Maternal Differentiation of Self and Toddlers' Sleep: The Mediating Role of Nighttime Involvement.

Good sleep is essential for optimal development and adaptive functioning. Hence, identifying the factors that shape sleep quality is important. Based on the transactional model of sleep development and drawing on Bowen's concept of differentiation of self (DoS), the present study examined the interrelations between sleep-related parental behavior, child's sleep quality, and mothers' DoS. A community sample of 130 mothers of 24- to 36-month-old children completed the DoS instrument and sleep questionnaires. Lower maternal DoS levels were associated with higher parental sleep-related involvement, both at bedtime and through the course of the night. Using structural equation modeling (SEM), a path analysis model indicates that maternal sleep-related involvement functions as a mediator through which the differentiation of self is related to the sleep characteristics of toddlers. As the links between parenting practices and child sleep reflect bi-directional associations, the conclusion that can be drawn from the present data is that relational aspects, such as those defined and measured by the construct of DoS, contribute to sleep-wake regulation beyond infancy. The data suggest that this construct should be considered in intervention research.

Infant motor development predicts the dynamics of movement during sleep.

The characteristics of infant sleep change over the first year. Generally, infants wake and move less at night as they grow older. However, acquisition of new motor skills leads to temporary increases in night waking and movement at night. Indeed, sleep-dependent movement at night is important for sensorimotor development. Nevertheless, little is known about how movement during sleep changes as infants accrue locomotor experience. The current study investigated whether infant sleep and movement during sleep were predicted by infants' walking experience. Seventy-eight infants wore an actigraph to measure physical activity during sleep. Parents reported when their infants first walked across a room >10 feet without stopping or falling. Infants in the midst of walking skill acquisition had worse sleep than an age-group estimate. Infants with more walk experience had more temporally sporadic movement during sleep and a steeper hourly increase in physical activity over the course of the night. Ongoing motor skill consolidation changes the characteristics of movement during sleep and may alter sleep state-dependent memory consolidation. We propose a model whereby changes in gross motor activity during night sleep reflect movement-dependent consolidation.

The unique contributions of day and night sleep to infant motor problem solving.

The current study sought to tease apart the unique contributions of napping and nighttime sleep to infant learning, specifically in the context of motor problem solving. We challenged 54 walking infants to solve a novel locomotor problem at three time points-training, test, and follow-up the next morning. One group of infants napped during the delay between training and test. Another group did not sleep during the delay. A third group received the test immediately after training with no delay. Only the Nap group's strategy choices continued to improve through the follow-up session, suggesting that daytime sleep has an active role in strengthening otherwise fragile memory. Although group did not affect strategy maintenance, walk experience did, suggesting that task difficulty may shape the impact of sleep on learning. Thus, day sleep and night sleep make independent contributions to the consolidation of motor problem-solving strategies during infancy.

Night Sleep and Parental Bedtime Practices in Low-Risk Preterm and Full-Term Late Talkers.

Night sleep and parental bedtime practices have rarely been investigated in late talkers. This study aimed to explore: night sleep, parental bedtime practices, and their associations in late talkers as well as individual, socio-demographic, and socio-relational factors affecting them. Parents of 47 30-month-old late talkers, born low-risk preterm (n = 24) or full-term (n = 23), with an expressive vocabulary size ≤10th percentile measured by the MacArthur-Bates Communicative Development Inventory Words and Sentences, and normal cognitive abilities measured by the Bayley Scales, completed the Infant Sleep Questionnaire, the Parental Interactive Bedtime Behaviour Scale, and the Parenting Stress Index Short Form. Results showed slight settling difficulties, night wakings, and frequent co-sleeping in late talkers. Encouraging autonomy practices were frequently used by parents, rather than active physical comforting ones. Recurrent settling difficulties were reported by parents who often applied encouraging autonomy practices, whereas greater night waking problems and frequent co-sleeping were reported by parents who often left their child crying. Low-risk preterm birth and mother's parenting stress predicted total sleep difficulties and night wakings; first-born, high maternal education level and mother's parenting stress predicted settling difficulties; mother's parenting stress was the only predictor for co-sleeping and leaving to cry. These findings have relevant implications for improving late talkers' night sleep and their parents' bedtime practices.

Exposure to War Prior to Conception: Maternal Emotional Distress Forecasts Sex-Specific Child Behavior Problems.

OBJECTIVES: Exposure to maternal stress during the prenatal period adversely affects child outcomes. Recent investigations have shifted to an even earlier period, the preconception period, to better understand the role of this formative period in human health and disease. We investigated the links between maternal emotional distress following preconception exposure to war, and child outcomes at age 10. MATERIAL AND METHODS: Before becoming pregnant, mothers were exposed to missile bombardment on the north of Israel in the 2006 war. Mothers who conceived within 12 months after the war were recruited and compared to mothers who conceived during the same period but lived in Israel but outside missile range. During the initial assessment, mothers completed a questionnaire on emotional distress. At 10 years of age, mothers and children (N = 68) reported on child socio-emotional outcomes. RESULTS: Multiple regression analyses revealed that, in girls, higher maternal emotional distress following preconception war exposure predicted more internalizing and externalizing behavior problems, and more behavior regulation problems. In boys, maternal emotional distress was not significantly related to outcomes. CONCLUSION: Maternal emotional distress following preconception exposure to war forecasts sex-specific child behavioral problems as reported by the mother and the child. Though the results warrant cautious interpretation because of the relatively small sample size and differential attrition, our findings add to the small but growing body of research on the consequences of maternal stress exposure prior to conception for the next generation.

Nap timing makes a difference: Sleeping sooner rather than later after learning improves infants' locomotor problem solving.

Twenty-nine newly-walking infants who had recently given up crawling trained to navigate a shoulder-height, nylon tunnel to reach a caregiver waiting at the other end. Infants in the Nap First group napped within 30 min of initial training. Infants in the Delay First group napped four hours after training. All infants were retested six hours after training on the same locomotor problem. Learning was measured by the number of training prompts required to solve the task, exploration, and time to solve the problem. Nap First infants benefited the most from a nap; they required fewer training prompts, used fewer posture shifts from training to test, and solved the task faster compared to Delay First infants, suggesting that optimally timed sleep does not merely protect against interference, but actively contributes to memory consolidation. This study highlights the importance of nap timing as a design feature and was a first step towards limit-testing the boundaries of the relation between sleep and learning. Infants' fragile memories require regular consolidation with intermittent periods of sleep to prevent interference or forgetting.

Newly walking infants' night sleep impacts next day learning and problem solving.

Sleep is part of the process that prepares children and adults for next day cognitive activity. Insufficient or fragmented sleep has a detrimental impact on subsequent encoding (Rouleau et al., 2002) and cognitive functioning (Joo et al., 2012). However, fragmented sleep early in life is a developmental norm, limiting the extent to which conclusions derived from older populations can be generalized. To directly test the continuity of this relationship, newly-walking infants' (N=58) sleep was monitored overnight using actigraphy. The next morning they were taught a motor problem-solving task. The task required infants to navigate through a tunnel to reach a goal at the other end. We coded infants' exploratory behaviors and the extent of training required to solve the task. Using a cluster analysis that accounted for exploratory behaviors and number of training prompts, infants were sorted into three profiles: those who found the task Easy to solve, those who found it Difficult, and those who Never solved it. Wake episodes and sleep efficiency were entered as predictors of cluster membership in a multinomial logistic regression. Of the infants who ultimately solved the task, those with more wake episodes and lower sleep efficiency had more difficulty. Specifically, fragmentation appeared to negatively impact preparedness to learn. Contrary to our expectations, infants who Never solved the task had the least fragmented sleep, indicating that an optimal level of fragmentation is needed for efficient problem-solving. For infants, some level of sleep fragmentation is needed the night before learning in order to solve a task efficiently. These findings highlight the interaction between developmental domains, from sleep quality to motor experience, and their impact on infant learning in real time.

The contribution of good sleep to working memory in preschool: A matter of sleep quality or duration?

Good sleep is essential for efficient cognitive performance. The present research examined the link between sleep and working memory (WM) during early childhood, a period of major advances in neurodevelopment. The sample included 80 healthy children, 40 3-year-olds and 40 4-year-olds, attending childcare settings. The children were individually tested using WM tasks; parents completed sleep questionnaires. On a group level, WM improved with age. Process model analysis demonstrated the effect of age on WM (P=0.001) and indicated an age-specific involvement of sleep quality (P=0.01). Whereas sleep duration was not associated with WM, at 4years of age, sleep disturbance with physical symptoms (e.g., breathing, motor) was associated with poor WM performance. Among 3-year-old girls, fear-related sleep disruption was associated with better WM performance. Together, the results suggest that the association between sleep and WM is dependent on: (a) specific aspects of sleep, (b) age, and (c) gender. More research is essential for unraveling the underlying neuro-maturational processes and mechanisms.

Infant motor activity during sleep: Simultaneous use of two actigraphs comparing right and left legs.

Motor asymmetry during the first hours of sleep documented in adults found higher activity in the non-dominant limb. The stage of development at which such asymmetries first appear is unknown. Twenty healthy infants were followed from 7 to 12months of age, at 3-week intervals, comparing motor activity of the right and left legs during sleep using twin actigraphs (AMI). Hour-by-hour analysis of the first seven hours of nocturnal sleep found no consistent difference in activity levels between the right and left legs. Using the standard algorithm for infants, which provides an overall estimate of sleep quality, revealed discrepancies in night waking episodes (Right versus Left) in 33% of the nights. Results pertaining to leg movement suggest that motor asymmetry is not yet present during the first year of life. However, given the large discrepancies in the detection of night waking, further investigation of the developmental course of circadian motor asymmetry is warranted.

Naps improve new walkers' locomotor problem solving.

In this first study of the impact of sleep on infants' problem solving of a locomotor task, 28 newly walking infants who were within a week of having given up crawling trained to navigate a shoulder-height tunnel to reach a caregiver waiting at the end. During the transitional window between crawling and walking, infants are reluctant to return to crawling, making this task uniquely challenging. Infants were randomly assigned to either nap or stay awake during a delay between training and a later test session. For the Nap group, efficiency of problem solving improved from training to test, but there was no change for the No Nap group. These findings suggest that for newly walking infants, sleep facilitates learning to solve a novel motor problem.

Actigraphic motor activity during sleep from infancy to adulthood.

A secondary analysis of longitudinal and cohort studies was carried out to quantitatively investigate the motor activity pattern, recorded through actigraphy, during the first six hours of nocturnal sleep. The first study was of longitudinal nature. Ten healthy participants (four females) were monitored three times, at baseline (T1) when they were infants (mean age 7.10 ± 0.32 months), at the first follow-up examination (T2) around 4 months later (mean age 11.20 ± 0.63 months) and at the second follow-up (T3) around three years later, when they were preschoolers (mean age 4.68 ± 0.14 years). At T1, T2 and T3 each participant wore the actigraph Basic Mini-Motionlogger (Ambulatory Monitoring, Inc., Ardsley, NY, USA) over at least two consecutive nycthemeral cycles, with the aim to measure the mean hourly motor activity count. Seven- and 11-month-old infants had a higher level of motor activity over the night compared to preschoolers. Furthermore, motor activity increased as the night progressed, with a pronounced increment at both T1 and T2, while at T3 such an increase was less marked. The second study was cross-sectional and aimed to explore the motor activity pattern, using actigraphy, during the first six hours of nocturnal sleep in multiple-age healthy groups, from infancy to adulthood. We assigned participants to eight groups according to age: 20 (five females) aged around 10 months old (mean age 10.65 ± 0.67 months); 13 (nine females) aged around 4 years (mean age 4.38 ± 0.51 years); 21 (10 females) aged around 10 years (mean age 9.67 ± 0.91 years); 21 (nine females) aged around 20 years (mean age 19.33 ± 2.44 years); 20 (10 females) aged around 30 years (mean age 29.80 ± 1.99 years); 20 (15 females) aged around 40 years (mean age 40.70 ± 1.26 years); 20 (11 females) aged around 50 years (mean age 50.15 ± 2.80 years) and 20 (nine females) aged around 60 years (mean age 59.25 ± 3.23 years). The participants aged between 10 and 60 years wore the actigraph Basic Mini-Motionlogger over seven consecutive nycthemeral cycles (infants and preschoolers wore the actigraph over at least two consecutive nycthemeral cycles), with the aim to measure the mean hourly motor activity count. The results indicated a significantly higher motor activity count in 10-month-old infants compared to all the remaining age groups. Moreover, the pattern of motor activity of 10-month-old infants was different from that of all other groups, with the highest motor activity counts from the second to the sixth hour of sleep. Considered as a whole, the results of both studies converge regarding the high motor activity detected among infants, which could be explained by the presence of a maturational process that has not yet been fully completed at this stage of life. In both studies, only the motor activity of infants was above the cutoff level established for normal adults, highlighting the need to establish a specific cutoff value for infants.

Sleep Problems in Young Children with Autism Spectrum Disorders: A Study of Parenting Stress, Mothers' Sleep-Related Cognitions, and Bedtime Behaviors.

INTRODUCTION: Disrupted sleep is common among children with autism spectrum disorder (ASD). AIMS: Our goal was to (1) examine the contribution of sleep problems to parenting stress in children with ASD as compared to typically developing (TD) and (2) to address maternal sleep-related cognitions and behaviors in both groups. METHODS: Mothers of 34 ASD (mean age = 39.29 months, SD = 5.22) and 31 TD children (mean age = 36.23 months, SD = 5.75) completed questionnaires measuring maternal stress, sleep-related cognitions and settling to sleep interactions, and the child's sleep problems; mothers in the ASD group completed a symptom severity questionnaire. RESULTS: In accord with previous research, children with ASD had more sleep problems compared to the TD group, and their mothers reported higher levels of stress. In the ASD group, sleep problems contributed to the experience of maternal stress, over and above symptom severity. Across groups, maternal cognitions and bedtime interactions were significantly associated with children's sleep problems. CONCLUSION: The results highlight the interplay between sleep-related cognitions, bedtime interactions, and sleep problems and underscore the contribution of disrupted sleep to mothers' experience of parenting stress. As sleep problems in ASD children are common, clinicians are advised to include sleep in consultations with parents.

Sleep disruption and motor development: Does pulling-to-stand impacts sleep-wake regulation?

During the second half of the 1st year, periods of increased sleep disruption have been documented alongside overall improvement in sleep-wake regulation. The objective of the present research was to test if pulling-to-stand (PTS), a milestone typically achieved during the latter part of the 1st year, co-occurs with a period of disrupted sleep. In a longitudinal design, 20 healthy infants were followed-up, from 7 to 11-12 months, at 3-week intervals. Each measurement consisted of filmed motor observations and sleep recordings (actigraphy), both conducted at home. It was found that among early achievers of PTS (by 8 months), the milestone was time-linked to a period of disrupted sleep. The results point to the significance of timing in the interplay between domains of development, and highlight the importance of considering both chronological and developmental metrics in studying changes in sleep-wake regulation.

Sleep as a mirror of developmental transitions in infancy: the case of crawling.

The associations between the onset of crawling and changes in sleep were examined in 28 infants who were followed from 5 to 11 months-of-age. Motor development and sleep (actigraphy) were assessed at 2- to 3-week intervals. Along with the overall improvement in sleep consolidation, periods of increased long wake episodes were also manifested; the rise in sleep disruption was temporally linked to crawling onset. The results of the study highlight the dynamic interrelations between domains of development, indicate that emerging motor skills may involve periods of disrupted sleep, and point to the moderating effect of age. Clarifying the factors involved in the interplay between developmental milestones and sleep remains a challenge for future research.

Assessing motivation to move and its relationship to motor development in infancy.

Motivation to move has typically been a post hoc explanation for infants' discovery of new patterns of behavior. As a first step to studying motivation to move directly, we qualitatively assessed motivation to move and measured its relationship to motor development in infancy. We observed 27 infants longitudinally from ages 7 to 12 months. Every 3 weeks we assessed infants' motor motivation based on persistence, activity level, activity preference, and stimulus strength needed to elicit movement. We documented the onset of sitting, pulling-to-stand, crawling and cruising, as well as infants' overall motor development as measured with the Alberta Infant Motor Scale (AIMS). Motor motivation increased over the course of the study and we identified two distinct motivation profiles. Strongly motivated infants had earlier onsets for all four motor milestones than weakly motivated infants (all p-values <0.05). Infants' motivation to move score was positively correlated with their AIMS percentile at the same and subsequent sessions. These findings provide empirical evidence for a motivational cascade whereby motivation to move and motor development enjoy a reciprocal relationship. These findings have important clinical implications for children with motor delay, suggesting that evaluation of motivation could be included as part of the assessment procedure so that both treatment and expectations can be tailored appropriately.

Seasonal effect on infants' sleep regulation: a preliminary study in a Mediterranean climate.

Infants' sleep-wake rhythms are influenced by multiple factors, including developmental and contextual aspects, as well as circadian cycles. Empirical studies that address the seasonal impact on infants' sleep are scarce. The present study examined aspects of sleep schedule and quality, comparing summer and winter months in a Mediterranean climate. This report is based on a convenience sample of 34 healthy 7-mo-olds, an age in which sleep is well consolidated and regulated compared with the first few months of life. Sleep was measured with actigraphy, in the home context. It was found that compared with winter, in the summer months, sleep onset occurred at a later hour, and more motor activity during sleep was detected. Although the overall sleep quality, as defined by sleep efficiency score, was similar in the two seasons, in the summer, more active sleep was observed. The authors discuss the finding in terms of circadian rhythms, developmental characteristics, as well as possible environmental factors and family routines, and call for more studies, in different climates and geographical zones, and in different developmental periods.

Continuity and change in infants' sleep from 8 to 14 months: a longitudinal actigraphy study.

In this report changes and stability in sleep-wake characteristics, at the latter part of infancy, were examined. The sample comprised of 34 healthy infants whose sleep was assessed by means of actigraphy at 8, 10, 12 and 14 months. The results indicated that while sleep schedules did not change significantly from 8 to 14 months, sleep consolidation continued across time. Age 12 months stands out in that sleep disruption was unrelated to whether or not the child was a frequent nightwaker before and/or after the 1st birthday. The findings demonstrate the importance of investigating sleep longitudinally using multiple time scales.

Pulling to stand: common trajectories and individual differences in development.

This longitudinal study of 27 infants examined the development of pulling-to-stand (PTS). In general, infants began PTS using a two-leg strategy and transitioned to a half-kneel strategy. As a group, infants showed no preference for either strategy at the onset of PTS, switching between strategies until half-kneeling became the dominant pattern about 1 month after the onset of PTS. Examination of individual developmental trajectories revealed variability in age at PTS onset, time between PTS onset and half-kneel strategy onset, duration of the two-leg strategy as the dominant pattern, time until the half-kneel strategy became the dominant pattern, shape of the transition between strategies (gradual vs. abrupt), and timing of PTS relative to onset of other motor milestones. We discuss variation in developmental trajectory in terms of adaptive behavior during the acquisition of new skills and as a process shaped by infants' unique experiences prior to and during the acquisition period.

Parenting and infant sleep.

Infant sleep undergoes dramatic evolution during the first year of life. This process is driven by underlying biological forces but is highly dependent on environmental cues including parental influences. In this review the links between infant sleep and parental behaviors, cognitions, emotions and relationships as well as psychopathology are examined within the context of a transactional model. Parental behaviors, particularly those related to bedtime interactions and soothing routines, are closely related to infant sleep. Increased parental involvement is associated with more fragmented sleep. Intervention based on modifying parental behaviors and cognitions have direct effect on infant sleep. It appears that parental personality, psychopathology and related cognitions and emotions contribute to parental sleep-related behaviors and ultimately influence infant sleep. However, the links are bidirectional and dynamic so that poor infant sleep may influence parental behaviors and poor infant sleep appears to be a family stressor and a risk factor for maternal depression.