A cognitive model of insomnia.

Sleep researchers in different disciplines disagree about how fully dreaming can be explained in terms of brain physiology. Debate has focused on whether REM sleep dreaming is qualitatively different from nonREM (NREM) sleep and waking. A review of psychophysiological studies shows clear quantitative differences between REM and NREM mentation and between REM and waking mentation. Recent neuroimaging and neurophysiological studies also differentiate REM, NREM, and waking in features with phenomenological implications. Both evidence and theory suggest that there are isomorphisms between the phenomenology and the physiology of dreams. We present a three-dimensional model with specific examples from normally and abnormally changing conscious states.

/pdf/dreaming-and-the-brain-toward-a-cognitive-neuroscience-of-4pu7cg288c.pdf

Dreaming and the brain: toward a cognitive neuroscience of conscious states

Study Objectives: This study examined effects on adolescent sleep patterns, sleepiness, and circadian phase of a school transition requiring an earlier start. Design and Setting: Adolescents were evaluated in 9th and 10th grades; school start time in 9th grade was 0825 and in 10th grade was 0720. Assessments at each point included 2 weeks of actigraphy and sleep diaries at home, followed by a 22-hour laboratory evaluation, including evening saliva samples every 30 minutes in dim light for determination of dim-light salivary melatonin onset phase (DLSMO), overnight sleep monitoring, and multiple sleep latency test (MSLT). Participants: Twenty-five females and 15 males, ages 14 to 16.2 were enrolled; 32 completed the study in 9th grade and 26 completed in 10th grade. Interventions: Participants kept their own schedules, except that laboratory nights were scheduled based upon school-night sleep pattems. Measurements and Results: According to actigraphy, students woke earlier on school days in 10th than in 9th grade, but they did not go to sleep earlier and they slept less. DLSMO phase was later in 10th grade (mean = 2102) than 9th grade (mean = 2024). Sleep latency on MSLT overall was shorter in 10th (mean = 8.5 minutes) than in 9th (mean = 11. 4 minutes), particularly on the first test of the moming at 0830 (5.1 vs 10.9 minutes). Two REM episodes on MSLT occurred in 16% of participants in 10th grade; one REM episode occurred in 48%. When those with REM sleep on one or both morning MSLTs (n=11) were compared to those without morning REM, significant differences included shorter sleep latency on the first test, less slow wave sleep the night before, and later DLSMO phase in those who had morning REM. Conclusions: Early start time was associated with significant sleep deprivation and daytime sleepiness. The occurrence of REM sleep on MSLT indicates that clinicians should exercise caution in interpreting MSLT REM sleep in adolescents evaluated on their usual schedules. Psychosocial influences and changes in bioregulatory systems controlling sleep may limit teenagers' capacities to make adequate adjustments to an early school schedule.

/pdf/adolescent-sleep-patterns-circadian-timing-and-sleepiness-at-4xcqeisral.pdf

Adolescent Sleep Patterns, Circadian Timing, and Sleepiness at a Transition to Early School Days

Maintenance of wakefulness test: A polysomnographic technique for evaluating treatment efficacy in patients with excessive somnolence ☆

Several theories claim that dreaming is a random by-product of REM sleep physiology and that it does not serve any natural function. Phenomenal dream content, however, is not as disorganized as such views imply. The form and content of dreams is not random but organized and selective: during dreaming, the brain constructs a complex model of the world in which certain types of elements, when compared to waking life, are underrepresented whereas others are over represented. Furthermore, dream content is consistently and powerfully modulated by certain types of waking experiences. On the basis of this evidence, I put forward the hypothesis that the biological function of dreaming is to simulate threatening events, and to rehearse threat perception and threat avoidance. To evaluate this hypothesis, we need to consider the original evolutionary context of dreaming and the possible traces it has left in the dream content of the present human population. In the ancestral environment human life was short and full of threats. Any behavioral advantage in dealing with highly dangerous events would have increased the probability of reproductive success. A dream-production mechanism that tends to select threatening waking events and simulate them over and over again in various combinations would have been valuable for the development and maintenance of threat-avoidance skills. Empirical evidence from normative dream content, children's dreams, recurrent dreams, nightmares, post traumatic dreams, and the dreams of hunter-gatherers indicates that our dream-production mechanisms are in fact specialized in the simulation of threatening events, and thus provides support to the threat simulation hypothesis of the function of dreaming.

https://www.unil.ch/files/live/sites/ln/files/shared/Revonsuo_1.pdf

Richard Park

Papers

REM sleep episodes during the multiple sleep latency test in narcoleptic patients