Waking and dreaming consciousness: neurobiological and functional considerations.

This paper presents a theoretical review of rapid eye movement sleep with a special focus on pontine-geniculate-occipital waves and what they might tell us about the functional anatomy of sleep and consciousness. In particular, we review established ideas about the nature and purpose of sleep in terms of protoconsciousness and free energy minimization. By combining these theoretical perspectives, we discover answers to some fundamental questions about sleep: for example, why is homeothermy suspended during sleep? Why is sleep necessary? Why are we not surprised by our dreams? What is the role of synaptic regression in sleep? The imperatives for sleep that emerge also allow us to speculate about the functional role of PGO waves and make some empirical predictions that can, in principle, be tested using recent advances in the modeling of electrophysiological data.

Odour, covering and ventilation.

A technique is described based on the decay in concentration of added SF(6) to measure L(0), the rate of leakage from an enclosure with no extraction of air. It is believed this measurement is much more precise than measurements of E(0), the minimum rate of extraction which just prevents leakage. Three out of four enclosures studied had L(0) values equating to residence times of air that were well under one hour. Relationships were developed between extraction rate and concentration and emission rate for enclosed odour sources based on mass transfer from water to air. These could be used to assess the benefits of minimising extraction rates while remaining within concentration limits set on the grounds of corrosion or toxicity. From these relationships a critical flow can be identified, termed Q(50), at which both the emission rate and concentration of a particular species are at 50% of their maximum value. In any particular system, Q50 for one species, such as H(2)S, will in general not be the same as for another species, nor for odour concentration. As a consequence the benefit of reducing extraction rates based on H(2)S may not appear as good as it would based on an assessment of odour concentration. A second consequence is that as the rate of air extraction is varied, the ratio between two species or between H(2)S and odour concentration, is likely to vary.

Preoperative anxiety and postoperative satisfaction in women undergoing elective caesarean section.

BACKGROUND: The primary aim was to investigate whether preoperative anxiety in women undergoing elective caesarean section predicts postoperative maternal satisfaction with the process, perceptions of recovery, analgesic use or length of hospital stay. Other factors that might influence postoperative satisfaction were also explored. METHOD: In 85 women awaiting elective caesarean section, anxiety, social support and aspects of preparation were measured in the 24 hours preceding surgery. Maternal satisfaction and perceptions of recovery were assessed around the third postoperative day. Satisfaction with the preoperative information from the anaesthetist and postoperative pain relief were also measured at this time. Medical notes were used to gather information on analgesia use and length of hospital stay. RESULTS: Preoperative anxiety scores were comparable with those of general surgical/medical patients. Preoperative trait anxiety and state anxiety were inversely associated with postoperative maternal satisfaction. State anxiety was also inversely associated with better recovery. Preoperative anxiety was not associated with analgesic use or length of hospital stay. Linear regression analysis indicated the degree of satisfaction with information from the anaesthetist and perceived emotional support from the partner explained 52% of the variance in postoperative maternal satisfaction. CONCLUSION: Lower preoperative anxiety is associated with greater maternal satisfaction with elective caesarean section and better recovery. Information provided by anaesthetists and perceived emotional support are also of importance. It may be possible to identify women with high anxiety and facilitate satisfaction and recovery through providing additional supportive input.

Sleep, learning, and dreams: off-line memory reprocessing.

Converging evidence and new research methodologies from across the neurosciences permit the neuroscientific study of the role of sleep in off-line memory reprocessing, as well as the nature and function of dreaming. Evidence supports a role for sleep in the consolidation of an array of learning and memory tasks. In addition, new methodologies allow the experimental manipulation of dream content at sleep onset, permitting an objective and scientific study of this dream formation and a renewed search for the possible functions of dreaming and the biological processes subserving it.

Effects of fluvoxamine and paroxetine on sleep structure in normal subjects: a home-based Nightcap evaluation during drug administration and withdrawal.

BACKGROUND: Acute and chronic administration of the selective serotonin reuptake inhibitors (SSRIs) have been widely reported to disrupt sleep in laboratory studies. This study examines the naturalistic, longitudinal effects of paroxetine and fluvoxamine on sleep quality in the home setting. METHOD: Fourteen healthy volunteers free of medical and neuropsychiatric symptoms entered a 31-day protocol: 7 days of drug-free baseline (days 1-7), 19 days of drug treatment (steady state during days 18-26), and 5 days of acute withdrawal (days 27-31). On day 8, the subjects were randomly assigned to receive either 100 mg/day of fluvoxamine or 20 mg/day of paroxetine (half receiving each drug) in divided morning and evening oral doses. Investigators remained blinded to drug assignment until all sleep data had been analyzed. Sleep was monitored using the Nightcap ambulatory sleep monitor. Four standard and 3 novel measures were computed and compared using multivariate analysis of variance, analysis of variance, and Bonferroni-corrected comparison of means. RESULTS: Sleep disruption was most clearly demonstrated using the novel measures eyelid quiescence index, rhythmicity, and eyelid movements per minute in non-rapid eye movement sleep, but was also apparent as determined by standard measures of sleep efficiency, number of awakenings, and sleep onset latency. Paroxetine disrupted sleep more than fluvoxamine, and paroxetine-induced sleep disruption persisted into the withdrawal phase. Rapid eye movement sleep was suppressed during treatment (especially for fluvoxamine) and rebounded during withdrawal (especially for paroxetine). CONCLUSION: We confirm laboratory polysomnographic findings of SSRI-induced sleep quality changes and demonstrate the Nightcap's efficacy as an inexpensive longitudinal monitor for objective sleep changes induced by psychotropic medication.

SSRI treatment suppresses dream recall frequency but increases subjective dream intensity in normal subjects.

Clinical lore and a small number of published studies report that the selective serotonin reuptake inhibitors (SSRIs) intensify dreaming. This study examines the dream effects of paroxetine and fluvoxamine in order to both increase clinical knowledge of these agents and to test an important potential method for probing the relationship between REM sleep neurobiology and dreaming in humans. Fourteen normal, paid volunteers (4 males, 10 females; mean age 27.4 year, range 22--39) free of medical or neuropsychiatric symptoms as well as of psychotropic or sleep affecting drugs completed a 31-day home-based study consisting of: 7 days drug-free baseline; 19 days on either 100 mg fluvoxamine (7 Ss) or 20 mg paroxetine (7 Ss) in divided morning and evening doses; and 5 days acute discontinuation. Upon awakening, subjects wrote dream reports, self-scored specific emotions in their reports and rated seven general dream characteristics using 5-point Likert scales. Dream reports were independently scored for bizarreness, movement and number of visual nouns by three judges. REM sleep-related measures were obtained using the Nightcap ambulatory sleep monitor. Mean dream recall frequency decreased during treatment compared with baseline. Dream report length and judge-rated bizarreness were greater during acute discontinuation compared with both baseline and treatment and this effect was a result of the fluvoxamine-treated subjects. The subjective intensity of dreaming increased during both treatment and acute discontinuation compared with baseline. Propensity to enter REM sleep was decreased during treatment compared with baseline and acute discontinuation and the intensity of REM sleep increased during acute discontinuation compared with baseline and treatment. The decrease in dream frequency during SSRI treatment may reflect serotonergic REM suppression while the augmented report length and bizarreness during acute SSRI discontinuation may reflect cholinergic rebound from serotonergic suppression.

Brain-mind states: reciprocal variation in thoughts and hallucinations.

The exclusion of thinking from recent studies of sleep mentation has hindered a full appreciation of how cognitive activity differs across the states of waking and sleep. To overcome this limitation, this study investigated thoughts and hallucinations using experience sampling, home-based sleep-wake monitoring, and formal analyses of the psychological data. The prevalence of thoughts decreased gradually from waking through sleep onset and non-REM sleep, to reach its nadir in REM sleep, whereas hallucinations increased sharply across these states. Furthermore, multiple occurrences of hallucinations but not of thoughts increased significantly from sleep onset through non-REM sleep, to a peak in REM sleep. This reciprocity in thoughts and hallucinations might reflect a progressive shift from high to low aminergic-to-cholinergic neuromodulatory ratios across wake-sleep states, accompanied by an array of changes in the regional activation patterns of the brain.

Brain-mind states: I. Longitudinal field study of sleep/wake factors influencing mentation report length.

STUDY OBJECTIVES: To collect and analyze reports of mental activity across sleep/wake states. DESIGN: Mentation reports were collected in a longitudinal design by combining our Nightcap sleep monitor with daytime experience sampling techniques. Reports were collected over 14 days and nights from active and quiet wake, after instrumental awakenings at sleep onset, and after both spontaneous and instrumental awakenings from REM and NREM sleep. SETTING: All reports were collected in the normal home, work and school environments of the subjects. PARTICIPANTS: Subjects included 8 male and 8 female undergraduate students (19-26 years of age). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: A total of 1,748 reports, averaging 109 per subject, were collected from active wake across the day (n=894), from quiet wake in the pre-sleep onset period (n=58), from sleep onset (n=280), and from later REM (n=269) and nonREM (n=247) awakenings. Median report lengths varied more than 2-fold, in the order REM > active wake > quiet wake > NREM = sleep onset. The extended protocol allowed many novel comparisons between conditions. In addition, while spontaneous REM reports were longer than those from forced awakenings, the difference was explained by the time within the REM period at which the awakenings occurred. Finally, intersubject differences in REM report lengths were correlated with similar differences in waking report lengths. CONCLUSIONS: The use of the Nightcap sleep monitoring system along with waking experience sampling permits a more complete sampling and analysis of mental activity across the sleep/wake cycle than has been previously possible.

The mind in REM sleep: reports of emotional experience.

STUDY OBJECTIVES: No consensus has been reached on the characteristics of emotional experience during rapid eye movement sleep (REM). Thus, the relationship between the emotional brain activation and mental activity in REM remains unclear. Our objective is to characterize emotional experience in REM in order to facilitate understanding of brain-mind correlations in this state. DESIGN: We combined instrumental awakenings from REM with the subjects' own ratings of the occurrence and intensity of discrete emotion types for each line in their REM mentation reports. SETTING: The study was performed in the subjects' own homes over three consecutive nights using ambulatory polysomnography. PARTICIPANTS: Nine normal healthy subjects, age 31-60 (mean=43.0). INTERVENTIONS: Awakenings 5-15 minutes into REM periods across the night. MEASUREMENTS AND RESULTS: Emotions were found in 74% of 88 mentation reports, with a balanced proportion of positive and negative emotions. Among the reports scored for emotions, 14% contained one emotion and 86% contained two or more different emotion types. Joy/elation was the most frequent emotion, found in 36% of the reports, followed by surprise (24%), anger (17%), anxiety/fear (11%), and sadness (10%). Anxiety/fear was significantly less intense than joy/elation, anger, and surprise. Except for surprise, no specific emotion type changed from the first to the second half of the night. Negative emotions and surprise but not positive emotions varied significantly across subjects. CONCLUSIONS: The analysis of subject reports of emotions following instrumental awakenings demonstrate a balanced and widespread occurrence of both positive and negative emotions in REM sleep dreams. Emotions in REM are likely to be powerfully modulated by the neurobiological processes which differentiate REM from waking.