Motivation and affect in REM sleep and the mentation reporting process

Although the emotional and motivational characteristics of dreaming have figured prominently in folk and psychoanalytic conceptions of dream production, emotions have rarely been systematically studied, and motivation, never. Because emotions during sleep lack the somatic components of waking emotions, and they change as the sleeper awakens, their properties are difficult to assess. Recent evidence of limbic system activation during REM sleep suggests a basis in brain architecture for the interaction of motivational and cognitive properties in dreaming. Motivational and emotional content in REM and NREM laboratory mentation reports from 25 participants were compared. Motivational and emotional content was significantly greater in REM than NREM sleep, even after controlling for the greater word count of REM reports.     

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.     

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.     

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.     

Posttraining increases in REM sleep intensity implicate REM sleep in memory processing and provide a biological marker of learning potential

Posttraining rapid eye movement (REM) sleep has been reported to be important for efficient memory consolidation. The present results demonstrate increases in the intensity of REM sleep during the night of sleep following cognitive procedural/implicit task acquisition. These REM increases manifest as increases in total number of rapid eye movements (REMs) and REM densities, whereas the actual time spent in REM sleep did not change. Further, the participants with the higher intelligence (IQ) scores showed superior task acquisition scores as well as larger posttraining increases in number of REMs and REM density. No other sleep state changes were observed. None of the pretraining baseline measures of REM sleep were correlated with either measured IQ or task performance. Posttraining increases in REM sleep intensity implicate REM sleep mechanisms in further off-line memory processing, and provide a biological marker of learning potential.     

EEG asymmetry and sleep mentation during REM and NREM

The hypothesis that dreaming is mediated by the right hemisphere was evaluated by monitoring EEG power asymmetry during REM and NREM sleep, and obtaining mentation reports when short-term temporal shifts in the EEG indicated relative left- or right-hemispheric dominance. Content analyses provided no support for the right-hemisphere hypothesis; indeed, some scales showed higher content during relative left-hemispheric dominance. In contrast to earlier reports, no difference between REM and NREM in EEG asymmetry was observed.     

Configuration of the dream in REM sleep

Dreams during REM sleep have a characteristic form. They are, so to speak, "chain dreams, in which the scenes follow consecutively and, although distinctly separate from each other, are welded into a coherent dream by the primary integrating thoughts underlying the dream. The contents of the different scenes are difficult to reconcile with the integrating thought behind the dream because they are not stimulated by the thought alone but, in a certain way, also by past experiences. The author describes a dream which apparently filled the REM phase from beginning to end. It has been possible to explain the background of the integrating thought and the origins of the different scenes. The peculiar character of such dreams should find more attention in scientific research.     

REM sleep: A social bonding mechanism

It is proposed that REm sleep evolved, in part, to promote social bonding between (1) a mammalian infant and the mother and (2) sexual partners. The bonding hypothesis is consistent with the available evidence from psychobiologic studies of the attachment process in infants, with the known physiologic correlates of REM sleep, with the facts concerning the ontogeny and the phylogeny of REM sleep, and with phenomenological properties of dreams.     

Attachment, sleep quality, and depressed affect.

This study examined the role of attachment insecurity in sleep problems among married adults (N=78 couples). Using the Pittsburgh Sleep Quality Index and structural equation modeling, attachment anxiety was associated with higher levels of self-reported sleep difficulties for men and women, whereas attachment avoidance was not. Depressed affect was included as a control variable, and the effect of attachment anxiety remained significant. Men and women did not differ significantly in the magnitude of the effect of attachment anxiety on sleep quality. In addition, there were no cross-partner effects of attachment insecurity on sleep quality or depressed affect. Implications and future directions are discussed.     

The case against memory consolidation in REM sleep

We present evidence disputing the hypothesis that memories are processed or consolidated in REM sleep. A review of REM deprivation (REMD) studies in animals shows these reports to be about equally divided in showing that REMD does, or does not, disrupt learning/memory. The studies supporting a relationship between REM sleep and memory have been strongly criticized for the confounding effects of very stressful REM deprivation techniques. The three major classes of antidepressant drugs, monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs), profoundly suppress REM sleep. The MAOIs virtually abolish REM sleep, and the TCAs and SSRIs have been shown to produce immediate (40-85%) and sustained (30-50%) reductions in REM sleep. Despite marked suppression of REM sleep, these classes of antidepressants on the whole do not disrupt learning/memory. There have been a few reports of patients who have survived bilateral lesions of the pons with few lingering complications. Although these lesions essentially abolished REM sleep, the patients reportedly led normal lives. Recent functional imaging studies in humans have revealed patterns of brain activity in REM sleep that are consistent with dream processes but not with memory consolidation. We propose that the primary function of REM sleep is to provide periodic endogenous stimulation to the brain which serves to maintain requisite levels of central nervous system (CNS) activity throughout sleep. REM is the mechanism used by the brain to promote recovery from sleep. We believe that the cumulative evidence indicates that REM sleep serves no role in the processing or consolidation of memory.     

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.     

A review of mentation in REM and NREM sleep: "covert" REM sleep as a possible reconciliation of two opposing models

Numerous studies have replicated the finding of mentation in both rapid eye movement (REM) and nonrapid eye movement (NREM) sleep. However, two different theoretical models have been proposed to account for this finding: (1) a one-generator model, in which mentation is generated by a single set of processes regardless of physiological differences between REM and NREM sleep; and (2) a two-generator model, in which qualitatively different generators produce cognitive activity in the two states. First, research is reviewed demonstrating conclusively that mentation can occur in NREM sleep; global estimates show an average mentation recall rate of about 50% from NREM sleep--a value that has increased substantially over the years. Second, nine different types of research on REM and NREM cognitive activity are examined for evidence supporting or refuting the two models. The evidence largely, but not completely, favors the two-generator model. Finally, in a preliminary attempt to reconcile the two models, an alternative model is proposed that assumes the existence of covert REM sleep processes during NREM sleep. Such covert activity may be responsible for much of the dreamlike cognitive activity occurring in NREM sleep.     

Eye movements during REM sleep: the influence of personality and presleep conditions.

Male subjects scoring high (n=17) or low (n=14) on the Maudsley Neuroticism scale were randomly assigned to a positive (n=17) or negative (ego threat) (n=14) presleep condition and then slept a single night in the laboratory. The negative condition elicited significantly more rapid eye movement activity (REM density) than did the positive condition (pless than.03). There was a significant interaction for Groups X Conditions (pless than.007) indicating that low neuroticism subjects had greater REM density in the negative condition, and less REM density in the positive condition, compared to high neuroticism subjects under either condition. The low neuroticism subjects in the negative condition showed a discrepancy between greater REM density but less admission of stress on a presleep mood questionnaire compared to high neuroticism subjects. These results support the hypothesis that REM density is a correlate of stress-induced arousal that is subject to the modifying effects of individual differences.