Cortisol, contingency learning, and memory in preterm and full-term infants

Science of interdisciplinary salivary bioscience: history and future directions

Salivary bioscience is noteworthy in its history, as well as in the breadth and scope of its impact. The minimally invasive nature of sampling oral fluid allows for evaluation of individual and intra-individual change in biological processes in ways and settings not possible with traditional biospecimens. The range of measurements is expansive (e.g., DNA, hormones, cytokines, antibodies) and modern technologies enable simultaneous multisystem assessment from a singlet specimen. Used in combination with modern multivariate analytical models, the capacity to repeatedly assess multisystem and level measurements collected from the same individual over time enable operationalization, testing and refinement of complex biobehavioral models. This review describes the emerging narrative of salivary bioscience, and aims to inform and reveal opportunity for innovation and discovery.

Saliva cortisol diurnal variation and stress responses in term and preterm infants

OBJECTIVE

To determine if preterm birth is associated with adaptation of the hypothalamic-pituitary-adrenal (HPA) axis and whether HPA axis programming relates to the degree of prematurity (defined as extremely preterm birth at <28 weeks or very preterm birth at 28-32 weeks gestation).

DESIGN

This study reports findings from a prospective birth cohort. Saliva cortisol concentrations were measured prevaccination and postvaccination, and in the morning and evening, at 4 months chronological age.

SETTING

Infants born at a single Scottish hospital.

PARTICIPANTS

45 term-born, 42 very preterm and 16 extremely preterm infants.

OUTCOMES

Cortisol stress response to vaccination (postvaccination minus prevaccination cortisol concentrations), diurnal slope (log-transformed morning minus log-transformed evening cortisol values) and mean log-transformed daily cortisol.

RESULTS

Compared with infants born at term, infants born extremely preterm had a blunted cortisol response to vaccination (5.8 nmol/L vs 13.1 nmol/L, difference in means: -7.3 nmol/L, 95% CI -14.0 to -0.6) and a flattened diurnal slope (difference in geometric means: -72.9%, 95% CI -87.1 to -42.8). In contrast, the cortisol response to vaccination (difference in means -2.7 nmol/L, 95% CI -7.4 to 2.0) and diurnal slope at 4 months (difference in geometric means: -33.6%, 95% CI -62.0 to 16.0) did not differ significantly in infants born very preterm compared with infants born at term.

CONCLUSIONS

Infants born extremely preterm have blunted cortisol reactivity and a flattened diurnal slope. These patterns of HPA axis regulation are commonly seen after childhood adversity and could contribute to later metabolic and neurodevelopmental phenotypes observed in this population.

A New Perspective on Assessing Cognition in Children through Estimating Shared Intentionality

This theoretical article aims to create a conceptual framework for future research on digital methods for assessing cognition in children through estimating shared intentionality, different from assessing through behavioral markers. It shows the new assessing paradigm based directly on the evaluation of parent-child interaction exchanges (protoconversation), allowing early monitoring of children’s developmental trajectories. This literature analysis attempts to understand how cognition is related to emotions in interpersonal dynamics and whether assessing these dynamics shows cognitive abilities in children. The first part discusses infants’ unexpected achievements, observing the literature about children’s development. The analysis supposes that due to the caregiver’s help under emotional arousal, newborns’ intentionality could appear even before it is possible for children’s intention to occur. The emotional bond evokes intentionality in neonates. Therefore, they can manifest unexpected achievements while performing them with caregivers. This outcome shows an appearance of protoconversation in adult-children dyads through shared intentionality. The article presents experimental data of other studies that extend our knowledge about human cognition by showing an increase of coordinated neuronal activities and the acquisition of new knowledge by subjects in the absence of sensory cues. This highlights the contribution of interpersonal interaction to gain cognition, discussed already by Vygotsky. The current theoretical study hypothesizes that if shared intentionality promotes cognition from the onset, this interaction modality can also facilitate cognition in older children. Therefore in the second step, the current article analyzes empirical data of recent studies that reported meaningful interaction in mother-infant dyads without sensory cues. It discusses whether an unbiased digital assessment of the interaction ability of children is possible before the age when the typical developmental trajectory implies verbal communication. The article develops knowledge for a digital assessment that can measure the extent of children’s ability to acquire knowledge through protoconversation. This specific assessment can signalize the lack of communication ability in children even when the typical trajectory of peers’ development does not imply verbal communication.

"Does your baby watch TV?": The associations between at-home TV watching and laboratory challenge cortisol are different for young infants and their mothers

This longitudinal study examined associations between at-home TV watching and the biological stress response (cortisol) during a laboratory infant cognitive challenge task in 240 3- and 5-month infants and their mothers. Cortisol levels were lower in mothers of 5-month-old infants whose infants were exposed to TV at home, compared to mothers of infants that were not TV-exposed. Cortisol patterns were different across three laboratory sampling intervals for 3-month-old infants as a function of TV watching, revealing a sharp increase in laboratory cortisol only for infants who were exposed to TV at home. In contrast, there was no effect of TV exposure in 5-month-old infants' cortisol. Infant temperament and demographic measures were included as control variables in regression models to predict maternal and infant cortisol. At 3 months, for the T3 cortisol sampling interval, and at 5 months across all three sampling intervals, maternal cortisol levels were significantly predicted by infant TV exposure after accounting for variance due to these control variables. Our findings show the strong influence of the infant TV-exposure factor in the biological stress response of mothers of young infants, and suggest that infant TV exposure may influence self-regulation in 3-month-old infants.

Effects of a tripartite intervention on biological stress in preterm infants during heel pricks for newborn screening: A randomized controlled trial

This prospective randomized trial examined the effects of a tripartite intervention (behavioral state modulation + nonnutritive sucking + tucking) on stress from procedural pain during heel pricks. Blood samples for routine screening were collected by heel pricks 48 h after birth (Stage 1) and at ≥37 weeks' gestation (Stage 2); salivary cortisol levels (SCLs) pre-prick (T0) and 20 min post-prick (T1) assessed stress. Preterm infants (n = 64) sampled by convenience at Level III neonatal care units were randomly assigned to the control condition (usual care) or intervention condition (tripartite intervention). Generalized estimating equations examined differences in salivary cortisol between conditions. After adjusting for effects of gestational age, postmenstrual age, and baseline SCLs, (1) at Stage 1, the change in salivary cortisol from T0 to T1 in preterm infants who received the tripartite intervention was, on average, significantly lower by 0.431 units (log scale) than the change in preterm infants who received the control condition (p < 0.001); (2) in the tripartite intervention condition, the difference between the change in mean SCLs from T0 to T1 at Stages 1 and 2 was significantly lower by 0.287 units (log scale), on average than between the change at Stages 1 and 2 in the control condition (p = 0.026). The provision of a tripartite intervention during heel prick significantly decreased the raise of SCLs compared with infants receiving usual care, suggesting lower stress. Clinicians could easily implement the tripartite intervention for heel-stick support; however, replication is needed before recommending its incorporation into routine heel stick and other stressful procedures.

The Long-Term Effects of Neonatal Inflammatory Pain on Cognitive Function and Stress Hormones Depend on the Heterogeneity of the Adolescent Period of Development in Male and Female Rats

Exposure to stress at an early age programs the HPA axis which can lead to cognitive deficits in adults. However, it is not known whether these deficits emerge in adulthood or are expressed earlier in life. The aims of the study were to investigate (1) the immediate effects of early injury-induced stress in one-day-old (P1) and repeated stress on at P1 and P2 rat pups on plasma corticosterone levels; and (2) examine the subsequent long-term effects of this early stress on spatial learning and memory, and stress reactivity in early P26-34 and late P45-53 adolescent male and female rats. Intra-plantar injection of formalin induced prolonged and elevated levels of corticosterone in pups and impaired spatial learning and short- and long-term memory in late adolescent males and long-term memory in early adolescent females. There were sex differences in late adolescence in both learning and short-term memory. Performance on the long-term memory task was better than that on the short-term memory task for all early adolescent male and female control and stressed animals. Short-term memory was better in the late age control rats of both sexes and for formalin treated females as compared with the early age rats. These results are consistent with an impaired function of structures involved in memory (the hippocampus, amygdala, prefrontal cortex) after newborn pain. However, activation of the HPA axis by neonatal pain did not directly correlate with spatial learning and memory outcomes and the consequences of neonatal pain remain are likely multi-determined.

Social Network and Behavioral Synchrony Influences On Maternal and Infant Cortisol Response

This study examined the contributions of mothers' social network stability and mother-infant behavioral synchrony on cortisol response in infants and their mothers during separation. The quality and stability of mothers' social network system and mother-infant bond have both been shown to affect infant neuroendocrine response. Yet, no studies have directly addressed how these two forms of social relationships might differentially affect infants' and mothers' neuroendocrine responses during separation. First-time mothers (N = 133) and their 3-month-old infants participated in the study. Maternal social network stability, mother-infant behavioral synchrony, and mother and infant cortisol response during an infant challenge task were assessed. Behavioral synchrony accounted for significant variance in infants' cortisol response, and after adjusting for synchrony, mothers' network stability measures did not explain variance in infant cortisol. Social network stability, but not synchrony, accounted for significant variance in mothers' cortisol response. These results demonstrate that, when mothers and infants experience brief separation, the quality of their bond is associated with a lower stress response for infants; but for mothers, it is the longevity of her social relationships outside of the mother-infant relationship context that is associated with her lower stress response.

Does texting interrupt imitation learning in 19-month-old infants?

Observed disruptions to parent-child interactions during parental media use, such as texting, have been termed technoference. For example, when a language learning interaction was disrupted by a phone call, toddlers were less likely to acquire the word. Other studies demonstrated that parents often exhibit a still face while silently reading information on their cell phones. In the present study, the effect of a text interruption on infant imitation learning was examined. Parents demonstrated three target actions to their infants and then infants were given the opportunity to repeat those interactions. The actions were demonstrated four times. Text interruptions occurred before or between demonstrations. Performance of these groups was compared to a baseline control group where the infant did not see a demonstration of the target actions and a no-interruption group where the parents demonstrated the target actions four times without interruption. Parents were randomly assigned to three conditions, interruption-first condition, one-interruption condition, or three-interruptions condition. Infant behavior was measured during the interruptions. Across text interruption groups parents exhibited high levels of still face during the interruptions (77 %). However, infants in all 3 interruption groups performed significantly above the baseline control indicating learning despite the interruptions. Higher reported maternal reliance on the smartphone was related to poorer imitation performance overall. In contrast, when parents reported that they found it easier to multi-task infant imitation rates were higher. These findings indicate that infants can learn under conditions of brief technoference and that individual differences in family media ecology are associated with learning.

Infants born full term and preterm increase the height of anti-gravity leg movements during a kick-activated mobile task using a scaffolded task environment

Prior research supports that infants born very preterm (PT), compared with full term (FT), have early differences in rate of learning and motor control that may hinder their ability to learn challenging motor tasks. Four-month-old infants born FT (n = 18) and PT (n = 18) participated in an infant kick-activated mobile task that was scaffolded to motivate progressively higher kicks. We found the FT group learned the association between their leg movements and mobile activation on the second day, but the PT group learned the association on the third day. Both groups of infants increased the height of their kicks on the day they learned the task, compared with their spontaneous kicking height. These findings suggest that infants born PT have the ability to learn challenging motor tasks, such as kicking high, when participating in a task environment that uses scaffolding.

The influence of prenatal experience on behavioral and social development: The benefits and limitations of an animal model

Prenatal experience is both a formative and a regulatory force in the process of development. As a result, birth is not an adequate starting point for explanations of behavioral development. However, surprisingly little is currently known regarding the role of prenatal experience in the emergence and facilitation of perceptual, cognitive, or social development. Our lack of knowledge in this area is due in part to the very restricted experimental manipulations possible with human fetuses. A comparative approach utilizing animal models provides an essential step in addressing this gap in our knowledge and providing testable predictions for studies with human fetuses, infants, and children. Further, animal-based comparative research serves to minimize the amount of exploratory research undertaken with human subjects and hone in on issues and research directions worthy of further research investment. In this article, I review selected animal-based research exploring how developmental influences during the prenatal period can guide and constrain subsequent behavioral and social development. I then discuss the importance of linking the prenatal environment to postnatal outcomes in terms of how psychologists conceptualize “innate” biases, preferences, and skills in the study of human development.

Infant Discovery Learning and Lower Extremity Coordination: Influence of Prematurity

AIMS

Preterm infants at increased risk for neurodevelopmental disabilities, including cerebral palsy, demonstrate reduced selective leg joint coordination. Full-term infants demonstrate more selective hip-knee coordination when specific leg actions are reinforced using an overhead infant mobile. The purpose of this pilot study was to determine the ability of preterm infants to: (1) perform and learn through discovery, the contingency between leg action and mobile activation, and (2) demonstrate more selective hip-knee coordination when leg actions are reinforced with mobile activation.

METHODS

At both 3 and 4-months corrected age, ten infants born very preterm and with very low birth weight participated in 2 sessions of mobile reinforcement on consecutive days.

RESULTS

The preterm group at 4-months, but not 3-months, learned the contingency between leg action and mobile activation. Preterm infants at 4-months were separated into those that learned (n = 6) and did not learn (n = 4) the contingency. As a group, preterm infants at 4-months who learned the contingency, did not demonstrate more selective hip-knee coordination when interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1.

CONCLUSIONS

Preterm infants, as compared to full-term infants, may have difficulty producing more selective hip-knee coordination during task-specific leg action.

The Energy Costs of Prematurity and the Neonatal Intensive Care Unit (NICU) Experience

Premature neonates are in an energy deficient state due to (1) oxygen desaturation and hypoxia events, (2) painful and stressful stimuli, (3) illness, and (4) neurodevelopmental energy requirements. Failure to correct energy deficiency in premature infants may lead to adverse effects such as neurodevelopmental delay and negative long-term metabolic and cardiovascular outcomes. The effects of energy dysregulation and the challenges that clinicians in the Neonatal Intensive Care Unit (NICU) face in meeting the premature infant's metabolic demands are discussed. Specifically, the focus is on the effects of pain and stress on energy homeostasis. Energy deficiency is a complex problem and requires a multi-faceted solution to promote optimum development of premature infants.

Prenatal maternal cortisol measures predict learning and short-term memory performance in 3- but not 5-month-old infants

Little is known about relations between maternal prenatal stress and specific cognitive processes-learning and memory-in infants. A modified crib-mobile task was employed in a longitudinal design to test relations between maternal prenatal cortisol, prenatal subjective stress and anxiety, psychosocial variables, and learning and memory in 3- and 5-month-old infants. Results revealed that maternal prenatal cortisol was affected by particular psychosocial variables (e.g., maternal age, whether or not the infant's grandmother provided childcare, financial status), but was unrelated to measures of maternal depression, anxiety, and stress. Although maternal prenatal cortisol was not predictive of learning or memory performance in 5-month-old infants, higher levels of basal maternal cortisol and reduced prenatal cortisol response was predictive of some learning and short-term memory measures in 3-month-old infants. These results suggest an influence of maternal neuroendocrine functioning on fetal neurological development, and the importance of separate examination of subjective and biological measures of stress.

Salivary cortisol and cognitive development in infants from low-income communities

Early stress exposure is proposed to have significant lasting effects on cognitive development. The glucocorticoid hormone cortisol, a product of the hypothalamic-pituitary-adrenal (HPA) axis, is a particular focus of research, however, the majority of past research has been based on studies of older children and adults. Evidence linking cortisol levels in infancy with cognitive development is lacking. In a large cohort sample of infants (N = 1091) oversampled for psychosocial risk, we tested whether basal cortisol levels and cortisol reactivity to emotional stressors administered at 7 and 15 months of age were associated with cognitive development measured at 15 months. Cognitive development was measured using the Mental Development Index of the Bayley Scales of Infant Development. Multiple regression analyses indicated that basal cortisol levels at 15 months, and to a lesser extent at seven months, were inversely associated with infant cognitive development after adjusting for psychosocial and obstetric risk. The findings provide some of the first evidence that HPA axis activity in infancy is associated with early cognitive development.

No association between hair cortisol or cortisone and brain morphology in children

Little is known about the relationship between the long-term hypothalamic-pituitary-adrenal (HPA) axis functioning and brain structure in children. Glucocorticoid in hair has emerged as an important biomarker of HPA activity. In this study, we investigated the associations of hair cortisol and cortisone concentrations with brain morphology in young children. We included 219 children aged 6-10 years from the Generation R Study in Rotterdam, the Netherlands. We examined cortisol and cortisone concentrations by hair analysis using liquid chromatography-tandem mass spectrometry, and assessed brain morphometric measures with structural magnetic resonance imaging. The relationships of hair cortisol and cortisone concentrations with brain volumetrics, cortical thickness, cortical surface area and gyrification were analyzed separately after adjustment for several potential confounding factors. We observed a positive association between cortisol concentrations and cortical surface area in the parietal lobe, positive associations of cortisone concentrations with thalamus volume, occipital lobe volume and cortical surface area in the parietal lobe, and a negative association between cortisone concentrations and cortical surface area in the temporal lobe in the regions of interest analyses. A negative association between cortisol or cortisone concentrations and hippocampal volume was observed in children with behavioral problems. The whole brain vertex-wise analyses did however not show any association between cortisol or cortisone concentration and brain morphometric measures after correction for multiple testing. Although some associations are noted in region of interest analyses, we do not observe clear association of hair cortisol or cortisone with brain morphometric measures in typically developing young children.

Vagal tone during infant contingency learning and its disruption

This study used contingency learning to examine changes in infants' vagal tone during learning and its disruption. The heart rate of 160 five-month-old infants was recorded continuously during the first of two training sessions as they experienced an audiovisual event contingent on their pulling. Maternal reports of infant temperament were also collected. Baseline vagal tone, a measure of parasympathetic regulation of the heart, was related to vagal levels during the infants' contingency learning session, but not to their learner status. Vagal tone levels did not vary significantly over session minutes. Instead, vagal tone levels were a function of both individual differences in learner status and infant soothability. Vagal levels of infants who learned in the initial session were similar regardless of their soothability; however, vagal levels of infants who learned in a subsequent session differed as a function of soothability. Additionally, vagal levels during contingency disruption were significantly higher among infants in this group who were more soothable as opposed to those who were less soothable. The results suggest that contingency learning and disruption is associated with stable vagal tone in the majority of infants, but that individual differences in attention processes and state associated with vagal tone may be most readily observed during the disruption phase.

Stress reactivity speeds basic encoding processes in infants

Acute stress attenuates frontal lobe functioning and increases distractibility while enhancing subcortical processes in both human and nonhuman animals (reviewed by Arnsten [2009] Nature Reviews Neuroscience, 10(6):410-422). To date however these relations have not been examined for their potential effects in developing populations. Here, we examined the relationship between stress reactivity (infants' heart rate response to watching videos of another child crying) and infant performance on measures of looking duration and visual recognition memory. Our findings indicate that infants with increased stress reactivity showed shorter look durations and more novelty preference. Thus, stress appears to lead to a faster, more stimulus-ready attentional profile in infants. Additional work is required to assess potential negative consequences of stimulus-responsivity, such as decreased focus or distractibility. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 546-555, 2016.

Salivary Cortisol Reactivity in Preterm Infants in Neonatal Intensive Care: An Integrative Review

Recently, more and more researchers have been using salivary cortisol reactivity to evaluate stress in preterm infants in the neonatal intensive care unit (NICU). The aim of this integrative literature review was to summarize the evidence of interventions leading to a change in salivary cortisol from the baseline in preterm infants in the NICU. The electronic databases of PubMed, CINAHL, Web of Science, and Scopus were searched for relevant studies. The inclusion criteria were studies with preterm infants exposed to an intervention evaluated by salivary cortisol reactivity before discharge from the NICU, which were published in English. In total, 16 studies were included. Eye-screening examination and heel lance provoked an increase in the salivary cortisol level. Music, prone position, and co-bedding among twins decreased the salivary cortisol level. Several studies reported a low rate of successful saliva sampling or did not use control groups. Future studies need to focus on non-painful interventions in order to learn more about salivary cortisol regulation in preterm infants. Moreover, these studies should use study designs comprising homogenous gestational and postnatal age groups, control groups, and reliable analysis methods that are able to detect cortisol in small amounts of saliva.

Pain-associated stressor exposure and neuroendocrine values for premature infants in neonatal intensive care

Recurrent stress during neonatal intensive care taxes the adaptive capacity of the premature infant and may be a risk factor for suboptimal developmental outcomes. This research used a descriptive, cross-sectional design and a life course perspective to examine the relationship between resting adrenocorticoid values at 37 postmenstrual weeks of age and cumulative pain-associated stressor exposure in prematurely born infants. Subjects were 59 infants born at under 35 completed weeks of gestation, who were at least 2 weeks of age, and who had been cared for in the NICU since birth. No significant relationships were identified between cortisol values and any of the study variables (number of skin breaking procedures, hours of assisted ventilation, gestational age at birth, exposure to antenatal steroids, history of severe academia, birthweight, days of age to attain birthweight, weight at testing, days of age at testing, recent pain-associated procedures, and 17-OHP value). A significant negative correlation (Spearman rank, one-tailed) between the number of skin-breaking procedures and 17-OHP values was identified (r = -.232, p = .039). Recurrent pain-associated stressor exposure may be a more important factor in explaining the variance of 17-OHP values at 37 postmenstrual weeks of age than birthweight, gestational age, or chronological age.

Quantifying Learning in Young Infants: Tracking Leg Actions During a Discovery-learning Task

Task-specific actions emerge from spontaneous movement during infancy. It has been proposed that task-specific actions emerge through a discovery-learning process. Here a method is described in which 3-4 month old infants learn a task by discovery and their leg movements are captured to quantify the learning process. This discovery-learning task uses an infant activated mobile that rotates and plays music based on specified leg action of infants. Supine infants activate the mobile by moving their feet vertically across a virtual threshold. This paradigm is unique in that as infants independently discover that their leg actions activate the mobile, the infants' leg movements are tracked using a motion capture system allowing for the quantification of the learning process. Specifically, learning is quantified in terms of the duration of mobile activation, the position variance of the end effectors (feet) that activate the mobile, changes in hip-knee coordination patterns, and changes in hip and knee muscle torque. This information describes infant exploration and exploitation at the interplay of person and environmental constraints that support task-specific action. Subsequent research using this method can investigate how specific impairments of different populations of infants at risk for movement disorders influence the discovery-learning process for task-specific action.

Behaviour problems and cortisol levels in very-low-birth-weight children

Abstract Background. There are still diverging results concerning the behaviour of children with very-low-birth-weight (VLBW) and they have been questioned to display different levels of stress hormone than normal-birth-weight (NBW) children. Aims. This study examined behaviour and the stress hormone cortisol in children with VLBW at the ages of 7 and 9 years compared with children with NBW. Results. Fifty-one VLBW and 50 NBW children were studied with the Child Behavior Checklist. Cortisol rhythm was measured through saliva samples three times a day for 2 days. VLBW children displayed more behavioural problems than NBW children, specifically social and attention problems, although still within normal ranges. They showed lower cortisol levels both at 7 and 9 years of age. No strong association between behaviour and cortisol levels was shown. Conclusion. VLBW children display more behaviour problems compared with NBW children but both groups score are within the normal range. Down-regulation of their hypothalamic-pituitary-adrenal (HPA) function in terms of lower cortisol levels is also noted.

Cortisol and cognitive function in midlife: the role of childhood cognition and educational attainment

Adult cognition and age-related cognitive decline can be influenced by dysregulation of the hypothalamic pituitary adrenal axis with concomitant changes in cortisol levels. However, very little is known about the role of childhood cognition and educational attainment in this relationship. Using data from the British 1946 birth cohort, the present study investigated: (1) associations between cortisol levels and patterns and cognitive function in midlife; (2) direct and interactive effects of childhood cognition, educational attainment and cortisol on cognitive function in midlife. Verbal memory, letter search speed and reaction time were assessed at age 60-64 years. Salivary cortisol samples (wakening, 30 min after wakening and evening) were collected at the same age. Childhood cognitive ability was measured at ages 8, 11, and 15, and educational level was reported at age 26. Associations between cortisol, childhood cognition, educational attainment and cognitive function in midlife were tested using linear regression and structural equation modelling approaches. Higher evening cortisol level was associated with slower reaction time and lower verbal memory. These associations were independent of childhood cognition and education as well as a range of other potential confounders. Childhood cognition and education were not directly associated with evening cortisol. However, there was a significant interaction effect between childhood cognition and evening cortisol on reaction time (p=.002): higher evening cortisol was associated with slower reaction time only among those with low childhood cognitive ability. There was little evidence of associations between the other cortisol measures and cognitive function.

Infant exploratory learning: influence on leg joint coordination

A critical issue in the study of infant development is to identify the processes by which task-specific action emerges from spontaneous movement. Emergent leg action has been studied by providing contingent reinforcement to specific leg movements using an overhead infant-activated mobile, however, there is limited information on the strategies used by infants to support the emergence of task-specific leg action from spontaneous movement. The purpose of this study is to (1) determine the ability of 3 month old infants to learn, through discovery, the contingency between leg action and mobile activation using a virtual threshold, and (2) identify strategies, defined by variance of the end-effectors (feet) and hip-knee joint coordination, used by infants that learned the contingency. Fourteen 3 month old infants participated in 2 sessions of mobile reinforcement on consecutive days. As a group, infants increased the percentage of mobile activation to meet performance criteria on Day 2, but did not meet memory or learning criteria across days. However, five infants learned the contingency based on individual learning criteria. When interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1, infants who learned the contingency, but not infants who did not learn the contingency, increased variance of the end-effectors (feet) in the vertical, task-specific direction and demonstrated less in-phase hip-knee joint coordination. An important discovery is that infants can discover this very specific contingency, suggesting that this movement behavior (action) can be shaped in future work. This may have implications for the rehabilitation of infants with atypical leg action.

Maternal-preterm skin-to-skin contact enhances child physiologic organization and cognitive control across the first 10 years of life

BACKGROUND

Maternal-newborn contact enhances organization of the infant's physiological systems, including stress reactivity, autonomic functioning, and sleep patterns, and supports maturation of the prefrontal cortex and its ensuing effects on cognitive and behavioral control. Premature birth disrupts brain development and is associated with maternal separation and disturbances of contact-sensitive systems. However, it is unknown whether the provision of maternal-preterm contact can improve long-term functioning of these systems.

METHODS

We used the Kangaroo Care (KC) intervention and provided maternal-newborn skin-to-skin contact to 73 premature infants for 14 consecutive days compared with 73 case-matched control subjects receiving standard incubator care. Children were then followed seven times across the first decade of life and multiple physiologic, cognitive, parental mental health, and mother-child relational measures were assessed.

RESULTS

KC increased autonomic functioning (respiratory sinus arrhythmia, RSA) and maternal attachment behavior in the postpartum period, reduced maternal anxiety, and enhanced child cognitive development and executive functions from 6 months to 10 years. By 10 years of age, children receiving KC showed attenuated stress response, improved RSA, organized sleep, and better cognitive control. RSA and maternal behavior were dynamically interrelated over time, leading to improved physiology, executive functions, and mother-child reciprocity at 10 years.

CONCLUSIONS

These findings are the first to demonstrate long-term effects of early touch-based intervention on children's physiologic organization and behavioral control and have salient implications for the care practices of premature infants. Results demonstrate the dynamic cascades of child physiological regulation and parental provisions in shaping developmental outcome and may inform the construction of more targeted early interventions.

Four-month-old infants' long-term memory for a stressful social event

Infants clearly show an early capacity for memory for inanimate emotionally neutral events. However, their memory for social stress events has received far less attention. The aim of the study was to investigate infants' memory for a stressful social event (i.e., maternal unresponsiveness during the Still-Face paradigm) after a 15-day recall interval using changes in behavioral responses and salivary post-stress cortisol reactivity as measures of memory. Thirty-seven infants were exposed to social stress two times (experimental condition); the first time when they were 4 months of age and second exposure after a 2 week interval. Infants in the control condition (N = 37) were exposed to social stress just one time, at the age corresponding to the second exposure for infants in the experimental condition (4 months plus 2 weeks). Given individual differences in infants' reactivity to social stress events, we categorized infants as increasers or decreasers based on their cortisol reactivity after their initial exposure to the stress of the maternal still-face. Infants in the experimental condition, both increasers and decreasers, showed a significant change in cortisol response after the second exposure to the maternal still-face, though change was different for each reactivity group. In contrast, age-matched infants with no prior exposure to the maternal still-face showed similar post-stress cortisol reactivity to the reactivity of the experimental infants at their first exposure. There were no behavioral differences between increasers and decreasers during the Still-Face paradigm and exposures to the social stress. Thus differences between the experimental and control groups' post-stress cortisol reactivity was associated with the experimental group having previous experience with the social stress. These findings indicate long-term memory for social stress in infants as young as 4 months of age.

Infant video viewing and salivary cortisol responses: a randomized experiment

OBJECTIVE

To test the hypothesis that salivary cortisol levels respond differently when infants play with blocks compared with watching a digital video disk (DVD).

STUDY DESIGN

We conducted a randomized experiment in which 8- to 14-month-old infants either watched a DVD or played with blocks for 30 minutes. Serial salivary cortisol measurements were obtained and analyzed, and parental and infant responses and activities were recorded. Results were converted to standardized effect sizes (ESs) for clarity of presentation.

RESULTS

A total of 49 infants (49% female, mean age 10.6 months) participated in the study. In linear regression analyses, there was a trend toward higher cortisol levels in the block group at the 35-minute collection point (ES = 0.47, P = .08) and significantly higher levels at 45 minutes (ES = 0.56, P = .04); these salivary cortisol levels reflect serum levels approximately 10 and 20 minutes into the activity period, respectively. The results were substantially the same in sensitivity analyses excluding the outliers.

CONCLUSION

Viewing by infants of a DVD leads to different neuroendocrine responses than block play in a laboratory setting. The implications of these differences are currently unknown, but may suggest different means of cognitive engagement between interactive play and DVD viewing.

Diurnal cortisol rhythm and cognitive functioning in toddlers: the Generation R Study

Little is known about the relationship between diurnal cortisol secretion patterns and cognitive function early in life. This population-based study examined whether diurnal cortisol rhythms and cognitive functioning in toddlers are related. Within the Generation R Study, parents of 364 infants (median age: 14.2 months) collected saliva samples at five moments during one day. We assessed the diurnal cortisol rhythm by calculating the area under the curve (AUC), the cortisol awakening response (CAR), and the diurnal slope. Verbal cognitive functioning and fine motor development was determined at age 18 months. Nonverbal cognitive functioning was assessed at age 30 months. A more positive CAR was associated with a lower risk of delay in language comprehension (OR per 1-SD CAR: 0.62, 95%CI: 0.40-0.98, p = .04), a lower risk of nonoptimal fine motor development (OR per 1-SD slope: 0.74, 95%CI: 0.57-0.96, p = .03), and a lower risk of delay in nonverbal cognitive development (OR per 1-SD CAR: 0.58, 95%CI: 0.38-0.90, p = .02). Also, children with flatter slopes had a lower risk of delay in nonverbal cognitive development (OR per 1-SD slope: 0.51, 95%CI: 0.34-0.76, p = .001). Higher AUC levels were associated with a higher risk of delay in language production. These results show that variations in diurnal cortisol rhythms are already associated with variations in cognitive functioning at a young age. Infants with a diurnal cortisol pattern indicative of less stress and more cortisol reactivity, that is, lower AUC levels and a more positive CAR, show a lower risk of delay in cognitive functioning as toddlers.

Motor contingency learning and infants with Spina Bifida

Infants with Spina Bifida (SB) were compared to typically developing infants (TD) using a conjugate reinforcement paradigm at 6 months-of-age (n = 98) to evaluate learning, and retention of a sensory-motor contingency. Analyses evaluated infant arm-waving rates at baseline (wrist not tethered to mobile), during acquisition of the sensory-motor contingency (wrist tethered), and immediately after the acquisition phase and then after a delay (wrist not tethered), controlling for arm reaching ability, gestational age, and socioeconomic status. Although both groups responded to the contingency with increased arm-waving from baseline to acquisition, 15% to 29% fewer infants with SB than TD were found to learn the contingency depending on the criterion used to determine contingency learning. In addition, infants with SB who had learned the contingency had more difficulty retaining the contingency over time when sensory feedback was absent. The findings suggest that infants with SB do not learn motor contingencies as easily or at the same rate as TD infants, and are more likely to decrease motor responses when sensory feedback is absent. Results are discussed with reference to research on contingency learning in infants with and without neurodevelopmental disorders, and with reference to motor learning in school-age children with SB.

Neonatal pain in very preterm infants: long-term effects on brain, neurodevelopment and pain reactivity

Effects of early life psychosocial adversity have received a great deal of attention, such as maternal separation in experimental animal models and abuse/neglect in young humans. More recently, long-term effects of the physical stress of repetitive procedural pain have begun to be addressed in infants hospitalized in neonatal intensive care. Preterm infants are more sensitive to pain and stress, which cannot be distinguished in neonates. The focus of this review is clinical studies of long-term effects of repeated procedural pain-related stress in the neonatal intensive care unit (NICU) in relation to brain development, neurodevelopment, programming of stress systems, and later pain sensitivity in infants born very preterm (24-32 weeks' gestational age). Neonatal pain exposure has been quantified as the number of invasive and/or skin-breaking procedures during hospitalization in the NICU. Emerging studies provide convincing clinical evidence for an adverse impact of neonatal pain/stress in infants at a time of physiological immaturity, rapidly developing brain microstructure and networks, as well as programming of the hypothalamic-pituitary-adrenal axis. Currently it appears that early pain/stress may influence the developing brain and thereby neurodevelopment and stress-sensitive behaviors, particularly in the most immature neonates. However, there is no evidence for greater prevalence of pain syndromes compared to children and adults born healthy at full term. In addressing associations between pain/stress and outcomes, careful consideration of confounding clinical factors related to prematurity is essential. The need for pain management for humanitarian care is widely advocated. Non-pharmacological interventions to help parents reduce their infant's stress may be brain-protective.

Putting the concept of biological embedding in historical perspective

This paper describes evidence that led to the concept of biological embedding and research approaches designed to elucidates its mechanisms. Biological embedding occurs when experience gets under the skin and alters human biological and developmental processes; when systematic differences in experience in different social environments in society lead to systematically different biological and developmental states; when these differences are stable and long term; and, finally, when they have the capacity to influence health, well-being, learning, or behavior over the life course. Biological embedding emerged from insights in population health on the unique characteristics of socioeconomic gradients: Ubiquity in poor and postscarcity societies alike; gradient seen regardless of whether socioeconomic status is measured by income, education, or occupation; cutting widely across health, well-being, learning, and behavior outcomes; replicating itself on new conditions entering society; and, often, showing that flatter gradients mean better overall societal outcomes. Most important, the gradient begins the life course as a gradient in developmental health, suggesting that the emergence of a multifaceted resilience/vulnerability early in life is the best place to look for evidence of biological embedding. To understand its character, the metaphor of the "archeology of biological embedding" has been used, wherein the surficial stratum of the "dig" is experience and behavior, the shallow stratum is organ system and cellular function, and the deep stratum is gene function. We are now ready to address the fundamental question of biological embedding: How do early childhood environments work together with genetic variation and epigenetic regulation to generate gradients in health and human development across the life course?

Schore's regulation theory: maternal-infant interaction in the NICU as a mechanism for reducing the effects of allostatic load on neurodevelopment in premature infants

Premature infants confront numerous physiologic and environmental stressors in the neonatal intensive care unit (NICU) that have the potential to permanently alter their neurodevelopment. Schore's regulation theory postulates that positive maternal-infant interactions can shape the infant's developmental outcomes through inducing mechanistic changes in brain structure and function. The purposes of this article are to explain the regulation of infant neurobiological processes during interactions between mothers and healthy infants in the context of Schore's theory, to identify threats to these processes for premature infants, and to propose principles of clinical practice and areas of research necessary to establish a supportive environment and prevent or reduce maladaptive consequences for these vulnerable infants. A premature birth results in the disruption of neurodevelopment at a critical time. Chronic exposure to stressors related to the NICU environment overwhelms immature physiologic and stress systems, resulting in significant allostatic load, as measured by long-term neurodevelopmental impairments in the premature infant. Positive maternal-infant interactions during NICU hospitalization and beyond have the potential to reduce neurologic deficits and maximize positive neurodevelopmental outcomes in premature infants. The quality of the maternal-infant interaction is affected not only by the infant's developing neurobiology but also by the mother's responses to the stressors surrounding a premature birth and mothering an infant in the NICU environment. Nurses can empower mothers to overcome these stressors, promote sensitive interactions with their infants, and facilitate neurodevelopment. Research is critically needed to develop and test nursing interventions directed at assisting mothers in supporting optimal neurodevelopment for their infants.

Motor learning and working memory in children born preterm: a systematic review

Children born preterm have a higher risk for developing motor, cognitive, and behavioral problems. Motor problems can occur in combination with working memory problems, and working memory is important for explicit learning of motor skills. The relation between motor learning and working memory has never been reviewed. The goal of this review was to provide an overview of motor learning, visual working memory and the role of working memory on motor learning in preterm children. A systematic review conducted in four databases identified 38 relevant articles, which were evaluated for methodological quality. Only 4 of 38 articles discussed motor learning in preterm children. Thirty-four studies reported on visual working memory; preterm birth affected performance on visual working memory tests. Information regarding motor learning and the role of working memory on the different components of motor learning was not available. Future research should address this issue. Insight in the relation between motor learning and visual working memory may contribute to the development of evidence based intervention programs for children born preterm.

Mental health concerns of the premature infant through the lifespan

Because of increased survival rates, neurodevelopmental issues, chronic medical problems, and sometimes complex family issues involved with prematurity, mental health clinicians commonly assess preterm clients and manage their behavioral and mental health problems. Understanding prematurity survival and neurodevelopmental outcomes is important for contextualizing the mental health problems seen in this high-risk population. This article provides a brief overview of prematurity outcomes in the domains of prematurity relevant to practicing child psychiatrists. Prematurity is also examined as it relates to parental mental health challenges, infant mental health outcomes, high frequency attention problems, and psychiatric disorders. The complex interactions between prematurity and family well-being are also highlighted. Finally, evidence-based treatment modalities involved in prevention and management are explored.

A preliminary study of cortisol reactivity and behavior problems in young children born premature

The purpose of the present study was to examine the relation between cortisol reactivity and comorbid internalizing and externalizing behavior problems among children born premature. Children between the ages of 18 and 60 months who were born <37 weeks gestation and presented with clinically significant externalizing behavior problems were included. Children were categorized based on those who mounted a cortisol response to a stressor and those who did not mount a cortisol response. Children demonstrating the cortisol response were reported to have more problems with attention, emotional reactivity, anxiety, and depression based on maternal report and displayed higher rates of negative verbalizations during a mother-child interaction than children without a cortisol response. These results extend the findings of the relation between cortisol reactivity and comorbid internalizing and externalizing behavior problems to a sample of children born premature.

Infant anticipatory stress

In humans, anticipatory stress involves activation of the limbic-hypothalamic-pituitary-adrenal axis, which releases stress hormones such as cortisol in response to an impending stressor. Conditioning of the stress response to anticipate and prepare for future challenges is a hallmark of adaptation. It is unknown whether human infants in the first year of life have developed the neural circuitry to support the anticipation of stressful events in an attachment context. Here, we show that human infants at six months of age produce an anticipatory stress response, as indicated by the release of stress hormones, when re-exposed after 24 h to a context in which they demonstrated a stress response to a disruption in the parent-infant relationship. Although infant stress response (cortisol elevation) was greater to the stressful event (parent unresponsiveness) than to the second exposure to the stress context (room, chair, presence of parent and experimenter, etc.), it was greater in the stress group than in the control group on both days. Results suggest that human infants have the capacity to produce an anticipatory stress response that is based on expectations about how their parents will treat them in a specific context.

Cortisol levels in relation to maternal interaction and child internalizing behavior in preterm and full-term children at 18 months corrected age

Cortisol levels were compared in children born preterm at extremely low gestational age (ELGA; 24-28 weeks), very low gestational age (VGLA; 29-32 weeks), and full-term in response to cognitive assessment at 18 months corrected age (CA). Further, we investigated the relationship between maternal interactive behaviors and child internalizing behaviors (rated by the mother) in relation to child cortisol levels. EGLA children had higher "pretest" cortisol levels and a different pattern of cortisol response to cognitive assessment compared to VGLA and full-terms. Higher cortisol levels in ELGA, but not full-term, children were associated with less optimal mother interactive behavior. Moreover, the pattern of cortisol change was related to internalizing behaviors among ELGA, and to a lesser degree VLGA children. In conclusion, our findings suggest altered programming of the hypothalamic-pituitary-adrenal (HPA) axis in preterm children, as well as their greater sensitivity to environmental context such as maternal interactive behavior.

How experience gets under the skin to create gradients in developmental health

Social environments and experiences get under the skin early in life in ways that affect the course of human development. Because most factors associated with early child development are a function of socio-economic status, differences in early child development form a socio-economic gradient. We are now learning how, when, and by what means early experiences influence key biological systems over the long term to produce gradients: a process known as biological embedding. Opportunities for biological embedding are tethered closely to sensitive periods in the development of neural circuitry. Epigenetic regulation is the best example of operating principles relevant to biological embedding. We are now in a position to ask how early childhood environments work together with genetic variation and epigenetic regulation to generate socially partitioned developmental trajectories with impact on health across the life course.

Physiological correlates of memory recall in infancy: vagal tone, cortisol, and imitation in preterm and full-term infants at 6 months

We examined the role of physiological regulation (heart rate, vagal tone, and salivary cortisol) in short-term memory in preterm and full-term 6-month-old infants. Using a deferred imitation task to evaluate social learning and memory recall, an experimenter modeled three novel behaviors (removing, shaking, and replacing a glove) on a puppet. Infants were tested immediately after being shown the behaviors as well as following a 10-min delay. We found that greater suppression of vagal tone was related to better memory recall in full-term infants tested immediately after the demonstration as well as in preterm infants tested later after a 10-min delay. We also found that preterm infants showed greater coordination of physiology (i.e., tighter coupling of vagal tone, heart rate, and cortisol) at rest and during retrieval than full-term infants. These findings provide new evidence of the important links between changes in autonomic activity and memory recall in infancy. They also raise the intriguing possibility that social learning, imitation behavior, and the formation of new memories are modulated by autonomic activity that is coordinated differently in preterm and full-term infants.

Mental health concerns of the premature infant through the lifespan

Because of increased survival rates, neurodevelopmental issues, chronic medical problems, and sometimes complex family issues involved with prematurity, mental health clinicians commonly assess preterm clients and manage their behavioral and mental health problems. Understanding prematurity survival and neurodevelopmental outcomes is important for contextualizing the mental health problems seen in this high-risk population. This article provides a brief overview of prematurity outcomes in the domains of prematurity relevant to practicing child psychiatrists. Prematurity is also examined as it relates to parental mental health challenges, infant mental health outcomes, high frequency attention problems, and psychiatric disorders. The complex interactions between prematurity and family well-being are also highlighted. Finally, evidence-based treatment modalities involved in prevention and management are explored.

Hair cortisol predicts object permanence performance in infant rhesus macaques (Macaca mulatta)

Although high circulating levels of glucocorticoids are associated with impaired cognitive performance in adults, less is known about this relationship in infancy. Furthermore, because studies have relied on acute cortisol measures in blood plasma or saliva, interpretation of the results may be difficult as acute measures may in part reflect emotional responses to testing procedures. In this study we examined whether hair cortisol, an integrated measure of hypothalamic-pituitary-adrenal (HPA) axis functioning, predicted performance of nursery-reared (NR) infant rhesus monkeys (n = 32) on Piagetian object permanence tasks. Testing of NR infants began at 19.8 +/- 2.2 (mean +/- SE) days of age and continued for the next several months. Hair cortisol concentrations from the 32 NR monkeys were compared to those of 20 mother-peer-reared (MPR) infants. Hair was shaved at Day 14, allowed to regrow, and obtained again at month 6, thus representing integrated cortisol over a 5.5-month period of time. NR and MPR infants did not differ in month 6 hair cortisol values (t((50)) = 0.02, p = 0.98). Linear regression revealed that hair cortisol predicted object permanence performance in the NR infants. Infants with higher hair cortisol reached criterion at later ages on the well (p < 0.01), screen (p < 0.05), and A-not-B (p < 0.05) tasks and required more test sessions to complete the well (p < 0.01) and screen tasks (p < 0.05). These data are the first to implicate hair cortisol as a reliable predictor of early cognitive performance in infant macaque monkeys.

Effects of intrauterine exposure to synthetic glucocorticoids on fetal, newborn, and infant hypothalamic-pituitary-adrenal axis function in humans: a systematic review

BACKGROUND

Synthetic glucocorticoids are commonly used in reproductive medicine. Fetal organ systems are highly sensitive to changes in the intrauterine environment, including overexposure to glucocorticoids. Structural and functional alterations resulting from such changes may persist throughout life and have been associated with diverse diseases. One system that could be particularly sensitive to fetal glucocorticoid overexposure is the hypothalamic-pituitary-adrenal (hpa) axis. Many human studies have investigated this possibility, but a systematic review to identify consistent, emergent findings is lacking.

METHODS

We systematically review 49 human studies, assessing the effects of intrauterine exposure to synthetic glucocorticoids on fetal, neonate, and infant hpa function.

RESULTS

Study quality varied considerably, but the main findings held true after restricting the analyses to higher-quality studies: intrauterine exposure to synthetic glucocorticoids reduces offspring hpa activity under unstimulated conditions after pain but not pharmacological challenge. Although reduced unstimulated hpa function appears to recover within the first 2 wk postpartum, blunted hpa reactivity to pain is likely to persist throughout the first 4 months of life. There is some evidence that the magnitude of the effects is correlated with the total amount of glucocorticoids administered and varies with the time interval between glucocorticoid exposure and hpa assessment.

CONCLUSIONS

This systematic review has allowed the demonstration of the way in which intrauterine exposure to various regimens of synthetic glucocorticoids affects various forms of hpa function. As such, it guides future studies in terms of which variables need to be focused on in order to further strengthen the understanding of such therapy, whilst continuing to profit from its clinical benefits.

Cortisol Reactivity, Maternal Sensitivity, and Infant Preference for Mother's Familiar Face and Rhyme in 6-Month-Old Infants

This study investigated how cortisol (stress) reactivity and mothers' behavioral sensitivity affect familiarity preferences in 6-month-old infants. Relations between sensitivity and stress were explored using saliva samples taken from mothers and infants before, and 20-min after, two preferential looking experiments. Photographs and voice recordings from infants' mothers were incorporated into standard visual preference tasks. Sensitivity was assessed by determining the degree of behavioral synchrony between mother and infant from a 10-min interaction period preceding the preferential looking experiments. Results showed that decreasing infant cortisol reactivity and greater maternal sensitivity were associated with familiarity preferences for mother's face stimuli. For the experiment with voice stimuli, a sex difference was obtained in the relationship between the directionality of cortisol reactivity and familiarity preferences. Results are related to a parallel study with 3-month-old infants (Thompson & Trevathan, 2008), and issues are discussed in terms of infants' developing emotional independence from mother.

The association between prenatal exposure to cigarettes and cortisol reactivity and regulation in 7-month-old infants

We examined the association between prenatal exposure to cigarettes and adrenocortical responses to stress in 7-month-old infants. Cortisol levels were assessed twice prior to and twice following affect-eliciting procedures in 111 (59 exposed and 52 nonexposed) infants. Cortisol reactivity was defined as the difference between the peak poststressor cortisol level and the pretask cortisol level. Higher values indicated higher cortisol reactivity. Exposed infants had higher peak cortisol reactivity than nonexposed infants. There were no differences in pretask cortisol levels. Maternal hostility mediated the association between cigarette exposure and peak cortisol reactivity. Furthermore, infant gender moderated this association such that exposed boys had significantly higher peak cortisol reactivity than nonexposed infants or exposed girls. These findings provide additional evidence that prenatal cigarette exposure is associated with dysregulation during infancy and that early adverse, nonsocial experiences may have relatively long-lasting effects on cortisol reactivity in infants.

Contingency Learning and Reactivity in Preterm and Full-Term Infants at 3 Months

Learning difficulties in preterm infants are thought to reflect impairment in arousal regulation. We examined relationships among gestational age, learning speed, and behavioral and physiological reactivity in 55 preterm and 49 full-term infants during baseline, contingency, and nonreinforcement phases of a conjugate mobile paradigm at 3 months corrected age. For all infants, negative affect, looking duration, and heart rate levels increased during contingency and nonreinforcement phases, whereas respiratory sinus arrhythmia (RSA, an index of parasympathetic activity) decreased and cortisol did not change. Learners showed greater RSA suppression and less negative affect than nonlearners. This pattern was particularly evident in the preterm group. Overall, preterm infants showed less learning, spent less time looking at the mobile, and had lower cortisol levels than full-term infants. Preterm infants also showed greater heart rate responses to contingency and dampened heart rate responses to nonreinforcement compared to full-term infants. Findings underscore differences in basal and reactivity measures in preterm compared to full-term infants and suggest that the capacity to regulate parasympathetic activity during a challenge enhances learning in preterm infants.

Developmental origins theory from prematurity to adult disease

Developmental Origins Theory has received little coverage in the nursing literature, even though it has received much attention in other sciences. The theory proposes that prenatal stress provokes adaptive changes in endocrine and metabolic processes that become permanently programmed and impact later adult health. This paper reviews the theory and describes the primary neuroendocrine mechanism of hypothalamic-pituitary-adrenal axis function. Supporting research evidence in preterm infant and adult samples is presented. Through knowledge of the theory and the long-term sequelae for preterm infants, nurses will have a different theoretical perspective and growing evidence to consider in their care for pregnant women and infants.

Cognitive development and cortisol patterns in mid-life: findings from a British birth cohort

Life-course associations among cortisol, cognitive development and educational attainment in the general population are not well understood. Using the 1958 British birth cohort, our aim was to establish whether cortisol patterns at age 45y are associated with childhood cognition and qualification level by adulthood. We measured salivary cortisol in 6527 individuals, 45min after waking (t(1)) and 3h later (t(2)). To identify lack of morning cortisol peak and diurnal rhythm, we defined groups with: (a) t(1) cortisol in the bottom 5% of the distribution, or (b) 'flat't(1)-t(2) cortisol. Data on cognitive tests at ages 7, 11 and 16y and educational level were used. All childhood cognitive tests (maths, reading, verbal and non-verbal ability) were inversely associated, although not always significantly, with low t(1) and flat t(1)-t(2) cortisol. For example, at age 11 for males, a standard deviation (SD) increase in maths score was associated with a 28% decreased odds for lowest t(1) cortisol, and with a 13% decreased odds of flat t(1)-t(2) cortisol. Associations for lowest t(1) and flat t(1)-t(2) cortisol were attenuated after adjustment for qualification level at 33y among males, although adjustment for childhood socio-economic position had little effect. Weaker associations for lowest t(1) cortisol among females were either unchanged or strengthened after adjustment for qualification level. Our results for males, but less so for females, are compatible with a causal relationship in either direction, namely from cortisol to cognitive ability or vice versa.

Comparisons between salivary cortisol levels in six-months-olds and their parents

BACKGROUND

There is a close relation between the psychosocial environment of the infant--including the perception of maternal behaviour--and cortisol levels of the infant. One previous study has also demonstrated a correlation between mother and infant mean cortisol levels. In this study, this relation was further explored, also including father cortisol levels.

METHODS

Saliva cortisol samples were collected from 51 six-months-olds and their parents on the same day in the morning, afternoon and evening. Analyses were performed with a radioimmunoassay technique. All mothers were at home with their child at this age and 47/51 mothers were breast feeding.

RESULTS

Strong correlations were found between mother and child levels on all sampling occasions whereas weaker correlations were found between father and child levels and only in the afternoon and the evening samples. There was also a strong relation between waking up/bedtime-difference in mother and child and a weaker relation between the corresponding measure in father and child.

CONCLUSIONS

The stronger mother-infant than father-infant cortisol level correlations probably mirror that mother and infant not only have genetic similarities but also have been exposed to similar environmental conditions to a higher degree than father and infant.