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BACKGROUND Modulation of behavior and physiology by dietary perturbations early in life can provide clues to the pathogenesis of adult diseases. We tested the hypothesis that a period of early protein supplementation modulates sympathetic nervous system activity demonstrated indirectly by an increase in active sleep state distribution in very low birth weight (VLBW) infants. METHODS VLBW infants (n = 71) were randomized to a total parenteral nutritional regimen providing 18% of the energy intake as amino acids (AA) or a conventional regimen providing 12.5% to achieve targeted AA intakes of 4 g/kg/day (0.004 kcal/kg/day) and 3 g/kg/day (0.003 kcal/kg/day), respectively. Both groups were weaned to enteral feeding and advanced to provide similar AA intake of 4 g/kg/day (0.004 kcal/kg/day). Six-hour daytime, behavioral sleep studies were performed when the infants reached full enteral intake (165 ml/kg/day). RESULTS Infants in the high protein group spent more time in active sleep (77.2 ± 10.5% vs. 70.7 ± 11.8%), p

SummaryIn humans and other mammals, the stillness of sleep is punctuated by bursts of rapid eye movements (REMs) and myoclonic twitches of the limbs [1]. Contrary to the notion that twitches are mere by-products of dreams, sensory feedback arising from twitching limbs provides a rich and unique source of activation to the developing sensorimotor system [2]. In fact, it is partly because of the behavioral activation of REM sleep that this state is also called active sleep (AS), in contrast with the behavioral quiescence that gives quiet sleep (QS)—the second major stage of sleep—its name. In human infants, for which AS occupies eight or more hours of each day [3], limb twitching is one among several components that help to identify the state [4-7]; nonetheless, we know relatively little about the structure and functions of twitching across development. Recently, in sleeping infants over the first seven postnatal months [8], we documented a pronounced shift in the temporal expression of twitching beginning around three months of age that suggested a qualitative shift in how twitches are produced. Here, we combine behavioral assessments of twitching with high-density electroencephalography (EEG) and demonstrate that this shift reflects the developmental emergence of limb twitches during QS. Twitches during QS are not only unaccompanied by REMs, but they also occur synchronously with sleep spindles, a hallmark of QS. As QS-related twitching increases with age, sleep spindle rate also increases along the sensorimotor strip. The emerging synchrony between subcortically generated twitches and cortical oscillations suggests the development of functional connectivity among distant sensorimotor structures, with potential implications for detecting and explaining atypical developmental trajectories.

Sleep is important for the development of preterm infants. During sleep, neural connections are formed and the development of brain regions is triggered. In general, various rudimentary sleep states can be identified in the preterm infant, namely active sleep (AS), quiet sleep (QS) and intermediate sleep (IS). As the infant develops, sleep states change in length and organization, with these changes as important indicators of brain development. As a result, several methods have been deployed to distinguish between the different preterm infant sleep states, among which polysomnography (PSG) is the most frequently used. However, this method is limited by the use of adhesive electrodes or patches that are attached to the body by numerous cables that can disturb sleep. Given the importance of sleep, this review explores more unobtrusive methods that can identify sleep states without disturbing the infant. To this end, after a brief introduction to preterm sleep states, an analysis of the physiological characteristics associated with the different sleep states is provided and various methods of measuring these physiological characteristics are explored. Finally, the advantages and disadvantages of each of these methods are evaluated and recommendations for neonatal sleep monitoring proposed.

Sleep architecture carries vital information about brain health across the lifespan. In particular, the ability to express distinct vigilance states is a key physiological marker of neurological wellbeing in the newborn infant although systems-level mechanisms remain elusive. Here, we demonstrate that the transition from quiet to active sleep in newborn infants is marked by a substantial reorganization of large-scale cortical activity and functional brain networks. This reorganization is attenuated in preterm infants and predicts visual performance at two years. We find a striking match between these empirical effects and a computational model of large-scale brain states which uncovers fundamental biophysical mechanisms not evident from inspection of the data. Active sleep is defined by reduced energy in a uniform mode of neural activity and increased energy in two more complex anteroposterior modes. Preterm-born infants show a deficit in this sleep-related reorganization of modal energy that carries novel prognostic information., Patterns of brain activity during sleep in early stages of life influence brain development and behavior. Here, the authors reveal cortical dynamics underpinning quiet and active sleep states in pre- and full-term infants, and their links to neurodevelopmental outcomes.

In this short review, I would like to share some personal memories about the insights and achievements of Michel Jouvet in the field of sleep ontogeny. The first time I met Michel Jouvet was in 1972 when he accepted to chair my thesis on sleep, the research work being preformed in Howard Roffwarg's lab in New York. From then on we had many discussions together about the mechanisms and nature of neonatal Paradoxical Sleep, notably its characteristic muscular "twitches". The idea emerged of a genetically programmed pattern of motor activation responsible for this state of "seismic" sleep. Such a pattern would underlie, for example, the facial mimics displayed during sleep in early life, whose function would be to "pre-practice" a specific behavior. Later on, in the 1980's Michel Jouvet had the masterful insight to extend this role of Paradoxical Sleep to the theory of genetic programming for maintaining psychological individualism. Michel Jouvet's scientific curiosity and generosity led to his exceptional accomplishments, and he will remain as an immense figure in the culture of sleep science.

Aim of this study was to investigate the preferential looking behaviour, subsequent to a familiarization task (8-min) with a previously responsive or motionless face, before and after a sleep cycle. Moreover, the role of the active sleep in memory consolidation of the responsive or motionless faces was explored. Hypotheses were that the newborns undergoing a motionless familiarization will exhibit a novelty effect (preference for the novel face) whereas the newborns undergoing a responsive familiarization will show a familiarity effect (preference for the known face) before and after the sleep cycle; moreover, the amount of active sleep will be associated with the looking time at the known face after a sleep cycle. Forty-five healthy full-term newborns were randomly assigned to two groups (group 1: motionless-familiarization and group 2: responsive-familiarization); in both groups newborns were video-recorded during four post-familiarization face-preference tasks, two of them performed before and two after a sleep cycle. During the pre-sleep-trials, there was not a significant preference for one face in both groups. During the post-sleep trials, the newborns showed a clear preference for the novel face. This effect was more evident in group 1. Only in group 2 there was a significant positive correlation between the active sleep duration and the looking duration at the known-face during the post-sleep trials (r=0.41; p=0.040). Multiple regression confirmed that only in the group 2 the total duration of the active sleep was associated with the looking duration at the known-face during the post-sleep trials (Adjusted R2=0.13; β=0.41; t=2.2; p=0.040). Findings showed that in newborns the face representation can be recalled after a sleep cycle. Moreover, the amount of the active sleep predicted the post-sleep looking toward the known-face only in the newborns who interactively familiarized with the face.

Sleep, the brain and the ability to interact with the environment change a great deal over the first year of life; however, there are no studies on the possible influence of different environmental stimulations on the organization of subsequent sleep–wake cycles in infants. The hypothesis of this study was that greater continuity of contingent tactile stimulation decreases crying behavior, subsequent active sleep (AS) and its fragmentation, and increases smiling behavior and subsequent quiet sleep in newborns. Forty out of the 82 newborns (15- to 30-hr old) of the initial sample satisfied the inclusion criteria and completed the first cycle of sleep during the period between two feedings. The 40 newborns were randomly assigned to four groups after 2′ of baseline observation: continuous stimulation (CS, n = 10); discontinuous nonperiodic stimulation (DnPS, n = 10); discontinuous periodic stimulation (DPS, n = 10); absent stimulation (AbS, n = 10). During baseline measurements, there were no significant differences in crying and smiling behaviors between the four groups, while during the subsequent stimulated wake, the CS group compared to the DnPS group showed more smiling (p

Objective It has been reported that pacifiers might reduce the risk of SIDS by favouring infants’ arousability from sleep. We evaluated the influence of a pacifier on the frequency and duration of spontaneous arousals in healthy infants. Methods Polygraphic recordings were performed in 14 infants with an age of 51.7 ± 19.9 days (means ± SD) who regularly used a pacifier during sleep. Cortical and subcortical arousals were scored according to the recommendations of the “International Paediatric Work Group on Arousals.” The number of arousals per 10-min-period and the duration of arousals were determined for periods of pacifier use as well as for periods after pacifier dislodgement and were compared with the data of 10 control infants (age 49.8 ± 16.5 days) who never used a pacifier. Results Altogether, 211 arousals in pacifier users and 225 arousals in non-users were scored. In pacifier users, 2.0 ± 1.6 arousals per 10-min-period with a duration of 12.2 ± 3.0 s occurred during pacifier use, and 1.7 ± 1.6 arousals per 10-min-period with a duration of 12.2 ± 3.1 s occurred during periods without pacifier. In pacifier non-users, 2.3 ± 1.2 arousals per 10-min-period (duration 13.9 ± 2.9 s) were scored. The results did not show a significant difference concerning frequency and duration of spontaneous arousals between pacifier users and non-users. Conclusions Our findings suggest that factors other than arousal mechanisms might be responsible for the efficacy of pacifiers in SIDS prophylaxis.

SUMMARY The cyclic patterns of sleep and wakefulness (behavioural ‘states’) were studied polygraphically in a group of 21 normal newborn infants on the first and the fifth days of life. The percentage of time spent awake underwent drastic reduction between the first and the fifth days. The percentage of time spent in state 2 (active sleep) increased correspondingly. The percentage of time spent in state 1 (quiet sleep) remained relatively unchanged; it exceeded state 2 on the first day and was exceeded by state 2 on the fifth day. On the fifth day, there was a tendency for the number of state transitions per hour to be less than on the first day, and for the durations of periods in state 2 to increase. On the first day, infants quite often appeared to wake directly from state 1, but this seldom happened on the fifth day, when waking usually occurred from state 2. Late-clamped infants spent a higher percentage of time in state 1 and less in the quiet awake states than did the early-clamped infants. Individual differences between the lateclamped infants were much greater. Respiratory rate (which is positively related to blood volume in the neonate) was significantly lower in the early-clamped compared with the late-clamped group, in whom the results showed considerable scatter. It is possible that late clamping of the cord represents an additional stress to the neonate and that early clamping confers an advantage on the infant who spends more time awake on the first day, thereby promoting a sound mother and baby relationship. RESUME Un groupe de 21 nouveaux-nes normaux ont eteetudies au ler et 5eme jour de la naissance a l'aide de techniques polygraphiques pour mesurer le pourcentage de temps passe dans les differents etats de vigilance ainsi que la duree des periodes de chacun de ces etats. Le pourcentage de temps passeeveille subit une reduction considerable entre le ler et le 5eme jour. Le pourcentage de temps en stade 2 (sommeil actif) s'accroit d'autant. Le temps passe en stade 1 (sommeil tranquille) demeure inchange, de telle facon qu'il depasse le temps du stade 2 le premier jour et est inferieur le 5eme. Il y a une tendance au 5eme jour a ce que le nombre de changements d'etats par heure soit moindre et que les periodes individuelles de stade 2 s'allongent. Au ler jour, tres souvent, les enfants se reveillent directement a partir du stade 1, mais au 5eme jour, le reveil surveint generalement a partir du stade 2. Les nourrissons a‘clampage tardif’ passent un pourcentage plus eleve de temps au stade 1 et moindre a l'etat tranquille eveille que les enfants a‘clampage precoce’. Les enfants a clampage tardif presentent des variations individuelles beaucoup plus importantes. Le rythme respiratoire qui est relie plus au volume sanguin chez le nouveau-ne est significativement plus lent chez les nourrissons a clampage precocee qu'a clampage tardif, parmi ceux-ci, les resultats presentent une dispersion tres marquee. Il est possible que le clampage tardif du cordon represente une agression supplementaire chez le nouveau-ne et que la clampage precoce confere un avantage en permettant au nourrisson de passer plus de temps eveille le ler jour, ce qui favorise une bonne relation mere-enfant. ZUSAMMENFASSUNG Es wurde eine Gruppe von 21 normaler Neugeborener am 1. und 5. Lebenstag mit polygraphischen Methoden untersucht, um den Prozentsatz der Zeit, die in jedem der verschiedenen Verhaltenszustande verbracht wurde, und die Dauer der einzelnen in ihnen verbrachten Perioden zu messen. Der Zeitanteil des Wachseins erfuhr zwischen dem 1. und 5. Tage eine drastische Verminderung. Der Prozentsatz der Zeit, die im Stadium 2 (aktiven Schlaf) verbracht wurde, stieg entsprechend an. Die Gesamtdauer des Stadium 1 (ruhigen Schlafes) blieb relativ unverandert, so das er am ersten Tage uber den Anteil des Stadium 2 hinausging und am funften Tage hinter ihm zuruckblieb. Es zeigte sich die Tendenz, das die Zahl der Stadienwechsel pro Stunde am 5. Tage geringer war und die Dauer der einzelnen Perioden im Stadium 2 anstieg. Am 1. Lebenstag erwachten die Kindern offenbar ganz haufig direkt aus dem Stadium 1, wahrend sie am 5. Tage gewohnlich aus Stadium 2 erwachten. Die spatabgenabelten Kinder verbrachten einen groseren Prozentsatz ihrer Zeit im Stadium 1 und weniger im ruhigen Wachzustand als die fruabgenabelten Kinder. Die spatabgenabelten Kinder zeigten viel grosere individuelle Unterschiede. Die Atemfrequenz, die dem Blutvolumen beim Neugeborenen proportional ist, war bei den fruhabgenabelten Kindern signifikant niedriger als bei den spatabgenabelten, bei denen die Ergebnisse wiederum eine betrachtliche Schwankungsbreite zeigten. Es ist moglich. das das Spatabnabeln einen zusatzlichen Stress fur das Neugeborene bedeutet und das das Fruhabnabeln von Vorteil ist, da es das Kind am 1. Tage mehr Zeit im Wachzustand verbringen last, was eine intakte Mutter-Baby-Beziehung begunstigt.

SUMMARY Polygraphic methods were used to evaluate the percentage distribution of sleep and awake states and the mean duration of individual periods spent in these states in infants with Down's syndrome, bilirubinaemia and in a heterogeneous group of ‘high-risk’ infants. Not unexpectedly, alterations from previously established normal values were found, as were differences in pattern between the groups. Infants with Down's syndrome spend more time awake at the expense of time in state 2 (active sleep), but prolonged sleep cycles are occasionally possible. Bilirubinaemic infants showed a drastic reduction in the amount of time spent in the awake states. Individual periods spent in state 2 were significantly longer, producing also a prolonged sleep cycle duration. The high-risk group spent abnormally short periods in state 2 and none of the infants studied produced a long sleep cycle. The amount of time spent in awake states varied widely. Anti-epileptic drugs induced more and longer individual periods of state 1 (quiet sleep) at the expense of state 2. The pathophysiological mechanisms behind these alterations in the state cycle are discussed. RESUME Cycles de niveaux de vigilance chez les nouveaux-nes anormaux Grâce a des methodes polygraphiques, trois groupes de nourrissons de conditions anormales ont eteetudies pour evaluer le pourcentage de temps passe dans chacun des divers etats de sommeil et d'eveil ainsi que la duree des periodes individuelles passees dans ces differents etats. Comme on pouvait s'y attendre des differences ont ete observees non seulement par rapport aux valeurs etablies anterieurement mais aussi avec les trois groupes. Les mongoliens passent plus de temps eveilles aux depens du temps passe en stade 2 (sommeil actif), mais des cycles prolonges de sommeil ont pu etren otes occasionnellement. Les nourrissons hyperbilirubinemiques ont montre une reduction considerable du temps passe dans les etats de veille. Les periodes individuelles en stade 2 etaient significativement allongees et de ce fait, les plus longs cycles de sommeil etaient egalement allonges. Le groupe heterogene des nourrissons a `hauts risques' presentait des periodes anormalement courtes en stade 2 et en aucun cas, il n'a ete enregistre de longs cycles de sommeil. La quantite de temps passe en etat de veille variait considerablement. Les medications anti-epileptiques provoquaient un accroissement en nombre et en duree des periodes de stade 1 (sommeil tranquille) aux depens des periodes du stade 2. Les mecanismes physio-pathologiques sous jacents a ces alterations des cycles de vigilance sont discutes. ZUSAMMENFASSUNG Verhaltenszustandszyklen bei abnormen Neugeborenen Drei Gruppen von Kindern mit abnormen Bedingungen wurden mit polygraphischen Methoden untersucht, um den Prozentsatz der Zeit, die sie in jedem der verschiedenen Schlaf- und Wachzu-stande verbringen, und die Dauer der einzelnen Perioden dieser Zustande zu berechnen. Erwartungsgemas fanden sich Unterschiede nicht allein von fruher festgestellten Werten, sondern auch zwischen den drei Gruppen. Die Kinder mit Down-Syndrom verbrachten mehr Zeit im Wachzustand auf Kosten der Zeit des Stadium 2 (aktiven Schlafes), doch wurden gelegentlich auch verlangerte Schlafzyklen gefunden. Die Kinder mit Bilirubinaemie zeigten eine betrachtliche Verminderung der Zeitdauer, die im Wachzustand verbracht wurde. Einzelne Perioden im Schlafstadium 2 waren signifikant verlangert und als Ergebnis dessen war der langste Schlafzyklus auch verlangert. Die heterogene Gruppe der ‘high risk’ Kinder zeigte abnorm kurze Perioden im Schlafstadium 2, und in keinem Fall wurde ein langerer Schlafzyklus festgestellt. Die Zeitdauer des Wachzustandes variierte betrachtlich. Antiepileptische Medikamente verursachten grosere Mengen und langere Einzelperioden des Stadium 1 (vuhigen Schlafes) auf Kosten des Stadium 2. Die pathophysiologischen Mechanismen dieser Veranderungen im Zustandszyklus werden diskutiert.

Objective To further understand state development of preterm infants throughout hospitalization and the effects of selected infant characteristics on state development. Design Secondary data analysis of a 2-group, experimental design study. Setting Two nurseries in a Northwest medical center. Participants Ninety-seven hospitalized, medically stable, preterm infants. Fifty-one subjects were females. Methods Two hundred and eighty-five real-time video recordings of infants performed during 4 hour interfeeding intervals. Sleep-wake states were coded at 15 second intervals. Results Active sleep was the dominant state across postmenstrual ages. Although not statistically significant, preterm infants showed developmental changes in state organization with increased quiet sleep, drowsy, and awake, decreased active sleep, and more defined and less diffuse states over age. A significant gender effect was found, with males having less active sleep ( p =.012), more drowsy ( p =.03), more awake ( p =.043), less defined ( p =.002), and more diffuse ( p =.001) states compared with females. Conclusion The predominance of active sleep during the preterm period reflects level of brain maturation. The results emphasize individual variations in state organization influenced by endogenous and environmental factors. Gender differences are potential sources of individual variation.

Cardio Respiratory Coupling (CRC) plays a key role during infant development. Nonetheless, mechanisms underlying it are still mostly unexplained and tools to assess it are often inadequate to understand its functioning. This study aims to evaluate the feasibility of CRC activity detection and quantification analyzing ECG and respiration of newborn healthy subjects. Cross-spectral analysis (coherence) and a novel application of a nonlinear method (Bivariate Phase Rectified Signal Averaging) were applied on 10 minutes recording from 4 subjects. Our preliminary results show that these methods can provide significant information about the occurrence and the strength of CRC, opening interesting perspectives in the evaluation of cardiorespiratory pathologies in newborn infants. In particular, the observed dynamic behavior appears stable and centered around one single frequency in Quiet Sleep, while being more variable and less consistent in Active Sleep.

Yawning has been observed in foetuses and preterm infants. The aim of this study was to assess the frequency and the 24 h distribution of yawning in preterm infants. Twelve low-risk infants between 31 and 40 weeks of post-conceptional age (PCA) were continuously video-recorded for 24 h in their incubator. Spontaneous yawning was defined as opening of the mouth to its full extension in a dramatic stretch movement. The results showed that the rate of yawning across the 24-h period was 1.10/h. The highest incidence of yawns was in the waking motility pattern when compared to active sleep or quiet sleep motility patterns. Between 31 and 40 weeks, yawn incidence significantly decreased mainly during the day. The marked decrease in yawn frequency with age may be related to the development of circadian and homeostatic control of sleep and wake.

Background and purpose The aim of the present study was to verify whether the proposed method of computer-supported EEG analysis is able to differentiate the EEG activity in quiet sleep (QS) from that in active sleep (AS) in newborns. A quantitative description of the neonatal EEG may contribute to a more exact evaluation of the functional state of the brain, as well as to a refinement of diagnostics of brain dysfunction manifesting itself frequently as ‘dysrhythmia' or ‘dysmaturity'. Patients and methods Twenty-one healthy newborns (10 full-term and 11 pre-term) were examined polygraphically (EEG—eight channels, respiration, ECG, EOG and EMG) in the course of sleep. From each EEG record, two 5-min samples (one from QS and one from AS) were subject to an off-line computerized analysis. The obtained data were averaged with respect to the sleep state and to the conceptional age. The number of variables was reduced by means of factor analysis. Results All factors identified by factor analysis were highly significantly influenced by sleep states in both developmental periods. Likewise, a comparison of the measured variables between QS and AS revealed many statistically significant differences. The variables describing (a) the number and length of quasi-stationary segments, (b) voltage and (c) power in δ and θ bands contributed to the greatest degree to the differentiation of EEGs between both sleep states. Conclusion The presented method of the computerized EEG analysis which has good discriminative potential is adequately sensitive and describes the neonatal EEG with convenient accuracy.

The multichannel electroencephalograph (EEG) of six healthy term neonates was recorded during awake as well as during active and quiet sleep. The existence and nature of the interdependencies among the different brain areas were studied by means of a multivariate variant of the surrogate data method. Such interdependencies were then quantified by using the coherence function and a newly developed non-linear index. The results showed that during quiet sleep these interdependencies were mostly non-linear, asymmetric and greater than those found during both awake and active sleep. We conclude that the index might be useful to define patterns of EEG interdependencies in healthy neonates, thereby allowing the early detection of brain dysfunctions.

Although thermoregulation and sleep exhibit gender differences in adults, the question is still debated in neonates. The aim of this study was to examine the relationship between gender-related sleep differences and cool defence mechanisms in neonates. Sleep and thermoregulation were recorded in healthy preterm neonates (21 boys and 17 girls, 37 +/- 2 weeks post-conceptional age) exposed to thermoneutral and cool conditions. Sleep was analysed for continuity and structure. Although the cool exposure did not strongly impair body homeothermia, sleep was altered but without any significant gender difference. However, when data recorded under each of the thermal conditions were pooled, some gender differences emerged: boys slept less, with more wakefulness after sleep onset, more active sleep and less quiet sleep than girls. In contrast to sleep architecture, most of the sleep continuity parameters exhibited greater variability in boys than in girls. This variability may bias the statistical analyses and probably explains the varying conclusions reported in the literature regarding gender-specific sleep-related differences.

The responses of the thermoregulatory effectors vary greatly among neonates. Therefore, we assume that a small decrease in air temperature from thermoneutrality induces various thermoregulatory responses within neonates that represent an energy cost due to the cold defence processes. To determine the importance of this variability in nursing, 26 neonates were explored at thermoneutrality and in a cool environment (-1.5 degrees C from thermoneutrality) similar to that which occurs currently in clinical procedure. Oxygen consumption (VO2), oesophageal and skin temperatures, as well as sleep parameters were recorded continuously in both conditions. Analysis of all of the data from all of the neonates revealed that the cool exposure induced thermal and sleep disturbances, but VO2 did not increase and was not negatively correlated to body temperature (as might be expected). Analyses of individual data showed large variability in body temperature regulation: the neonates could be assigned to one of three groups according to the direction of the individual slopes of VO2 versus oesophageal or skin temperature. The groups also differed according to the sleep changes recorded in the cool condition. The results show that the definition of thermoneutrality should be revised by incorporating non only changes in the body temperature, but also the sleep disturbances (increased wakefulness and active sleep, decreased quiet sleep), which are criteria that are more sensitive to mild cool exposure. Thermoneutrality should be defined for each individual, since the results stress that the variability does not help to predict a general pattern of thermoregulatory responses in cool-exposed neonates.

1. Arousal from sleep is an important protective mechanism that is depressed by repeated episodes of hypoxia. We aimed to determine how rapidly arousal depression occurs during repeated hypoxia and to determine if the depression is sleep state specific. 2. Three successive 12 h overnight sleep recordings were performed in six newborn lambs instrumented to record sleep state, blood pressure, heart rate and blood gases. The first (control) and third (recovery) nights were baseline studies (inspired oxygen fraction, FI,O2 = 0.21) to determine the spontaneous arousal probability. During the second (test) study night, lambs were exposed to a 60 s episode of isocapnic hypoxia (FI,O2 = 0.10; inspired carbon dioxide fraction, FI,CO2 = 0.03) during every epoch of sleep. 3. During quiet sleep (QS), the probability of arousing to hypoxia (56%) remained significantly higher than the probability of arousing spontaneously (18%) throughout the repeated hypoxic exposures (chi(2) = 81.5, P < 0.001). By contrast, during active sleep (AS) arousal rapidly became depressed with repetition of the hypoxic stimulus; the probability of arousal in hypoxia (52%) was significantly higher than the probability of spontaneous arousal (12%) during the first ten hypoxic exposures (chi(2) = 18.2, P < 0.001), but there was no difference thereafter. 4. We conclude that, when repeated, moderate hypoxia very rapidly becomes ineffective as an arousing stimulus in AS, but not in QS. These results suggest that the arousal mechanism is particularly vulnerable to failure during AS.

We studied 142 preterm infants (mean gestation 31 weeks, mean birthweight 1364 g) fed prospectively varied protein and energy intakes. Infants were grouped as either slow or rapid growers based on rate of weight gain. Rapid growers had increased heart rates (166 vs 160 beats/min), respiratory rates (55.7 vs 53.9 bpm), energy expenditure (64.8 vs 61.6 kcal kg(-1) day(-1)), urinary C-peptide levels (1.59 vs 0.79 ng ml(-1)) and time in active sleep (78.0 vs 75.2%), and decreased spectral edge frequency in the electroencephalogram (2.96 vs 4.45 Hz) compared to slow growers. We conclude that preterm infants growing at varying rates manifest physiological and behavioral differences, and that these patterns may reflect altered autonomic balance.

In the present study, ongoing and evoked activity of antidromically identified trigemino–thalamic tract (TGT) neurons was examined over the sleep–wake cycle in cats. There was no difference in the mean spike discharge rate of TGT neurons when quiet sleep (QS) and active sleep (AS) were compared with wakefulness (W). However, tooth pulp-evoked responses of TGT neurons were decreased during AS when compared to W. Conversely, the responses of TGT neurons to air puff activation of facial hair mechanoreceptors reciprocally increased during AS when compared to W. The present data demonstrate that ascending sensory information emanating from distinct orofacial areas is differentially modified during the behavioral state of AS. Specifically, the results obtained suggest that during AS, sensory information arising from hair mechanoreceptors is enhanced, whereas information arising from tooth pulp afferents is suppressed. These data may provide functional evidence for an AS-related gate control mechanism of sensory outflow to higher brain centers.

Five physiologic groupings of 45 EEG-sleep measures were acquired from serial 24-channel EEG-sleep recordings (i.e., sleep architecture, continuity, EEG spectral, phasic, and autonomic measures), utilizing 129 studies on 56 healthy preterm infants from 28 to 43 weeks postconceptional age (PCA) who were neurodevelopmentally normal on follow-up. Regression analyses chose the least number of measures that best reflected maturation. Four of 45 variables (i.e., spectral alpha energy during quiet sleep, total spectral EEG energy, arousal number during active sleep, and percentage of EEG discontinuity) most significantly explained brain maturation in neonates36 weeks PCA. Three of 45 variables (i.e., spectral theta and beta energies during active sleep and spectral alpha energy during quiet sleep) were most representative after 36 weeks PCA. Spectral EEG energies were the strongest indicators of maturation compared with other measures, particularly in near-term neonates.

Many studies have investigated infant smiling behaviour during wake and active sleep. In the majority of studies authors agreed that two month-old infants exhibit social smiles. However it is not clear if newborns exhibit different kinds of smiles during wake and active sleep to two month-old infants and if the communicative context can affect the quantity and quality of these smiles. The aim of this study was to test if different kinds of communication affects the amount and the quality of smiles during different behavioural states. Smiling behaviour was analyzed during interactive wake (IW) and active sleep (AS), in 40 newborns randomly assigned to 4 groups of 10 newborns each: continuous tactile communication group, discontinuous non periodic tactile communication group, discontinuous periodic tactile communication group, absent communication group. In the total sample the open/closed mouth (social/non social) smiles ratio was 38/5 during IW and 1/28 during AS (p < .001). Moreover these ratios were different between the four groups. Different kinds of tactile communication affect amount and quality of the smiles of newborns during IW and AS. Moreover the morphological difference of the smiles during IW and AS suggested that for newborns the smiling behaviour during IW could have a social meaning, as it does for two month-old infants.

Respiratory inductive plethysmography (RIP) is a well-accepted noninvasive technology for monitoring breathing patterns in adults. Prior attempts to calibrate this device in babies have been fraught with technical difficulties, thereby limiting applications in this population. Recently, a new method, qualitative diagnostic calibration (QDC), has been shown to provide accurate calibration of tidal volume in adults. The QDC method is based upon principles of the isovolume maneuver and carried out during natural breathing without specialized respiratory maneuvers or postural changes. We calibrated RIP with QDC in the supine posture and compared tidal volume (VT) measured with RIP to VT by a face mask-pneumotachograph (PNT) in 21 healthy full-term newborns in supine and prone postures. Eleven of the babies were calibrated during active sleep and 10 in quiet sleep. The mean VT in the supine and prone postures were 19 and 25 ml, respectively. In the supine and prone postures, weighted mean difference between RIP (VT) and PNT (VT) and 95% confidence intervals were -0.05 ml (-0.27, 0.18) and -0.32 ml (-0.08, 0.55), respectively. There was no difference in the accuracy of RIP relative to PNT calibrated during active sleep when thoracoabdominal incoordination was present or quiet sleep when it was not in either the supine or the prone postures. Therefore, in full-term infants, RIP calibrated with QDC solely in the supine posture provides clinically acceptable measurements of VT in both supine and prone postures.

Neonatal sleep behaviors and behavioral state cycling were observed for 20 pairs of same-sex, fullterm twins in which one twin of the pair was appropriate-for-gestational-age (AGA) and the other twin was small-for-gestational-age (SGA). Time-sampling recordings were made in active sleep of number and vigor of limb movements, body and head movements, and mouth movements. No group differences were observed for time spent in first active sleep, first quiet sleep, or length of first sleep cycle. Examination of specific behaviors indicated a significantly higher incidence of vigorous limb movements and right hand-to-mouth movements, with a trend for more small limb movements and left hand-to-face movements, for AGA twins when compared with SGA twins. SGA twins had significantly more spontaneous smiles and a trend for more spontaneous startles than AGA twins. A stepwise discriminant analysis indicated that a composite of the variables smile, large limb movement, startle, and left hand-to-face significantly discriminated between the two groups, with 90% correct classification of the AGA twins and 75% correct classification of the SGA twins. The results demonstrated the utility of evaluating specific sleep behaviors, rather than state cycling only, to describe differences in neonatal sleep characteristics between AGA and SGA twins.

Experiments were done to determine if endogenous opiates cause the arousal response decrement that follows repeated exposure to hypoxemia during sleep in lambs. Five lambs were anesthetized and instrumented for sleep staging and measurement of arterial Hb oxygen saturation. No sooner than 3 d after surgery, measurements were made in quiet sleep and active sleep during control periods when the lambs were breathing 21% oxygen and during experimental periods when the lambs were breathing 5% oxygen. The experimental period was terminated during each epoch by changing the inspired gas mixture back to 21% oxygen, once the lamb aroused from sleep. After each lamb had been exposed to 5% oxygen during 100 consecutive epochs of sleep, naloxone—an opiate antagonist—was given i.v. in a dose of 3 mg/kg as a bolus. The animals continued to be exposed to 5% oxygen during six more epochs of sleep after the administration of naloxone. Arousal occurred from both sleep states during rapidly developing hypoxemia but was delayed in active sleep compared to quiet sleep. The arterial Hb oxygen saturation at arousal was significantly lower, and the time to arousal was significantly longer with repeated exposure to hypoxemia during both quiet sleep and active sleep. Naloxone did not alter this arousal response decrement to hypoxemia. Thus, our data provide evidence that endogenous opiates do not play a major role in causing the arousal response decrement that follows repeated exposure to hypoxemia during sleep in lambs.

The present paper investigates the neural ontogeny of newborns in view of electroencephalogram (EEG) complexity during active sleep (AS) and quiet sleep (QS). Sample entropy (SampEn) is applied to EEG recordings from 168 newborns with postmenstrual age (PMA) ranging from 25 to 60 weeks. The relationship between neurodevelopment and PMA is then explored according to the statistical analysis of the median and interquartile range of SampEn curves. It is found that SampEn of EEG during AS is higher than that during QS. SampEn increases during both AS and QS before about 42 weeks in PMA while it ceases its increase in QS and even decreases in AS after newborns reaching term age. A distinct decrease in the interquartile range of SampEn is found with increasing PMA (from 25 to about 50 weeks), followed by maintenance of low fluctuation in SampEn curves. The study in this paper sets the stage for exhaustive investigation of the SampEn of EEG during brain maturation in newborns. And it could be hoped that SampEn in sleep EEG might be a useful parameter against which delays and aberrations in brain maturation might be tested. The SampEn changes during brain maturation also offer functional clues about neurodevelopment, based on which further explorations could be done. The significance of this paper is the discovery of the decrease in EEG complexity after newborns reaching term. Although some potential neurophysiologic reasons are given, this new discovery might require more study to investigate. In addition, the fluctuation of EEG complexity is analyzed for the first time, which helps to understand the EEG maturation in neurodevelopment.

Knowledge of the sleep state is important in physiological studies since many physiological variables show different properties in different sleep states. The recently developed static charge sensitive bed (SCSB) method allows long-term recordings of body movements, respiration and ballistocardiogram without electrodes attached to the subject. The recordings are easy to carry out and they do not disturb the subject in any way. The recorded variables are basic characteristics of different sleep states. SCSB-recordings and electroencephalography (EEG) based polygraphy as well as blind sleep state scoring were carried out in 8 newborn infants. The positive correlation between SCSB-scoring and EEG-based polygraphy scored by two clinical neurophysiologists was 68.1 and 64.1%. Only in 2% of all epochs was active sleep scored as quiet sleep or vice versa. The results indicate the usefulness of the SCSB method in sleep state scoring of newborn infants.

INTRODUCTION: Fetus and neonate spend most of their time sleeping inside and outside the womb. Sleep is considered a crucial action of neonatal period similar to breathing and nutrition. It plays a key role in brain development. Today, it is shown that sleep plays a predominant role in body temperature regulation, energy saving and neuronal detoxification. Sleep is the most important behavioral state of neonates, particularly in preterm ones. Noise, light, invasive treatment and caring activities are among disturbing factors in the neonatal intensive care unit (NICU) that leave negative impacts on brain development through disturbing the sleep process. MATERIALS & METHODS: This descriptive study assessed all NICU nurses of Ali-ibn-Abitaleb hospital using the census sampling method. Demographic data was collected through a questionnaire with 10 questions about active sleep (AS) cycles, also referred to as REM, methods for inducing AS and AS specifications in neonates. The questionnaire was distributed between the nurses. After completion, data was analyzed using SPSS 16 and descriptive statistics method. FINDINGS: According to analyses, 24%, 20%, 48% and 92% of nurses gave correct answers to questions about AS cycle, AS in neonates, the role of sleep in saving energy and ideal noise level, respectively.CONCLUSION: According to results, nurses had a low level of knowledge towards neonatal sleep. All nurses need to know the importance of sleep in preterm neonates. The main role of inducing sleep is to protect the development of the neonates’ brain in the NICU. Those nurses who spend a remarkable portion of their time for caring neonates in the NICU play a significant role in neonatal sleep care.

This study examined whether 3–15 month-old cosleeping infants displayed differences in time spent in active versus quiet sleep, and in the number/duration of nighttime awakenings when compared with solitary-sleeping infants; and also whether they spent the majority of the night sleeping face-to-face, as previously reported. Nine cosleeping and nine solitary-sleeping infants were matched on age, gender, ethnicity, maternal age, and family SES. Video recordings of nighttime sleep yielded percentage of time in active sleep, quiet sleep, and awake, number of awakenings, and the percentage of time cosleeping infants and mothers spent face-to-face. Across age, cosleeping infants had more awakenings per night (mean 5.8(1.50) versus 3.2(1.95); t = 3.16, p = .006). The percent of the nighttime spent awake did not differ between groups, suggesting that cosleeping infants had shorter awakenings. Cosleeping infants spent 40% of the night face-to-face with their mothers.

To investigate whether a history of maternal tobacco smoking affected the maturation of arousal responses and whether sleeping position and infant age alters these relations.Healthy term infants (13 born to mothers who did not smoke and 11 to mothers who smoked during pregnancy) were studied using daytime polysomnography on three occasions: (a) two to three weeks after birth, (b) two to three months after birth, and (c) five to six months after birth. Multiple measurements of arousal threshold in response to air jet stimulation were made in both active sleep (AS) and quiet sleep (QS) when infants slept both prone and supine.Maternal smoking significantly elevated arousal threshold in QS when infants slept supine at 2-3 months of age (p0.05). Infants of smoking mothers also had fewer spontaneous arousals from QS at 2-3 months in both prone (p0.05) and supine (p0.001) sleeping positions. In infants of non-smoking mothers, arousal thresholds were elevated in the prone position in AS at 2-3 months (p0.01) and QS at 2-3 weeks (p0.05) and 2-3 months (p0.001).Maternal tobacco smoking significantly impairs both stimulus induced and spontaneous arousal from QS when infants sleep in the supine position, at the age when the incidence of sudden infant death syndrome is highest.

Quiet sleep (QS) is usually assumed to have evolved before active sleep (AS), because early studies of the primitive mammal echidna indicated that it experiences QS only. Theories designed to account for the development of AS therefore usually focused on the adaptive advantages of a QS/AS cycle over QS alone. There are several conceptual and empirical problems with those theories, however. Moreover, recent data indicate that a QS/AS cycle is extant in all mammals and birds. Empirical and conceptual evidence supporting the notion that AS developed earlier than previously thought, and that AS could have preceded QS in evolution, are discussed here.