Story-like organization of REM-dreams in patients with narcolepsy-cataplexy

Narcolepsy with cataplexy (NC) is a neurological disorder characterized by excessive daytime sleepiness and an altered architecture of sleep. Previous laboratory studies have shown that frightening, bizarre and visually vivid contents are more frequent in dream experiences developed during the first period of REM sleep by NC patients than healthy subjects. As the structural organization of dream experiences of NC patients has not been yet examined, we compared its indicators in dream reports collected from a sample of NC patients and their matched controls. During an experimental night two awakenings were provoked after 8min of REM sleep in the first and third sleep cycle. Dream reports were analyzed using the rules of story grammars, capable of identifying units larger than single contents and describing their story-like organization. While dream recall (about 85%) was comparable in NC patients and controls, 1st-REM dream reports were longer in NC patients. Statistical analyses on the 12 NC patients and their matched controls who reported dreams after both REM periods showed that dream experiences occurring in 1st-REM reports of NC patients were longer and had a more complex organization than those of controls. These findings suggest that the cognitive processes underlying dream generation reach their optimal functioning earlier in the night in NC patients than in normal subjects.     

Dream recall frequency in epilepsy patients with partial and generalized seizures: a dream diary study

PURPOSE: The frequency of dream recall (DR) in patients with brain diseases has proved to be indicative of the relation between sleep disturbances and the functioning of cognitive processes during sleep. In this study we attempted to ascertain whether DR frequency in patients with complex partial seizures (CPSs) is higher than that in those with generalized seizures. METHODS: DR frequency was assessed by means of a 60-day dream diary in patients with CPSs, whose epileptic focus was in the right (n = 12) or left temporal lobe (n = 28), and with idiopathic generalized seizures (n = 21). The patients enrolled in the study were not impaired in global cognitive and memory functioning. RESULTS: The ability to recall dreams was established in nearly all patients with either CPSs or generalized seizures. DR frequency resulted significantly higher (about twice) in patients with CPSs, regardless of (a) the side of the epileptic focus, (b) the presence of a cerebral lesion detectable on a computed tomography (CT) scan, or (c) the occurrence of seizures in the previous day. CONCLUSIONS: These findings indicate that overall, DR occurs in medicated epilepsy patients with CPSs more frequently than reported in previous studies. The high DR frequency observed in these patients, regardless of the side of the epileptic focus, is in agreement with the assumption that tempoparietal areas of both hemispheres are involved in the production and recall of the dream experience.     

REM-dreams recall in patients with narcolepsy-cataplexy

An abundant recall of dreams has been observed in clinical studies on patients with narcolepsy-cataplexy (NC), a neurological disorder characterized by an altered sleep architecture. Laboratory studies have shown that dream experiences developed during 1st-rapid eye movement (REM) sleep by NC patients are longer and more complex than those of healthy subjects. To establish whether these features indicate an earlier optimal functioning of the cognitive processes involved in dream generation rather than a more accurate dream recall, we compared the indicators of length and structural organization in reports of REM-dreams collected from 14 NC patients and their matched controls. During an experimental night two awakenings were provoked after 8 min in 1st- and 3rd-REM sleep; participants were asked to report their dream experience (spontaneous report) and then, if possible, further remembered parts of this experience (prompted report). All reports were analyzed using story-grammar rules, which allow us to identify units larger than single contents and describe their story-like organization. While dream recall (about 90%) was comparable in NC patients and controls, 1st-REM spontaneous reports were longer and more complex in NC patients, half of whom also provided prompted reports. After 3rd-REM awakening more than one third of NC patients and controls gave prompted reports, which were fairly comparable in length and complexity with the spontaneous reports. These findings confirm that the cognitive processes underlying dream generation reach their optimal functioning earlier in the night in NC patients than in normal subjects, and raises the question of whether the dream-stories described in spontaneous and prompted reports are part of the same or distinct REM-dreams.     

EEG activities during elicited sleep onset REM and NREM periods reflect different mechanisms of dream generation. Electroencephalograms. Rapid eye movement.

OBJECTIVE: To be the first to compare EEG power spectra during sleep onset REM periods (SOREMP) and sleep onset NREM periods (NREMP) in normal individuals and relate this to dream appearance processes underlying these different types of sleep periods. METHODS: Eight healthy undergraduates spent 7 consecutive nights in the sleep lab including 4 nights for SOREMP elicitation using the Sleep Interruption Technique. This enabled us to control preceding sleep processes between SOREMP and NREMP. EEG power spectra when participants did and did not report 'dreams' were compared between both types of sleep. Sleep stages, subjective measurements including dream property scores, sleepiness, mood, and tiredness after awakenings were also examined to determine their consistency with EEG findings. RESULTS: Increased alpha EEG activities (11.72-13.67 Hz) observed mainly in the central area were related to the absence of SOREMP dreams and appearance of NREMP dreams. Analyses of sleep stages combining two studies (16 participants) also supported the Fast Fourier Transform findings, showing that when dreams were reported there were decreased amounts of stage 2 and increased stage REM in SOREMP and increased stage W in NREMP. SOREMP dreams were more bizarre than NREMP dreams. Participants felt more tired after SOREMP with dreams than without dreams, while the opposite was observed after NREMP episodes. CONCLUSIONS: EEG power spectra patterns reflected different physiological mechanisms underlying generation of SOREMP and NREMP dreams. The same relationships were also reflected by sleep stage analyses as well as subjective measurements including dream properties and tiredness obtained after awakenings. This study not only supports the hypothesized relationships between REM mechanisms and REM dreams as well as arousal processes and NREM dreams, it also provides a new perspective to dream research due to its unique techniques to awaken participants and collect REM dreams during experimentally induced SOREMP.     

Mental activity after early afternoon nap awakenings in healthy subjects

Despite the common misconception that rapid eye movement (REM) sleep is a unique correlate of dreaming, reports of mental activity can be elicited after awakenings from any stage of nocturnal sleep. We extended the investigation to naps and tried to explore the relationship between recall length and level of sleep stage and depth preceding the awakening. We hypothesized that dream report length would be related to arousal level. In 10 healthy young adults, sleep EEG and EOG were recorded for four non-consecutive early afternoon naps. Dream recalls were recorded following 10 s, 1 min, and 6 min of NREM Stage 2 and after 5 min of first REM period. We measured mental recall with total word count (TWC) method, sleep stages by using EEG visual scoring and Delta and Beta activity by period amplitude (PAA) and power spectral (PSA) analyses. All awakening conditions were followed by a dream report. TWC was significantly greater after REM than after 10 s and 1 min of NREM, and TWC did not differ among the NREM awakenings. Delta activity after REM was significantly lower compared to the NREM 6 and 1 min while Beta activity did not differ across the conditions. Assuming that arousal level decreased with increased NREM duration and increasing Delta EEG activity, the constant TWC across the three NREM awakenings indicates that arousal level cannot be the only factor affecting dream report length. Some other factor such as memory processing may explain the longer dream reports following REM sleep, or it may be that the EEG is an imperfect indicator of arousal level.     

Appearance of frontal mid-line theta rhythm during sleep and its relation to mental activity

Fm theta occurred not only during mental tests in the waking state but also during nocturnal sleep in which it was most frequent during REM and secondarily most frequent during stage 1 of NREM sleep. As for the inner experience of the subjects, they frequently reported dream and distinct mentations on awakening from REM sleep whether or not it was accompanied by Fm theta. They reported dream and distinct mentations more frequently when awakened from stage 1 of NREM sleep with Fm theta than when awakened from stage 1 of NREM sleep without Fm theta. Relationship of Fm theta to mental activity during sleep was briefly discussed.     

Comparative analysis of multiple sleep latency tests (MSLT) parameters and occurrence of dreaming in patients with daytime sleepiness of narcoleptic and non-narcoleptic origin

OBJECTIVE: To compare MSLT parameters in two groups of patients with daytime sleepiness, correlated to the occurrence and onset of dreams. METHOD: Patients were submitted to the MSLT between January/1999 and June/2002. Sleep onset latency, REM sleep latency and total sleep time were determined. The occurrence of dreams was inquired following each MSLT series. Patients were classified as narcoleptic (N) or non-narcoleptic (NN). RESULTS: Thirty patients were studied, 12 were classified as narcoleptics (N group; 40%), while the remaining 18 as non-narcoleptic (NN group; 60%). Thirty MSLT were performed, resulting in 146 series. Sleep was detected in 126 series (86%) and dreams in 56 series (44.44%). Mean sleep time in the N group was 16.0+/-6.3 min, while 10.5+/-7.5 min in the NN group (p<0.0001). Mean sleep latency was 2.0+/-2.2 min and 7.2+/-6.0 min in the N and NN group, respectively (p<0.001). Mean REM sleep latency in the N group was 3.2+/-3.1min and 6.9+/-3.7 min in the NN group (p=0.021). Dreams occurred in 56.9% of the N group series and 28.4% in that of the NN group (p=0.0009). Dream frequency was detected in 29.8% and 75% of the NREM series of the N and NN groups, respectively (p=0.0001). CONCLUSION: Patients from the N group, compared to the NN group, slept longer and earlier, demonstrated a shorter REM sleep onset and greater dream frequency. NN patients had a greater dream frequency in NREM series. Thus, the occurrence of dreams during NREM in the MSLT may contribute to differentially diagnose narcolepsy and daytime sleepiness.     

Dream recall and Dream Content in Children with Attention Deficit/Hyperactivity Disorder

Although sleep is widely investigated in children with ADHD, dream studies in this group are completely lacking. The continuity hypothesis of dreaming stating that waking life is reflected in dreams would predict that waking-life symptoms are reflected in the dreams of such children. 103 children with ADHD and 100 controls completed a dream questionnaire eliciting dream recall frequency and the most recent dream. The dreams of the children with ADHD did not show a heightened occurrence of activities but were more negatively toned and included more misfortunes/threats, negative endings, and physical aggression towards the dreamer. Dream recall frequency and general dream characteristics like dream length and dream bizarreness did not differ from children without ADHD. The dreams seem to reflect the inner world of the child with ADHD. From a clinical point of view, it would be very interesting to study whether the negatively toned dreams change during treatment (pharmacological and/or psychotherapeutic) in a way similar to how sleep quality improves.     

Dream structure in Parkinson's patients.

Dream reports of patients with Parkinson's disease (PD) were analyzed to ascertain whether cognitive deficits associated with this nonfocal brain pathology influence dream structure or dream recall. Fifteen outpatients with idiopathic PD were sampled (diagnosed from 1 to 10 years and currently in stage II or III of Hoehn and Yarh's scale); all were without psychiatric symptoms or major medical illnesses and were currently being treated with L-dopa. After an adaptation night in the sleep laboratory, each patient spent a night in which he/she was awakened at least twice in rapid eye movement sleep and asked to report dream experience. Thirteen patients were able to report at least one dream. Overall frequency of dream recall (71.4%) was fully compatible with normative data for the elderly. Multiple regression analyses showed that both the length of the dream report as story and the organization of contents into coherent episodes (analyzed using Mandler and Johnson's story grammar) varied significantly in relation to level of cognitive functioning and, in part, of language comprehension, but not in relation to age, illness duration, and dose of L-dopa.     

REM dream activity of insomnia sufferers: a systematic comparison with good sleepers

Background and ObjectiveThe dream activity of patients with primary insomnia (PI) has rarely been studied, especially using in-laboratory dream collection, although dreams could be linked to their state of hyperarousal and their negative waking experiences. The objective of the study was to compare patients with PI and good sleeper controls (GSCs) in terms of dream recall frequency and dream content.Patients/MethodsPolysomnography was recorded in 12 patients with PI and 12 GSCs (aged between 30 and 45 years) for five consecutive nights. Rapid eye movement (REM) sleep awakenings were enforced on nights 3 and 5 for dream collections.ResultsThe REM dream collections revealed that the groups were similar in terms of dream recall frequency (p ≤ 0.7). With respect to dream content variables, the dreams of GSCs tended to comprise more positive emotions (p = 0.06), whereas the dreams of patients with PI were characterized by more negative elements than positive ones (p = 0.001). Subjectively, GSCs characterized their dreams as being more pleasant and containing more joy, happiness, and vividness (p ≤ 0.03) than patients with PI. Finally, elevated negative dream content was associated with lower sleep efficiencies in insomnia (p = 0.004).ConclusionThese results suggest that less positive emotions and greater negative content characterize the dreams of patients with PI, which is in line with their waking experiences. One potential explanation could be hyperarousal exacerbating presleep negative mentation, thus contributing to poorer sleep quality. The lack of difference in dream recall frequency is most likely due to the forced awakening “dream collection” procedure. The study of dream activity seems a promising avenue for understanding the 24-h experience of insomnia better and exploring the potential benefits of dream management techniques.     

Dream process in asthmatic subjects with nocturnal attacks

Polygraphic sleep recordings were made and dream reports collected over 3 consecutive nights for 12 asthmatic subjects with nocturnal attacks and 12 matched normal control subjects. The asthmatic group 1) had more episodes of a vivid impression of dreaming without recollection of dream content ("white dreams") after awakening spontaneously in the morning (nights 1 and 2) and after awakening immediately following REM sleep (night 3), 2) used shorter sentences in dream narrations, and 3) had no dream recall when awakened during nocturnal asthma attacks. The authors suggest that conflictual material emerging during REM or other sleep stages may contribute to the occurrence of nocturnal attacks but is repressed on awakening.     

Sleep and dreams in Korsakoff's amnesia due to alcoholism

Sleep and dreams in 15 chronic alcoholic patients with amnesia were compared with sleep and dreams of 15 age- and sex-adjusted normal subjects. The patients were subjected to psychological tests in order to determine their I.Q. and their memory disturbances. All subjects had two nights of polygraphic recordings; the first tested the natural sleep organization. During the second night, they were awakened 7 min after the onset of each REM sleep episode, and, at least once, 20 min after the onset of a stage II episode, in order to record on a tape their dream reports according to a standardized protocol. The sleep patterns of the amnesic patients did not show any significant alteration. However, after wakening during the night, patients exhibited a higher tendency to return to REMS than controls. There was still some dream activity in those patients, although noticeably less frequently, and their dream activity had a very poor verbal expression. However, there was no change with respect to the spatio-temporal organization, sensorial perceptions, motor activity and verbalizations during their dreams.     

Coherent neocortical 40‐Hz oscillations are not present during REM sleep

During cognitive processes there are extensive interactions between various regions of the cerebral cortex. Oscillations in the gamma frequency band (≈40 Hz) of the electroencephalogram (EEG) are involved in the binding of spatially separated but temporally correlated neural events, which results in a unified perceptual experience. The extent of these interactions can be examined by means of a mathematical algorithm called ‘coherence’, which reflects the ‘strength’ of functional interactions between cortical areas. The present study was conducted to analyse EEG coherence in the gamma frequency band of the cat during alert wakefulness (AW), quiet wakefulness (QW), non‐rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Cats were implanted with electrodes in the frontal, parietal and occipital cortices to monitor EEG activity. Coherence values within the gamma frequency (30–100 Hz) from pairs of EEG recordings were analysed. A large increase in coherence occurred between all cortical regions in the 30–45 Hz frequency band during AW compared with the other behavioral states. As the animal transitioned from AW to QW and from QW to NREM sleep, coherence decreased to a moderate level. Remarkably, there was practically no EEG coherence in the entire gamma band spectrum (30–100 Hz) during REM sleep. We conclude that functional interactions between cortical areas are radically different during sleep compared with wakefulness. The virtual absence of gamma frequency coherence during REM sleep may underlie the unique cognitive processing that occurs during dreams, which is principally a REM sleep‐related phenomenon.     

Unaltered EEG spectral power and functional connectivity in REM microstates in frequent nightmare recallers: are nightmares really a REM parasomnia?

BackgroundFrequent nightmares show signs of hyperarousal in NREM sleep. Nevertheless, idiopathic nightmare disorder is considered a REM parasomnia, but the pathophysiology of REM sleep in relation to frequent nightmares is controversial. Cortical oscillatory activity in REM sleep is largely modulated by phasic and tonic REM periods and seems to be linked to different functions and dysfunctions of REM sleep. Here, we examined cortical activity and functional synchronization in frequent nightmare recallers and healthy controls, during phasic and tonic REM.MethodsFrequent nightmare recallers (N = 22) and healthy controls (N = 22) matched for high dream recall spent two nights in the laboratory. Phasic and tonic REM periods from the second nights' recordings were selected to examine differences in EEG spectral power and weighted phase lag index (WPLI) across groups and REM states.ResultsPhasic REM showed increased power and synchronization in delta and gamma frequency bands, whereas tonic REM featured increased power and synchronization in the alpha and beta bands. In the theta band, power was higher during tonic, and synchronization was higher during phasic REM sleep. No differences across nightmare and control participants or patterns representing interactions between the groups and REM microstates emerged.ConclusionsOur findings do not support the idea that abnormal REM sleep power and synchronization play a role in the pathophysiology of frequent nightmares. Altered REM sleep in nightmare disorder could have been confounded with comorbid pathologies and increased dream recall, or might be linked to more specific state factors (nightmare episodes).     

Non-dreamers

OBJECTIVE: Assess incidence and clarify whether diagnostic correlates exist for sleep laboratory patients reporting a lack of dream recall. To awaken, during polysomnographically defined sleep including rapid eye movement (REM) sleep, individuals reporting never having experienced a dream, and determine whether they report dreaming. METHODS: Study # 1 - Incidence and polysomnographic correlates of sleep lab patients responding on questionnaire that they had never experienced dreaming. Study # 2 - Phone interviews with those individuals reporting non-dreaming on questionnaire to reassess incidence. Study # 3 - After reassessment, individuals (non-dreamers - # 16) are awakened during polysomnographic defined sleep (including REM sleep) and queried about dream recall. This group is compared statistically to a group (rare-dreamers - # 12) that reported dreaming as an extremely rare occurrence (mean dream recall latency - 13.5 years). RESULTS: Study # 1: Incidence of questionnaire reported non-dreaming in this sleep laboratory population is 6.5% (N=534) and is associated with the diagnosis of obstructive sleep apnea (specificity 95.6% for respiratory disturbance index >15). Study # 2 - Individuals who report after interview to have never experienced dreaming are more unusual (0.38% of this sleep laboratory population). Study # 3 - None of the non-dreamers (# 16) reported dream recall after waking in the sleep laboratory (36 awakenings in total for this group). This group does not differ, based on polysomnographic, clinical, or demographic variables, from the rare-dreaming group that occasionally reported dreams when awakened (3/12 patients, 3/32 awakenings) - a finding consistent with the reports of previous studies. CONCLUSION: The experience of dreaming may not be as ubiquitous as generally accepted. The group of non-dreamers evaluated in this study reports never having recalled a dream and reports no dreams when awakened during polysomnographicly defined sleep. These individuals might not experience dreaming.     

Sleep‐related hypermotor epilepsy activated by rapid eye movement sleep

Most sleep‐related seizures occur during non‐rapid eye movement (NREM) sleep, particularly during stage changes. Sleep‐related hypermotor epilepsy (SHE) is a rare epileptic syndrome characterized by paroxysmal motor seizures, mainly arising from NREM sleep. Here, we report a patient with SHE who had seven seizures captured on video‐EEG‐polysomnography during REM sleep. Ictal semiology of this patient ranged from brief paroxysmal arousals to hypermotor seizures. On EEG‐polysomnography, the spontaneous arousals were more frequent during REM than NREM sleep, with a considerably higher arousal index in REM sleep (20/hour). While the reason for seizures during REM sleep in this patient is unclear, we speculate that the threshold and mechanisms of arousal during different sleep stages may be related to the occurrence of seizures. [Published with video sequences on www.epilepticdisorders.com ].     

Relationship of interictal epileptiform discharges to sleep depth in partial epilepsy

Non-rapid eye movement (NREM) sleep activates interictal epileptiform discharges (spikes) in many epileptic syndromes. To define this phenomenon more precisely, we studied the relationship of spikes to absolute log delta power (LDP), a continuous measure of sleep depth, in 8 patients with partial epilepsy. LDP differed significantly across visually scored sleep stages. Logistic regression analyses of spike occurrence in relation to LDP were carried out on the central-occipital channel contralateral to the dominant spike focus (C4-O2 for left and C3-O1 for right temporal focus). Within NREM sleep, spikes were more likely to occur: (1) at higher levels of LDP, (2) on the ascending limb of LDP, and (3) with more rapid rises in LDP. Spike frequency per minute was 4.6 times higher in NREM than in rapid-eye movement (REM) sleep and diminished with time from sleep onset. When the effect of LDP was controlled for in the analysis, however, there was no significant effect of REM sleep stage or time on spike occurrence. Only 1% of spikes occurred within 10 s of an arousal. These findings suggest that processes underlying the deepening of NREM sleep may contribute to spike activation in partial epilepsy.     

Sleep states and memory processes in humans: procedural versus declarative memory systems

The present paper focuses on human studies attempting to relate sleep states to memory processes. These studies typically present learning material to participants and then examine their ability to recall this material after intervening post-training sleep or sleep deprivation. Most experiments utilize either sleep recording or sleep deprivation following task acquisition to reach their conclusions, although cueing and position emission tomography (PET) scan studies have also been done. Results strongly suggest that REM sleep is involved with the efficient memory processing of cognitive procedural material but not declarative material. Although there are some data to suggest that stage 3/4 or NREM sleep is necessary for declarative memory consolidation, NREM may in fact simply be occurring at the same time as another factor that is actually involved in the memory processing. Preliminary results suggest that the length of the NREM–REM sleep cycle may be important for declarative memory. Preliminary data also suggest that stage 2 sleep may be involved with the memory for motor procedural but not cognitive procedural tasks. Sleep researchers would do well to capitalize on the latest advancements in memory research by choosing tasks that represent special memory systems and examining their relationships to sleep states.     

REM sleep instability--a new pathway for insomnia?

Chronic insomnia afflicts approximately 10% of the adult population and is associated with daytime impairments and an elevated risk for developing somatic and mental disorders. Current pathophysiological models propose a persistent hyperarousal on the cognitive, emotional and physiological levels. However, the marked discrepancy between minor objective alterations in standard parameters of sleep continuity and the profound subjective impairment in patients with insomnia is unresolved. We propose that "instability" of REM sleep contributes to the experience of disrupted and non-restorative sleep and to the explanation of this discrepancy. This concept is based on evidence showing increased micro- and macro-arousals during REM sleep in insomnia patients. As REM sleep represents the most highly aroused brain state during sleep it seems particularly prone to fragmentation in individuals with persistent hyperarousal. The continuity hypothesis of dream production suggests that pre-sleep concerns of patients with insomnia, i. e., worries about poor sleep and its consequences, dominate their dream content. Enhanced arousal during REM sleep may render these wake-like cognitions more accessible to conscious perception, memory storage and morning recall, resulting in the experience of disrupted and non-restorative sleep. Furthermore, chronic fragmentation of REM sleep might lead to dysfunction in a ventral emotional neural network, including limbic and paralimbic areas that are specifically activated during REM sleep. This dysfunction, along with attenuated functioning in a dorsal executive neural network, including frontal and prefrontal areas, might contribute to emotional and cognitive alterations and an elevated risk of developing depression.