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.     

Operant conditioning of eye movement in the monkey (Macaca nemestrina)

With the horizontal electrooculographic potential as the operant, four monkeys (Macaca nemestrina) were conditioned to move their eyes at high and low rates by initial use of fixed-ratio schedules of reinforcement, followed by a changeover to multiple schedules of fixed-ratio reinforcement and discriminated differential reinforcement of low rate. These differences in rate of eye movement were not observed in a control animal given the same patterns of discriminative stimuli and deliveries of the reinforcing agent independent of its eye movements.     

Rapid eye movement sleep deprivation affects sleep similarly in castrated and noncastrated rats

Twenty-four-hour recordings of electrophysiological correlates of the sleep-waking cycle in castrated and noncastrated Wistar rats were performed to validate the cuff pedestal technique in the deprivation of rapid eye movement sleep. An undisturbed pattern of sleep was found in both castrated and noncastrated rats when the cuffs were in the raised position. The lowering of the cuff for 4 days virtually abolished REMs in both groups of rats. During neither the dark nor the light period was there any difference between the castrated and noncastrated rats in the total amount of REMs rebound. The results accord with the data obtained by the conventional flowerpot procedure and show that castration does not influence the amount of REMs before, during, and after REMs deprivation in the rat. It is suggested that testicular testosterone, contrary to growth hormone, is not essential for the triggering of REMs sleep, although both have anabolic actions.     

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.     

Rapid eye movement (REM) in premature neonates and developmental outcome at 6 months

Different aspects of early sleep organization have been associated with subsequent development in premature infants. The aim of the present study was to assess the relations between rapid eye movement (REM) activity in premature neonates and infants' developmental outcomes at 6 months. Participants were 81 premature infants (47 males). Sleep-wake states and REM were observed across 4 consecutive evening hours (7-11 PM) in 10-s frames when infants were between 32 and 36 weeks post-menstrual age. Developmental outcome was assessed at 6 months with the mental development index (MDI) of the Bayley II. Infants with low-REM activity spent more time in less growth-promoting states, including crying and unfocused alert states in the neonatal period and had lower MDI scores at 6 months corrected age compared to infants with high-REM. Differences between the high- and low-REM groups were independent of neonatal medical risk. Low-REM activity may serve as an indicator of developmental risk among premature neonates.     

Emotional memory formation is enhanced across sleep intervals with high amounts of rapid eye movement sleep

Recent studies indicated a selective activation during rapid eye movement (REM) sleep of the amygdala known to play a decisive role in the processing of emotional stimuli. This study compared memory retention of emotional versus neutral text material over intervals covering either early sleep known to be dominated by nonREM slow wave sleep (SWS) or late sleep, in which REM sleep is dominant. Two groups of men were tested across 3-h periods of early and late sleep (sleep group) or corresponding retention intervals filled with wakefulness (wake group). Sleep was recorded polysomnographically. Cortisol concentrations in saliva were monitored at acquisition and retrieval testing. As expected, the amount of REM sleep was about three times greater during late than during early retention sleep, whereas a reversed pattern was observed for SWS distribution (P<0.001). Sleep improved retention, compared with the effects of wake intervals (P<0.02). However, this effect was substantial only in the late night (P<0.005), during which retention was generally worse than during the early night (P<0.02). Late sleep particularly enhanced memory for emotional texts. This effect was highly significant in comparison with memory for neutral texts (P<0.01) and in comparison with memory after late and early wake intervals (P<0.001). Cortisol concentration differed between early and late retention intervals but not between sleep and wake conditions. Results are consonant with a supportive function of REM sleep predominating late sleep for the formation of emotional memory in humans.     

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.     

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.     

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.     

Spatial and reversal learning in the Morris water maze are largely resistant to six hours of REM sleep deprivation following training

This first test of the role of REM (rapid eye movement) sleep in reversal spatial learning is also the first attempt to replicate a much cited pair of papers reporting that REM sleep deprivation impairs the consolidation of initial spatial learning in the Morris water maze. We hypothesized that REM sleep deprivation following training would impair both hippocampus-dependent spatial learning and learning a new target location within a familiar environment: reversal learning. A 6-d protocol was divided into the initial spatial learning phase (3.5 d) immediately followed by the reversal phase (2.5 d). During the 6 h following four or 12 training trials/day of initial or reversal learning phases, REM sleep was eliminated and non-REM sleep left intact using the multiple inverted flowerpot method. Contrary to our hypotheses, REM sleep deprivation during four or 12 trials/day of initial spatial or reversal learning did not affect training performance. However, some probe trial measures indicated REM sleep-deprivation-associated impairment in initial spatial learning with four trials/day and enhancement of subsequent reversal learning. In naive animals, REM sleep deprivation during normal initial spatial learning was followed by a lack of preference for the subsequent reversal platform location during the probe. Our findings contradict reports that REM sleep is essential for spatial learning in the Morris water maze and newly reveal that short periods of REM sleep deprivation do not impair concurrent reversal learning. Effects on subsequent reversal learning are consistent with the idea that REM sleep serves the consolidation of incompletely learned items.     

Cardiac arrhythmias in the monkey during classically conditioned fear and excitement

Rhesus monkeys(Macaca mulatto) were tested in classic aversive and appetitive conditioning paradigms following complete coronary artery occlusion (CO) to test the hypothesis that “emotional stress” induces ventricular arrhythmias. Findings were based upon conditioning trials conducted for one or more weeks after occlusion in 13 animals. When all data from each animal for the week following CO were considered, there was no demonstrable tendency for arrhythmias to increase during “fear” conditioned to unavoidable electric shock or during “excitement” in anticipation of food. However, selected trials from six monkeys did reveal instances when changes in the frequency of occurrence of arrhythmias were coupled with behavioral conditioning. While analysis of these trials did not reveal any simple relationship between emotional stress and the development of ventricular arrhythmias after myocardial infarction, certain of the behavioral situations may be more potentially arrhythmogenic than others. For these selected trials, with respect to control, the number of arrhythmias may have increased or decreased upon presentation of the conditional stimulus; the exact response appears to depend upon the immediate physiologic status of the animal as well as on the behavioral condition. “More stressful” situations, such as aversive conditioning, are not necessarily associated with greater numbers of arrhythmias than were “less stressful” situations, such as appetitive conditioning. Arrhythmias appear to occur more frequently when an animal’s heart rate is within a given range; this may reflect underlying cardiac sympathetic and parasympathetic nerve activity.     

Social factors and the psychobiology of depression: relations between life stress and rapid eye movement sleep latency.

We examined psychosocial factors (i.e., life stress) and biological factors (i.e., REM sleep latency) that are hypothesized to be of complementary importance for defining depressive subtypes in a sample of 61 nonpsychotic, endogenous major depressives. Subjects were evaluated on several diagnostic scales for life stress, on electroencephalographic sleep data, and on 2 symptom measures for depression. As predicted, persons with severe stress that occurred shortly before depression onset had essentially normal REM latency values; patients without such stress had reduced REM latency values. Both stress and REM latency were also associated with greater severity of self-reported depressive symptoms. Alternative explanations of these findings are discussed, with particular emphasis on different roles of pre-onset and post-onset stressors.     

Perceived movement of the afterimage during eye movements

The question of whether an afterimage viewed in a dark field appears to move during eye movement was studied by comparing recordings of eye movements with recordings of reports of perceived movement. The correlation was found to be quite good even under conditions where the eye movements were spontaneous rather than specifically directed. The results were taken to support the hypothesis that the behavior of the retinal image is “interpreted” by taking into account information concerning what the eyes are doing.     

REM sleep deprivation does not increase the sexual behaviors of male rats

Using several measures of sexual activity, 24 male and 30 female Sprague-Dawley rats were subjected to a pretreatment test and 3 posttests (immediate and Recovery Days 4 and 7) following REM sleep deprivation in a water tank. With careful controls, sexual activity was not significantly affected by the sleep treatments. Data do not support motivational hypotheses.     

Smooth pursuit eye movement and schizotypy in the community

Deficits in smooth pursuit eye movements are well documented in schizophrenia and schizotypic psychopathology. The status of eye tracking dysfunction (ETD) as an endophenotype for schizophrenia liability is relatively robust. However, the relation of ETD to schizophrenia-related deviance in the general population has not been confirmed. This study examined smooth pursuit eye tracking and schizotypal personality features in the general population. Smooth pursuit eye movement and schizotypal features were measured in 300 adult community subjects. The sample included both sexes, subjects with a wide age and educational range, and subjects with no prior history of psychosis. Primary outcome measures were peak gain (eye velocity/target velocity), catch-up saccade rate, and schizotypal feature scores. Total schizotypal features were significantly associated with decreased peak gain and were associated at the trend level with increased catch-up saccade rate. These associations were essentially unchanged after controlling for age, sex, and intellectual level effects. These data confirm a hypothesized association between schizotypal features and poorer eye tracking performance (principally, peak gain) in the general population as well as support the conceptualization of ETD as an endophenotype for schizophrenia liability.     

An investigation of the relationship between eye and retinal image movement in the perception of movement

The question investigated was whether or not eye movements accompanied by abnormal retinal image movements, movements that are either or both at a different rate or in a different direction than the eye movement, predictably lead to perceived movement. Os reported whether or not they saw a visual target move when the movement of the target was either dependent on and simultaneous with their eye movements or when the target movement was independent of their eye movements. In the main experiment, observations were made when the ratio between eye and target movement fem/tm) was 2/5, 1/5, 1/10, 1/20, and 0. All these ratios were tested when the direction of the target movement was in the same (H+), opposite (H?), and at right angles to (V+, V?) the movement of the eyes. Eye movements, target movements, and reports of target movement were recorded. Results indicate that a discrepancy between eye and target movement greater than 20% predictably leads to perceived target movement, whereas a discrepancy of 5% or less rarely leads to perceived movement. The results are interpreted as support for the operation of a compensatory mechanism during eye movements.