in recall ability on EEG hemispheric asymmetry measures. Generally, the findings do not support the hypothesis linking increased recall ability to increases in cortical activation prior to awakening. However, the recall groups depicted a different pattern of arousal in their transition from sleep to wakefulness.     

Rapid eye movement sleep dreaming is characterized by uncoupled EEG activity between frontal and perceptual cortical regions

EEG coherent activity is involved in the binding of spatially separated but temporally correlated stimuli into whole events. Cognitive features of rapid eye movement sleep (REM) dreaming resemble frontal lobe dysfunction. Therefore, temporal coupling of EEG activity between frontal and perceptual regions was analyzed from 10 min prior to dream reports (8 adults) from stage-2 and REM sleep. EEG correlation between frontal and perceptual regions decreased and, among perceptual regions increased during REM. The temporal dissociation of EEG activity between executive and perceptual regions supplies an inadequate mechanism for the binding and interpretation of ongoing perceptual activity resulting in dream bizarreness.     

Sleep disturbances in the aftermath of trauma and posttraumatic stress disorder

Sleep disturbances, including nightmares and insomnia, are prominent following trauma and with posttraumatic stress disorder (PTSD) and likely contribute to the pathogenesis of the disorder. Findings from laboratory studies of PTSD have been inconsistent in terms of documenting objective impaired sleep maintenance but have been somewhat more consistent in indicating alterations of rapid eye movement (REM) sleep. Studies of the early aftermath of trauma can reduce the complexity associated with chronicity and comorbidity, and may have implications for early diagnosis and prevention. Multiple studies indicate that dream content is affected by recent threatening experiences. The development of PTSD is associated with a more replicative type of nightmare content. Sleep is reported to be generally disrupted following trauma especially among those developing PTSD. The limited number of studies that provide objective recorded indices during the early aftermath of trauma also provide a mixed picture regarding overall sleep maintenance. Recent data suggest that a more specific disruption of REM sleep may be associated with the development of PTSD and that this disruption is associated with an increased signal of sympathetic nervous system activation during REM sleep. Disrupted REM sleep and increased sympathetic/noradrenergic activity may have implications for understanding recent promising interventions for PTSD sleep disturbance that can be applied to early intervention.     

Dream recall, dream length, and sleep duration: state or trait factor

Longer sleep duration should be related to dream recall (longer REM sleep), but previous findings regarding the relationship between habitual sleep duration and dream recall frequency have been conflicting, whereas experimental manipulation of sleep duration yielded a significant effect. The analysis of diaries kept by the 444 participants over 14 days indicated that intra-individual fluctuations and interindividual differences in sleep duration affect dream recall.     

Frontal electroencephalogram alpha asymmetry during sleep: stability and its relation to affective style

Electroencephalogram (EEG) alpha (8-12 Hz) asymmetries were collected from the mid-frontal and central regions during presleep wakefulness and Stage 1, Stage 2, and rapid eye movement (REM) sleep in 11 healthy right-handed participants who were free of psychiatric, neurological, and sleep problems. The authors found significant correlations between presleep wakefulness and different stages of sleep in the frontal, but not central, EEG alpha asymmetry measure. The strongest correlation was between presleep waking and REM sleep, replicating and extending relation earlier work to a normal population. The high degree of association between presleep waking and REM sleep may be a result of high cortical activation common to these states and may reflect a predisposition to different styles of emotional reactivity.     

NonREM sleep mentation in chronically-treated persons with schizophrenia

This study examined the laboratory dream content reported by 14 patients with schizophrenia and 15 controls, with a focus on reports obtained from NonREM sleep. Both the controls' and patients' frequency of dream recall following awakenings from NonREM and REM sleep were similar to values reported for healthy participants. Patients' NonREM sleep narratives were shorter than those from controls. When compared to their reports from REM sleep, both groups' NonREM sleep reports included significantly fewer words and reportable items. The controls were more likely to report a subjective feeling of bizarreness for their REM sleep reports as compared to their NonREM sleep reports. This difference was not observed in patients with schizophrenia. Taken together, these findings suggest few differences between the NonREM sleep mentation of patients with schizophrenia and of controls and that sleep stage cognitive style is comparable in both groups, with NonREM sleep reports being more thought-like, less elaborate and bizarre than REM sleep reports.