Variable-interval reinforcement schedule value influences responding following REM sleep deprivation

The effects of rapid-eye movement sleep deprivation (REMSD) in rats were studied in relation to variable-interval (VI) reinforcement schedule value. Initially, lever pressing was maintained on a VI 30-s schedule of food pellet delivery. After a baseline was established, rats were repeatedly exposed to 96 hr of REMSD and control conditions of an equivalent duration. Responding decreased following REMSD but not after exposure to control conditions. Lever pressing was then maintained on a VI 15-s schedule of food pellet delivery and exposure to the REMSD and control conditions was repeated. Under this condition following repeated REMSD exposures, rates of lever pressing became similar to baseline responding. A VI 30-s schedule of food pellet delivery was then reinstated and REMSD and control conditions were repeated. Lever pressing following exposure to the REMSD condition decreased for 3 of 4 rats. Results suggest that VI schedule value influences the effects of REMSD on responding.     

Necker cube and autokinetic illusions after awakening from REM and NONREM sleep: lack of effect.

Earlier studies demonstrated differential perceptions of the visual illusions, beta movements and spiral aftereffect, following awakening from REM and NONREM sleep. The present study tested the effects of awakening from the two phases of sleep on two additional visual illusions, the Necker cube and autokinetic illusions. 12 young adults were wakened from REM and NONREM sleep and tested on both illusions for three 1-min. trials, within 1 to 2 min. of the awakening. Comparison of the post-REM and post-NONREM illusions indicated a nonsignificant difference between the two waking conditions in the passive spontaneous reversal rates of the Necker cube. Data for the autokinetic illusion were not reported as they were unreliable.     

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.     

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 borderlands of waking: Quantifying the transition from reflective thought to hallucination in sleep onset

We lose waking consciousness spontaneously and regularly over the circadian cycle. It seems that every time we fall asleep, reflective thinking gradually gives way to our interactions with an imaginary, hallucinatory world that brings multimodal experiences in the absence of adequate external stimuli. The present study investigates this transition, proposing a new measure of hallucinatory states. Reflective thinking and motor imagery were quantified in 150 mentation reports provided by 16 participants after forced awakenings from different physiology-monitored time intervals after sleep onset. Cognitive agency analysis and motor agency analysis – which are objective (grammatical–semantic) tools derived from linguistic theories – show (i) a decrease in reflective thinking which sleepers would need to acknowledge the hallucinatory quality of their state, and (ii) an increase in motor imagery, indicating interactions with a hallucinatory world. By mapping these spontaneous changes in human consciousness onto physiology, we can in the long run explore the conditions of its decline, and possibilities for treatment.     

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.     

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.     

Differential effects of pentobarbital and cocaine on punished and nonpunished responding.

Similar rates of punished and nonpunished responding, maintained with equated rates of reinforcement, were established in pairs of rats. One subject of each pair was exposed to a random-ratio schedule of food presentation. The interreinforcement intervals for this subject comprised the intervals of a random-interval schedule of reinforcement for the other (yoked) rat. The random-ratio schedule maintained rates of responding higher than those maintained by the same rate of reinforcement schedule according to the yoked random-interval contingency. A random-ratio schedule of electric foot shock added to the random-ratio schedule of food presentation suppressed rates of responding such that similar rates of responding were observed in rats of both groups. Pentobarbital (3.0 to 17.0 mg/kg) increased punished responding at doses that had little effect on or decreased nonpunished responding, whereas cocaine (5.6 to 30 mg/kg) increased nonpunished responding at doses that decreased or did not alter punished responding. Qualitatively different effects of pharmacological agents on punished and nonpunished responding can be obtained using procedures that generate similar rates and temporal patterns of punished and nonpunished responding. The effects of pentobarbital and cocaine on responding can be determined by factors other than simply the baseline rate of responding.     

Memory performance after arousal from different sleep stages.

Learning material was presented to independent groups of subjects either after arousal from non-Rapid Eye Movement (non-REM) sleep, after arousal from REM sleep, or under conditions of no prior sleep. Measures of immediate and subsequent free recall were taken. Memory performance was found to be impaired where learning took place after non-REM arousal. This was manifest in the number of categories recalled, over both immediate and subsequent recall, and in the number of items recalled per category over subsequent recall. It was suggested that the memory performance decrement after non-REM arousal may be understood in terms of a retrieval deficit as well as a coding deficit. It is possible that the former is consequent upon a lower general level of arousal, whereas the latter is specific to memory.     

Poor recall of eye-movement signals from Stage 2 compared to REM sleep: implications for models of dreaming

An ongoing assumption made by sleep researchers is that since dreams are more often recalled on awakening from rapid eye movement (REM) sleep, dreams must occur more often during this stage of sleep. An alternative hypothesis is that cognition occurs throughout sleep, but the recall of this mentation differs on awakening. When a dream is not reported on awakening, there is no method of establishing whether it did not happen or was forgotten. The aim of the present study was to investigate this issue using an eye movement (EM) signal verification technique. Participants were instructed to produce an EM signal whenever they heard a tone. Tones were presented at increasing volume during Stage 2 and REM sleep until EM signal verification was observed. Ninety seconds after signal verification, participants were awakened and asked if they remembered hearing the tone or responding with the EM signal. Such recollection of signal verified tone (SVT) presentations was significantly less after Stage 2 sleep (65%) compared to REM sleep (100%) presentations. Furthermore, SVT recall was significantly correlated with reported dream recall frequency, suggesting the same processes involved in recalling SVTs might also underlie dream recall.     

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.     

Hemispheric lateralization of the EEG during wakefulness and REM sleep in young healthy adults

EEG recordings confirm hemispheric lateralization of brain activity during cognitive tasks. The aim of the present study was to investigate spontaneous EEG lateralization under two conditions, waking and REM sleep. Bilateral monopolar EEG was recorded in eight participants using a 12-electrode montage, before the night (5 min eyes closed) and during REM sleep. Spectral analysis (0.75-19.75 Hz) revealed left prefrontal lateralization on total spectrum amplitude power and right occipital lateralization in Delta activity during waking. In contrast, during REM sleep, right frontal lateralization in Theta and Beta activities and right lateralization in occipital Delta activity was observed. These results suggest that spontaneous EEG activities generated during waking and REM sleep are supported in part by a common thalamo-cortical neural network (right occipital Delta dominance) while additional, possibly neuro-cognitive factors modulate waking left prefrontal dominance and REM sleep right frontal dominance.