EEG spectral power in phasic and tonic REM sleep: different patterns in young adults and children.

Rapid eye movement sleep is composed of phasic and tonic periods, two distinguishable microstates in terms of arousal thresholds and sensory processing. Background electroencephalogram oscillations are also different between periods with (phasic state) and periods without (tonic state) eye movements. In Study 1, previous findings analysing electroencephalogram spectral power in phasic and tonic rapid eye movement sleep were replicated, and analyses extended to the high gamma range (52-90 Hz). In Study 2, phasic and tonic spectral power differences within a group of 4-8-year-old children were examined. Based on the polysomnographic data of 20 young adults, the phasic state yielded increased delta and theta power in anterior sites, as well as generally decreased high alpha and beta power in comparison to the tonic state. Moreover, phasic periods exhibited greater spectral power in the lower and the higher gamma band. Interestingly, children (n = 18) exhibited a different pattern, showing increased activity in the low alpha range during phasic periods. Moreover, during phasic in contrast to tonic rapid eye movement sleep, increased low and high gamma and enhanced low gamma band power emerged in anterior and posterior regions, respectively. The current findings show that spectral activity within the high gamma range substantially contributes to the differences between phasic and tonic rapid eye movement sleep, especially in adults. Moreover, the current data underscore the heterogeneity of rapid eye movement sleep, and point to marked differences between young adults and children regarding phasic/tonic electroencephalogram spectral power. These results suggest that the differentiation between phasic and tonic rapid eye movement periods undergoes maturation.

Objective and subjective components of the first-night effect in young nightmare sufferers and healthy participants.

The first-night effect--marked differences between the first- and the second-night sleep spent in a laboratory--is a widely known phenomenon that accounts for the common practice of excluding the first-night sleep from any polysomnographic analysis. The extent to which the first-night effect is present in a participant, as well as its duration (1 or more nights), might have diagnostic value and should account for different protocols used for distinct patient groups. This study investigated the first-night effect on nightmare sufferers (NM; N = 12) and healthy controls (N = 15) using both objective (2-night-long polysomnography) and subjective (Groningen Sleep Quality Scale for the 2 nights spent in the laboratory and 1 regular night spent at home) methods. Differences were found in both the objective (sleep efficiency, wakefulness after sleep onset, sleep latency, Stage-1 duration, Stage-2 duration, slow-wave sleep duration, and REM duration) and subjective (self-rating) variables between the 2 nights and the 2 groups, with a more pronounced first-night effect in the case of the NM group. Furthermore, subjective sleep quality was strongly related to polysomnographic variables and did not differ among 1 regular night spent at home and the second night spent in the laboratory. The importance of these results is discussed from a diagnostic point of view.

The interrelated effect of sleep and learning in dogs (Canis familiaris); an EEG and behavioural study.

The active role of sleep in memory consolidation is still debated, and due to a large between-species variation, the investigation of a wide range of different animal species (besides humans and laboratory rodents) is necessary. The present study applied a fully non-invasive methodology to study sleep and memory in domestic dogs, a species proven to be a good model of human awake behaviours. Polysomnography recordings performed following a command learning task provide evidence that learning has an effect on dogs' sleep EEG spectrum. Furthermore, spectral features of the EEG were related to post-sleep performance improvement. Testing an additional group of dogs in the command learning task revealed that sleep or awake activity during the retention interval has both short- and long-term effects. This is the first evidence to show that dogs' human-analogue social learning skills might be related to sleep-dependent memory consolidation.

Sleep spindles and intelligence in early childhood-developmental and trait-dependent aspects.

Sleep spindles act as a powerful marker of individual differences in cognitive ability. Sleep spindle parameters correlate with both age-related changes in cognitive abilities and with the age-independent concept of IQ. While some studies have specifically demonstrated the relationship between sleep spindles and intelligence in young children, our previous work in older subjects revealed sex differences in the sleep spindle correlates of IQ, which was never investigated in small children before. We investigated the relationship between age, Raven Colored Progressive Matrices (CPM) scores and sleep spindles in 28 young children (age 4-8 years, 15 girls). We specifically investigated sex differences in the psychometric correlates of sleep spindles. We also aimed to separate the correlates of sleep spindles that are because of age-related maturation from other effects that reflect an age-independent relationship between sleep spindles and general intelligence. Our results revealed a modest positive correlation between fast spindle amplitude and age. Raven CPM scores positively correlated with both slow and fast spindle amplitude, but this effect remained a tendency in males and vanished after correcting for the effects of age. Age-corrected correlations between Raven CPM scores and both slow and fast spindle amplitude were only significant in females. Overall, our results show that in male children sleep spindles are a maturational marker, but in female children they indicate trait-like intelligence, in line with previous studies in adolescent and adult subjects. Thalamocortical white matter connectivity may be the underlying mechanism behind both higher spindle amplitude and higher intelligence in female, but not male subjects. (PsycINFO Database Record

Content analysis of 4 to 8 year-old children's dream reports.

The role of dreaming in childhood and in adulthood are still equally enigmatic fields yet to be fully explored. However, while there is a consensus at least about the typical content and formal characteristics of adult dream reports, these features are still a matter of debate in the case of young children. Longitudinal developmental laboratory studies concluded that preschoolers' dreams usually depict static images about mostly animals and body states of the dreamer but they basically lack the active representation of the self, human characters, social interactions, dream emotions and motion imagery. Due to methodological arguments these results became the reference points in the literature of developmental dream research, in spite of the significantly different results of numerous recent and relevant studies using extra-laboratory settings. This study aims to establish a methodologically well-controlled and valid way to collect children's dreams for a representative period of time in a familiar home setting to serve as a comparison to the laboratory method. Pre trained parents acted as interviewers in the course of a 6 week-period of dream collection upon morning awakenings. Our results suggest that even preschoolers are likely to represent their own self in an active role (70%) in their mostly kinematic (82%) dream narratives. Their dream reports contain more human, than animal characters (70 and 7% of all dream characters respectively), and social interactions, self-initiated actions, and emotions are usual part of these dreams. These results are rather similar to those of recent extra-laboratory studies, suggesting that methodological issues may strongly interfere with research outcomes especially in the case of preschoolers' dream narratives. We suggest that nighttime awakenings in the laboratory setting could be crucial in understanding the contradictory results of dream studies in case of young children.

Ontogeny of dreaming: a review of empirical studies.

The examination of children's sleep-related mental experiences presents many significant challenges for researchers investigating the developmental trajectories of human dreaming. In contrast to the well-explored developmental patterns of human sleep, data from dream research are strikingly divergent with highly ambiguous results and conclusions, even though there is plenty of indirect evidence suggesting parallel patterns of development between neural maturation and dreaming. Thus results from studies of children's dreaming are of essential importance not only to enlighten us on the nature and role of dreaming but to also add to our knowledge of consciousness and cognitive and emotional development. This review summarizes research results related to the ontogeny of dreaming: we critically reconsider the field, systematically compare the findings based on different methodologies, and highlight the advantages and disadvantages of methods, arguing in favor of methodological pluralism. Since most contradictory results emerge in connection with descriptive as well as content related characteristics of young children's dreams, we emphasize the importance of carefully selected dream collection methods. In contrast nightmare-related studies yield surprisingly convergent results, thus providing strong basis for inferences about the connections between dreaming and cognitive emotional functioning. Potential directions for dream research are discussed, aiming to explore the as yet unraveled correlations between the maturation of neural organization, sleep architecture and dreaming patterns.

Development of a non-invasive polysomnography technique for dogs (Canis familiaris).

Recently dogs (Canis familiaris) have been demonstrated to be a promising model species for studying human behavior as they have adapted to the human niche and developed human-like socio-cognitive skills. Research on dog behavior, however, has so far almost exclusively focused on awake functioning. Here we present a self-developed non-invasive canine polysomnography method that can easily be applied to naive pet dogs. N=22 adult pet dogs (with their owners present) and N=12 adult humans participated in Study I. From these subjects, N=7 dogs returned on two more occasions for Study II. In Study I, we give a descriptive analysis of the sleep electroencephalogram of the dog and compare it to human data. In order to validate our canine polysomnography method in Study II, we compare the sleep macrostructure and the EEG spectrum of dogs after a behaviorally active day without sleep versus passive day with sleep. In Study I, we found that dogs' sleep EEG resembled that of human subjects and was generally in accordance with previous literature using invasive technology. In Study II, we show that similarly to previous results on humans daytime load of novel experiences and sleep deprivation affects the macrostructural and spectral aspects of subsequent sleep. Our results validate the family dog as a model species for studying the effects of pre-sleep activities on the EEG pattern under natural conditions and, thus, broaden the perspectives of the rapidly growing fields of canine cognition and sleep research.

Assistance dogs provide a useful behavioral model to enrich communicative skills of assistance robots.

These studies are part of a project aiming to reveal relevant aspects of human-dog interactions, which could serve as a model to design successful human-robot interactions. Presently there are no successfully commercialized assistance robots, however, assistance dogs work efficiently as partners for persons with disabilities. In Study 1, we analyzed the cooperation of 32 assistance dog-owner dyads performing a carrying task. We revealed typical behavior sequences and also differences depending on the dyads' experiences and on whether the owner was a wheelchair user. In Study 2, we investigated dogs' responses to unforeseen difficulties during a retrieving task in two contexts. Dogs displayed specific communicative and displacement behaviors, and a strong commitment to execute the insoluble task. Questionnaire data from Study 3 confirmed that these behaviors could successfully attenuate owners' disappointment. Although owners anticipated the technical competence of future assistance robots to be moderate/high, they could not imagine robots as emotional companions, which negatively affected their acceptance ratings of future robotic assistants. We propose that assistance dogs' cooperative behaviors and problem solving strategies should inspire the development of the relevant functions and social behaviors of assistance robots with limited manual and verbal skills.