Executive functions in preschool children born preterm: application of cognitive neuroscience paradigms

Biological and environmental factors may affect children's executive function through motor and sensorimotor development: Preterm birth and cerebral palsy

Disruptive biological and environmental factors may undermine the development of children's motor and sensorimotor skills. Since the development of cognitive skills, including executive function, is grounded in early motor and sensorimotor experiences, early delays or impairments in motor and sensorimotor processing often trigger dynamic developmental cascades that lead to suboptimal executive function outcomes. The purpose of this perspective paper is to link early differences in motor/sensorimotor processing to the development of executive function in children born preterm or with cerebral palsy. Uncovering such links in clinical populations would improve our understanding of developmental pathways and key motor and sensorimotor skills that are antecedent and foundational for the development of executive function. This knowledge will allow the refinement of early interventions targeting motor and sensorimotor skills with the goal of proactively improving executive function outcomes in at-risk populations.

Development of cool and hot executive function deficit in children born very low birth weight with normal early development: A longitudinal cohort from aged 6 to 10

BACKGROUND

Studies showed preterm children born with very low birth weight (VLBW, <1500 g) are at risk for poorer executive functions (EFs). However, very little research has been reported longitudinally on the development of both cool and hot EFs deficits in preschool to school-age VLBW preterm children with normal early development.

AIMS

Present study aimed to investigate the development of cool and hot EFs in VLWB preterm children longitudinally.

METHODS

Forty preterm children born VLBW were followed up at ages 6, 8, and 10. Fifty term-born controls were recruited at each age stage. Cool EFs was assessed using backward digit span subtest of WISC-IV, Knox's Cube Test, Comprehensive Non-verbal Attention Test Battery (CNAT), Tower of London (ToL), Wisconsin Card Sorting Test (WCST), and hot EFs was assessed using Theory of Mind (ToM) and Delay of Gratification (GIFT) tasks.

RESULTS

The six-year-old VLBW preterm group showed significantly lower scores of planning in ToL, inhibition control in CNAT, and in both ToM and GIFT tasks. There is no significant difference in average cool and hot EFs between the eight and ten-year-old preterm group and the control group.

CONCLUSIONS

At six, VLBW preterm infants with normal early development have delayed cool and hot EFs development. Although the average performance of EFs can reach the level of the control group with age increasing to eight and ten years, there are still individual differences. It is recommended that more complete development indicators be established in the future, and early intervention should be made for VLBW premature children with delayed EFs.

Therapeutic Interventions in Rat Models of Preterm Hypoxic Ischemic Injury: Effects of Hypothermia, Caffeine, and the Influence of Sex

Infants born prematurely have an increased risk of experiencing brain injury, specifically injury caused by Hypoxia Ischemia (HI). There is no approved treatment for preterm infants, in contrast to term infants that experience Hypoxic Ischemic Encephalopathy (HIE) and can be treated with hypothermia. Given this increased risk and lack of approved treatment, it is imperative to explore and model potential treatments in animal models of preterm injury. Hypothermia is one potential treatment, though cooling to current clinical standards has been found to be detrimental for preterm infants. However, mild hypothermia may prove useful. Caffeine is another treatment that is already used in preterm infants to treat apnea of prematurity, and has shown neuroprotective effects. Both of these treatments show sex differences in behavioral outcomes and neuroprotective effects, which are critical to explore when working to translate from animal to human. The effects and research history of hypothermia, caffeine and how sex affects these treatment outcomes will be explored further in this review article.

A randomized EPIREMED protocol study on the long-term visuo spatial effects of very preterm children with a working memory deficit

BACKGROUND

Very preterm children generally perform poorly in executive functions and particularly in working memory. Adaptive training tasks encouraging these children to work continuously on their personal working memory capacity can be very useful. Above all in preschool-age children, several cognitive training programs focused on improving working memory capacity. Cogmed is a computerized visuospatial cognitive training program that improves working memory in children and adolescents with attention-deficit/hyperactivity disorder. The main objective is to assess the long-term effects (18 months) of cognitive training (Cogmed) on visuospatial processing in preschool-age very preterm children with working memory impairment.

METHODS

The EPIREMED study is a prospective, randomized, controlled, multicentric trial nested in a population based epidemiological survey. An intervention group (Cogmed cognitive training) and a control group (standard care management) will compare children aged 5½ to 6 years, born between 24- and 34-weeks' gestational age, with a global intelligence quotient > 70 and a working memory index < 85. The study will include 166 children from national study EPIPAGE-2 (Epidemiological Study on Small Gestational Ages). The intervention consists of 25 sessions administered over a 5- to 8-week period. The primary endpoint will be the visuospatial processing, assessed by the score of the visuospatial index: score of the WPPSI-IV (Wechsler Preschool and Primary Scale of Intelligence). The secondary endpoints will allow to assess the executive functions, language and abilities, infant behavior, quality of life assessment, school performance and parental anxiety.

DISCUSSION

This project's primary goal is to demonstrate the necessity of early visuospatial memory assessment within the vulnerable population of very preterm children, and to prove the feasibility and efficacy of computerized cognitive training using online software programs. A better global neuropsychological development improvement (visuospatial processing and other far transfer) can be expected with an improvement in learning and decreased behavioral problems. In the long term, these improvements might also reduce those global costs linked to the consequences of extreme prematurity.

TRIAL REGISTRATION

NCT02757794 (registered on 2nd May 2016 at ClinicalTrial.gov).

Altered orbitofrontal activation in preterm-born young adolescents during performance of a reality filtering task

Preterm birth is one of the main causes for neurodevelopmental problems, and has been associated with a wide range of impairments in cognitive functions including executive functions and memory. One of the factors contributing to these adverse outcomes is the intrinsic vulnerability of the premature brain. Neuroimaging studies have highlighted structural and functional alterations in several brain regions in preterm individuals across lifetime. The orbitofrontal cortex (OFC) is crucial for a multitude of complex and adaptive behaviours, and its structure is particularly affected by premature birth. Nevertheless, studies on the functional impact of prematurity on the OFC are still missing. Orbitofrontal Reality filtering (ORFi) refers to the ability to distinguish if a thought is relevant to present reality or not. It can be tested using a continuous recognition task and is mediated by the OFC in adults and typically developing young adolescents. Therefore, the ORFi task was used to investigate whether OFC functioning is affected by prematurity. We compared the neural correlates of ORFi in 35 young adolescents born preterm (below 32 weeks of gestation) and aged 10 to 14 years with 25 full term-born controls. Our findings indicate that OFC activation was required only in the full-term group, whereas preterm young adolescents did not involve OFC in processing the ORFi task, despite being able to correctly perform it.

Development of visuospatial memory in preterm infants: A new paradigm to assess short-term and working memory

Preterm infants have a higher risk of showing visuospatial memory impairment, the function that allows to encode and remember visual and spatial information. It has been studied in late childhood in preterm children. Studies on visuospatial memory throughout the first 2 years of life are still scarce. Behavior, temperament, and overall cognition could be altered in preterm children affecting memory performance. Therefore, the main aim of this study was to evaluate short-term and visuospatial working memory performance in a preterm sample followed longitudinally at 12, 15, 18, and 22 months (N = 15), and compare their performance with that of full-term children (N = 65). The secondary aim was to analyze the course of mnesic development in preterm infants and relate their memory performance to other cognitive abilities and behavioral tendencies. Assessment included previously published tasks and an experimental paradigm. Results showed that preterm children scored lower than full-term children on visuospatial short-term and working memory at 12 and 22 months of age, although these results varied depending on the memory test used. Preterm children's memory results showed that these skills improve in this population between the first and second year of life. Finally, memory performance was directly associated with the level of cognitive development and the presence of proactive behaviors, while being inversely correlated with the presence of disruptive behaviors and a difficult temperamental style. These preliminary findings suggest that it is possible to detect visuospatial memory difficulties in the preterm population before the age of two.

Prematuridade, Funções Executivas e Qualidade dos Cuidados Parentais: Revisão Sistemática de Literatura

RESUMO Este artigo de revisão visa contextualizar o desenvolvimento das funções executivas (FE) em crianças prematuras, com especial atenção para o efeito dos cuidados parentais. As principais bases eletrônicas foram utilizadas para essa revisão: 31 estudos originais, duas meta-análises, uma meta-síntese e dois artigos de revisão foram identificados. Concluiu-se que as crianças prematuras têm maior risco de disfunção executiva global, sendo a qualidade dos cuidados parentais fundamentais para a modulação das FE, nomeadamente no que concerne às variáveis socioemocionais da interação, como a sensibilidadematerna. Salientam-se ainda as principais limitações dos estudos analisados e apontam-se recomendações para futura investigação sobre os efeitos dos cuidados parentais no desenvolvimento de FE em crianças prematuras.

Longitudinal associations between self-regulation and the academic and behavioral adjustment of young children born preterm

Much of the research to date about the structure of self-regulation in early childhood has been conducted with low medical risk samples, with the general conclusion that self-regulation can be separated into overlapping executive function and effortful control factors that differentially predict child outcomes. We examined the factor structure of 36-month self-regulation among children born prematurely (n = 168) and the extent to which self-regulation predicted maternal ratings of children's socioemotional and academic competence when they were six years of age. Statistical analyses revealed a single self-regulation factor for this high neonatal risk sample, and this self-regulation factor mediated associations between early sociodemographic risk and mothers' ratings of academic competence and externalizing problems. Our findings suggest that early intervention research with children born preterm should focus on promoting supportive early environments, particularly parental sensitivity to infant cues.

Executive functioning of Portuguese preschoolers in the Shape School test: A cross cultural study

The Shape School is a neuropsychological test of executive functions (EF) for preschool-aged children. The purposes of this study were: (a) to adapt the use of the Shape School for European Portuguese preschool children and (b) to examine the cultural sensitivity of this test comparing the performance of Portuguese sample and U.S. normative sample. The executive functioning of 233 typically developing children aged 3 to 5 years old (M = 57.52; SD = 10.25; in months) was analyzed and according to our results, the adapted version was appropriate to obtain the discrimination among age-groups. Portuguese and American preschoolers show similar EF profiles. It was possible, in both samples, to note the sensitivity of the measurement to age-related differences, with the older age groups outperforming the younger. Therefore, the Portuguese version of the Shape School was considered suitable for research and clinical purposes.

Examining an Executive Function Battery for Use with Preschool Children with Disabilities

Performance-based assessments of EF for use with young children who have or are at risk for disabilities are lacking. The current study investigates the use of a computerized battery for children with subclinical behaviors (N = 846) across a variety of developmental disabilities and evaluates practical information about feasibility of task administration. Results reveal that children with disabilities performed similarly to their typically developing peers across a variety of metrics for evaluating the battery, ranging from percent correct scores to administrator quality ratings. Thus, the battery may be considered an easy-to-administer, performance-based assessment tool in which children with disabilities do not perform systemically worse than typically developing peers.

Executive function in children born preterm: Risk factors and implications for outcome

Executive function (EF) refers to the set of cognitive processes involved in the self-regulation of emotion and goal-directed behavior. These skills and the brain systems that support them develop throughout childhood and are frequently compromised in preterm children, even in those with broadly average global cognitive ability. Risks for deficits in EF in preterm children and attendant problems in learning and psychosocial functioning are higher in those with more extreme prematurity, neonatal complications, and related brain abnormalities. Associations of higher levels of EF with more supportive home and school environments suggest a potential for attenuating these risks, especially with early identification. Further research is needed to understand how deficits in EF evolve in preterm children, refine assessment methods, and develop interventions that either promote the development of EF in this population or help children to compensate for these weaknesses.

Neural Correlates of Reward Processing in Typical and Atypical Development

Atypically developing children including those born preterm or who have autism spectrum disorder can display difficulties with evaluating rewarding stimuli, which may result from impaired maturation of reward and cognitive control brain regions. During functional magnetic resonance imaging, 58 typically and atypically developing children (6-12 years) participated in a set-shifting task that included the presentation of monetary reward stimuli. In typically developing children, reward stimuli were associated with age-related increases in activation in cognitive control centers, with weaker changes in reward regions. In atypically developing children, no age-related changes were evident. Maturational disturbances in the frontostriatal regions during atypical development may underlie task-based differences in activation.

The relevance of the irrelevant: Attention and task-set adaptation in prematurely born adults

OBJECTIVE

To investigate attention and task-set adaptation in a preterm born very low birth weight (PT/VLBW) population by means of event-related potential components from an adapted cued go/no-go task.

METHODS

P3 components after target and non-target cues, as well as target, no-go and non-target imperative stimuli were compared in 30 PT/VLBW young adults and 33 term-born controls. Changes in P3 amplitudes as a function of time-on-task were also investigated.

RESULTS

The PT/VLBW group had larger P3 amplitudes to non-target cues and non-targets compared with controls. There were no significant group differences in the P3s to target or no-go stimuli. Moreover, the amplitude of the P3 to non-target cues and non-targets decreased significantly over time in the control group but not in the PT/VLBW group.

CONCLUSIONS

PT/VLBW young adults allocate more attention to behaviorally irrelevant information than term-born controls, and persist in attending to this information over time.

SIGNIFICANCE

This is the first study to investigate ERP components in an adult population born preterm with very low birth weight.

Effects of age, experience and inter-alpha inhibitor proteins on working memory and neuronal plasticity after neonatal hypoxia-ischemia

Neonatal cerebral hypoxia-ischemia (HI) commonly results in cognitive and sensory impairments. Early behavioral experience has been suggested to improve cognitive and sensory outcomes in children and animal models with perinatal neuropathology. In parallel, we previously showed that treatment with immunomodulator Inter-alpha Inhibitor Proteins (IAIPs) improves cellular and behavioral outcomes in neonatal HI injured rats. The purpose of the current study was to evaluate the influences of early experience and typical maturation in combination with IAIPs treatment on spatial working and reference memory after neonatal HI injury. A second aim was to determine the effects of these variables on hippocampal CA1 neuronal morphology. Subjects were divided into two groups that differed with respect to the time when exposed to eight arm radial water maze testing: Group one was tested as juveniles (early experience, Postnatal day (P) 36-61) and adults (P88-113), and Group two was tested in adulthood only (P88-113; without early experience). Three treatment conditions were included in each experience group (HI+Vehicle, HI+IAIPs, and Sham subjects). Incorrect arm entries (errors) were compared between treatment and experience groups across three error types (reference memory (RM), working memory incorrect (WMI), working memory correct (WMC)). Early experience led to improved working memory performance regardless of treatment. Combining IAIPs intervention with early experience provided a long-term behavioral advantage on the WMI component of the task in HI animals. Anatomically, early experience led to a decrease in the average number of basal dendrites per CA1 pyramidal neuron for IAIP treated subjects and a significant reduction in basal dendritic length in control subjects, highlighting the importance of pruning in typical early life learning. Our results support the hypothesis that early behavioral experience combined with IAIPs improve outcome on a relativity demanding cognitive task, beyond that of a single intervention strategy, and appears to facilitate neuronal plasticity following neonatal brain injury.

Neonatal morphine exposure in very preterm infants-cerebral development and outcomes

OBJECTIVE

To investigate the association of morphine exposure in very preterm infants with cerebral volumes and neurodevelopmental outcome from birth through middle childhood.

STUDY DESIGN

Observational study of very preterm infants in the Victorian Infant Brain Study cohort. A total of 230 infants born <30 weeks' gestational age or <1250 g were recruited from all admissions to the neonatal intensive care unit of the Royal Women's Hospital. Fifty-seven (25%) infants received morphine analgesia during their neonatal intensive care unit stay at the attending physician's discretion. Primary outcomes were regional brain volumes at term and 7 years; neurobehavioral performance at term; and cognitive, motor, emotional, behavioral, communication, and executive function scores at age 2 and 7 years. Linear regressions were used to compare outcomes between participants who did and did not receive morphine.

RESULTS

At term, preterm infants who received morphine had similar rates of gray matter injury to no-morphine infants, but a trend toward smaller cortical volumes in the orbitofrontal (Pleft=.002, Pright=.01) and subgenual (Pleft=.01) regions. At 7 years, cortical volumes did not differ between groups. At 2 years, morphine-exposed children were more likely to show behavioral dysregulation (P=.007) than no-morphine children, but at 7 years no detrimental impacts of morphine on neurobehavioral outcome were observed.

CONCLUSIONS

Low-dose morphine analgesia received during neonatal intensive care was associated with early alterations in cerebral structure and short-term neurobehavioral problems that did not persist into childhood.

Hot executive function following moderate-to-late preterm birth: altered delay discounting at 4 years of age

Interest in monitoring long-term neurodevelopmental outcomes of children born moderate-to-late preterm (32-36 weeks gestation) is increasing. Moderate-to-late preterm birth has a negative impact on academic achievement, which may relate to differential development of executive function (EF). Prior studies reporting deficits in EF in preterm children have almost exclusively assessed EF in affectively neutral contexts in high-risk preterm children (< 32 weeks gestation). Disrupted function in motivational or emotionally charged contexts (hot EF) following preterm birth remains uninvestigated, despite evidence that preterm children show differential development of neural circuitry subserving hot EF, including reduced orbitofrontal cortex volume. The present study is the first to examine whether low-risk, healthy children born moderate-to-late preterm exhibit impairments in the development of hot EF. Preterm children at age 4.5 years were less likely to choose larger, delayed rewards across all levels of reward magnitude on a delay discounting task using tangible rewards, but performed more similarly to their full-term peers on a delay aversion task involving abstract rewards and on measures of cool EF. The relationship between gestational age at birth and selection of delayed rewards extended across the entire gestational age range of the sample (32-42 weeks), and remained significant after controlling for intelligence and processing speed. Results imply that there is not a finite cut-off point at which children are spared from potential long-term neurodevelopmental effects of PT birth. Further investigation of reward processing and hot EF in individuals with a history of PT birth is warranted given the susceptibility of prefrontal cortex development to early environmental variations.

Socioeconomic status and executive function: developmental trajectories and mediation

Childhood socioeconomic status (SES) predicts executive function (EF), but fundamental aspects of this relation remain unknown: the developmental course of the SES disparity, its continued sensitivity to SES changes during that course, and the features of childhood experience responsible for the SES-EF relation. Regarding course, early disparities would be expected to grow during development if caused by accumulating stressors at a given constant level of SES. Alternatively, they would narrow if schooling partly compensates for the effects of earlier deprivation, allowing lower-SES children to 'catch up'. The potential for later childhood SES change to affect EF is also unknown. Regarding mediating factors, previous analyses produced mixed answers, possibly due to correlation amongst candidate mediators. We address these issues with measures of SES, working memory and planning, along with multiple candidate mediators, from the NICHD Study of Early Childcare (n = 1009). Early family income-to-needs and maternal education predicted planning by first grade, and income-to-needs predicted working memory performance at 54 months. Effects of early SES remained consistent through middle childhood, indicating that the relation between early indicators of SES and EF emerges in childhood and persists without narrowing or widening across early and middle childhood. Changes in family income-to-needs were associated with significant changes in planning and trend-level changes in working memory. Mediation analyses supported the role of early childhood home characteristics in explaining the association between SES and EF, while early childhood maternal sensitivity was specifically implicated in the association between maternal education and planning. Early emerging and persistent SES-related differences in EF, partially explained by characteristics of the home and family environment, are thus a potential source of socioeconomic disparities in achievement and health across development.

Relation of perinatal risk and early parenting to executive control at the transition to school

Executive control (EC) develops rapidly during the preschool years and is central to academic achievement and functional outcome. Although children with perinatal adversity are at known risk for EC impairments, little is known about the underlying nature of these impairments or the mechanisms that contribute to their development over time. Drawing on a cohort of 110 high-risk children born very preterm (VPT; < 33 weeks / < 1500 g) and 113 healthy full-term children, this study examined the implications of perinatal adversity and early parenting for children's EC as they transitioned to formal schooling. Parent supportive presence, intrusiveness, and parent-child synchrony were observed during a series of problem-solving tasks at ages 2 and 4 years. At age 6, children completed a comprehensive battery of EC tasks. Academic outcomes were assessed at age 9. The VPT group showed global EC impairments at age 6, although the unitary factor that best characterized the structure of EC was the same in both groups. High-risk dyads were characterized by more intrusive and less synchronous parent-child interactions in early childhood, which in turn predicted poorer child EC at age 6. EC partially mediated the relation of risk status to poorer academic achievement at age 9. Findings demonstrate the cumulative effects of perinatal adversity on children's EC in the crucial transition to schooling. They also highlight the importance of the parent-child relationship as a target for intervention efforts to help mitigate these effects.

[Development of executive functions in preterm children]

The rate of children born prematurely has increased considerably in the last few decades, and their developmental outcome remains of great concern. The literature on the impact of prematurity has reported a wide range of cognitive and behavioral problems that may be related to deficits in executive function (EF) skills. EF refers to a series of high-level processes (selective attention, inhibition, set shifting, working memory, planning, goal setting) that develop throughout childhood and adolescence and play an important role in cognitive and social development as well as in school achievement. EF skills have been linked to the prefrontal cortex, as well as to other neural networks and brain regions including the basal ganglia and cerebellum. This paper focuses on studies related to the development of EF and social behavior in children born preterm. The preschool period is a critical time to perform neuropsychological assessment in addition to IQ testing, and to detect the child's specific needs in order to adapt effective intervention to enhance the development of executive processes in these high-risk children.

Complementary assessments of executive function in preterm and full-term preschoolers

Executive functions (EFs) are interrelated cognitive processes that have been studied in relation to behavior, attention, academic achievement, and developmental disorders. Studies of EF skills assessed through parent report and performance-based measures show correlations between them ranging from none to modest. Few studies have examined the relationship between EF skills measured through parent report and performance-based measures in relation to adaptive function. The present study included preschool children born preterm as a population at high risk for EF impairments. Preschool children (N = 149) completed a battery of EF tasks that assess working memory, response inhibition, idea generation, and attention shifting or cognitive flexibility. Parents reported on children's EF and adaptive skills. Preterm children showed more parent-rated and performance-based EF impairments than did full-term children. The combined use of either parent report or performance-based measures resulted in the identification of a large number of children at risk for EF impairment, especially in the preterm group. Both parent report and performance-based EF measures were associated with children's adaptive function. EF skills are measurable in young child'ren, and we suggest that EF skills may serve as targets for intervention to improve functional outcomes. We recommend the use of both parent report and performance-based measures to characterize children's EF profiles and to customize treatment.

Spatial working memory deficits in male rats following neonatal hypoxic ischemic brain injury can be attenuated by task modifications

Hypoxia-ischemia (HI; reduction in blood/oxygen supply) is common in infants with serious birth complications, such as prolonged labor and cord prolapse, as well as in infants born prematurely (<37 weeks gestational age; GA). Most often, HI can lead to brain injury in the form of cortical and subcortical damage, as well as later cognitive/behavioral deficits. A common domain of impairment is working memory, which can be associated with heightened incidence of developmental disorders. To further characterize these clinical issues, the current investigation describes data from a rodent model of HI induced on postnatal (P)7, an age comparable to a term (GA 36–38) human. Specifically, we sought to assess working memory using an eight-arm radial water maze paradigm. Study 1 used a modified version of the paradigm, which requires a step-wise change in spatial memory via progressively more difficult tasks, as well as multiple daily trials for extra learning opportunity. Results were surprising and revealed a small HI deficit only for the final and most difficult condition, when a delay before test trial was introduced. Study 2 again used the modified radial arm maze, but presented the most difficult condition from the start, and only one daily test trial. Here, results were expected and revealed a robust and consistent HI deficit across all weeks. Combined results indicate that male HI rats can learn a difficult spatial working memory task if it is presented in a graded multi-trial format, but performance is poor and does not appear to remediate if the task is presented with high initial memory demand. Male HI rats in both studies displayed impulsive characteristics throughout testing evidenced as reduced choice latencies despite more errors. This aspect of behavioral results is consistent with impulsiveness as a core symptom of ADHD—a diagnosis common in children with HI insult. Overall findings suggest that task specific behavioral modifications are crucial to accommodating memory deficits in children suffering from cognitive impairments following neonatal HI.

Relation of neural structure to persistently low academic achievement: a longitudinal study of children with differing birth weights

OBJECTIVE

This study examined the relation of cerebral tissue reductions associated with VLBW to patterns of growth in core academic domains.

METHOD

Children born <750 g, 750 to 1,499 g, or >2,500 g completed measures of calculation, mathematical problem solving, and word decoding at time points spanning middle childhood and adolescence. K. A. Espy, H. Fang, D. Charak, N. M. Minich, and H. G. Taylor (2009, Growth mixture modeling of academic achievement in children of varying birth weight risk, Neuropsychology, Vol. 23, pp. 460-474) used growth mixture modeling to identify two growth trajectories (clusters) for each academic domain: an average achievement trajectory and a persistently low trajectory. In this study, 97 of the same participants underwent magnetic resonance imaging (MRI) in late adolescence, and cerebral tissue volumes were used to predict the probability of low growth cluster membership for each domain.

RESULTS

Adjusting for whole brain volume (wbv), each 1-cm(3) reduction in caudate volume was associated with a 1.7- to 2.1-fold increase in the odds of low cluster membership for each domain. Each 1-mm(2) decrease in corpus callosum surface area increased these odds approximately 1.02-fold. Reduced cerebellar white matter volume was associated specifically with low calculation and decoding growth, and reduced cerebral white matter volume was associated with low calculation growth. Findings were similar when analyses were confined to the VLBW groups.

CONCLUSIONS

Reduced volume of structures involved in connectivity, executive attention, and motor control may contribute to heterogeneous academic trajectories among children with VLBW.

A model of neurodevelopmental risk and protection for preterm infants

The purpose of this article is to introduce a model of neurodevelopmental risk and protection that may explain some of the relationships among biobehavioral risks, environmental risks, and caregiving behaviors that potentially contribute to neurobehavioral and cognitive outcomes. Infants born before 30 weeks of gestation have the poorest developmental prognosis of all infants. These infants have lengthy hospitalization periods in the neonatal intensive care unit (NICU,) an environment that is not always supportive of brain development and long-term developmental needs. The model supports the premise that interventions focused on neuroprotection during the neonatal period have the potential to positively affect long-term developmental outcomes for vulnerable very preterm infants. Finding ways to better understand the complex relationships among NICU-based interventions and long-term outcomes are important to guiding caregiving practices in the NICU.

Visuospatial working memory in toddlers with a history of periventricular Leukomalacia: an EEG narrow-band power analysis

BACKGROUND

Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries have also been reported, particularly in the dorsomedial nucleus and the cortex. Both structures have been related to working memory (WM) processes. The aim of this study was to compare behavioral performances and EEG power spectra during a visuospatial working memory task (VSWMT) of toddlers with a history of PVL and healthy toddlers.

METHODOLOGY/PRINCIPAL FINDINGS

A prospective, comparative study of WM was conducted in toddlers with a history of PVL and healthy toddlers. The task responses and the EEG narrow-band power spectra during a VSWMT were compared in both groups. The EEG absolute power was analyzed during the following three conditions: baseline, attention and WM retention. The number of correct responses was higher in the healthy group (20.5 ± 5.0) compared to the PVL group (16.1 ± 3.9) (p = 0.04). The healthy group had absolute power EEG increases (p ≤ 0.05) during WM compared to the attention condition in the bilateral frontal and right temporal, parietal and occipital regions in frequencies ranging from 1.17 to 2.34 Hz and in the right temporal, parietal and occipital regions in frequencies ranging from 14.06 to 15.23 Hz. In contrast, the PVL group had absolute power increases (p ≤ 0.05) in the bilateral fronto-parietal, left central and occipital regions in frequencies that ranged from 1.17 to 3.52 Hz and in the bilateral frontal and right temporal regions in frequencies ranging from 9.37 to 19.14 Hz.

CONCLUSIONS/SIGNIFICANCE

This study provides evidence that PVL toddlers have visuospatial WM deficits and a very different pattern of absolute power increases compared to a healthy group of toddlers, with greater absolute power in the low frequency range and widespread neuronal networks in the WM retention phase.

Assessing independency in daily activities in very preterm children at preschool age

This study investigates whether very low birth weight (VLBW) preschoolers experience disability in daily activities and what the risk factors for disability in daily activities are. The Dutch Pediatric Evaluation of Disability Inventory (PEDI-NL) was used to detect disability in daily activities in 143 VLBW children without cerebral palsy (CP) at 44 months of corrected age (CA). Data from the psychomotor-developmental index (PDI) and the mental developmental index (MDI) of the Bayley Scales of Infant Development II (BSID II) at 24 months CA, and data relating to perinatal and socio-economic status were available. Disability in daily activities was found in 27 (19%) VLBW children without CP. High frequencies of disability were found in 19 (13%) children on the mobility domain and in 12 (8%) children on the social functioning domain. The multiple logistic regression analyses showed that low BSID II outcomes (<2 SD) were risk factors for disability in the mobility domain, but not for disability in the social functioning domain. The predictive value of the BSID II outcomes is moderate, 46% of the VLBW children with a low PDI and 44% with a low MDI developed a disability in the mobility domain. This study showed a higher frequency of disability in daily activities in VLBW preschoolers compared to term born peers. Therefore, it is suggested to assess VLBW children's performance of daily activities before they start school.

Emerging executive skills in very preterm children at 2 years corrected age: a composite assessment

Executive Function (EF) deficits have previously been identified in preterm children. However, only recently have emerging executive functions been studied in preschool children who were born preterm without major brain damage. Our study provides a broad assessment of EFs in 72 extremely preterm births (gestational age < 34 weeks and birth weight < 2500 g) and 73 full-term children, born between 2006 and 2008, at 24 months of corrected age. Three factors were extracted from the EF administered measures: working memory, cognitive flexibility, and impulsivity control. Only cognitive flexibility was found to discriminate preterm children from controls.

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.

Neonatal white matter abnormalities predict global executive function impairment in children born very preterm

Using prospective longitudinal data from 110 very preterm and 113 full term children, this article describes the executive functioning abilities of very preterm children at age 4, and examines relations between the extent of white matter abnormality on neonatal magnetic resonance imaging (MRI) and later executive function outcomes. Very preterm children performed less well than full term children on measures of planning ability, cognitive flexibility, selective attention, and inhibitory control. Executive impairments at age 4 were confined to preterm children with mild or moderate-severe white matter abnormalities on MRI. Findings support the importance of cerebral white matter integrity for later executive function.

Processing speed mediates executive function difficulties in very preterm children in middle childhood

Executive function and attention difficulties are reported in very preterm (VPT) children at school entry, but it is unclear if these remain at later ages and/or if these difficulties are mediated by more basic functions, such as processing speed. Processing speed has been shown to underlie academic and behavioral problems in VPT children in middle childhood (Mulder, Pitchford, & Marlow, 2010, 2011), so may also underpin executive function and attention difficulties. We investigated this by comparing VPT (gestational age <31 weeks; N = 56) to term children (N = 22) aged 9-10 years on a comprehensive battery of executive function and attention tasks from the Test of Everyday Attention for Children (Manly, Robertson, Anderson, & Nimmo-Smith, 1999) and NEPSY (Korkman, Kirk, & Kemp, 1998). Selective and sustained attention, inhibition, working memory, shifting, verbal fluency, planning, and processing speed were examined. Group differences favoring term children were shown on most executive function tasks (i.e., inhibition, working memory, verbal fluency, and shifting), all of which were mediated by slow processing speed in the VPT group, except response inhibition. Seemingly, processing speed is an important determinant underpinning many neuropsychological deficits seen in VPT children in middle childhood.

Anterior cingulate and frontal lobe white matter spectroscopy in early childhood of former very LBW premature infants

Neurometabolic sequelae of children born at very LBW (VLBW) are not well characterized in early childhood. Proton magnetic resonance spectroscopy (1H-MRS) and developmental assessments were acquired from children age 18-22 mo (16 VLBW/7 term) and 3-4 y (12 VLBW/8 term) from the anterior cingulate and left frontal periventricular white matter. Metabolites obtained included combined N-acetylaspartylglutamate and N-acetylaspartate (NAA), total choline-containing compounds (Cho), combined glutamate and glutamine (Glx), combined creatine and phosphocreatine (Cr), myoinositol (mI), and the following ratios: NAA/Cr, Cho/Cr, Glx/Cr, mI/Cr, and NAA/Cho. Significant differences were present only in white matter: at 18-22 mo, NAA was decreased in VLBW children (p < 0.04), and at 3-4 y, VLBW children showed lower Cr (p < 0.01), lower NAA/Cho (p < 0.005), higher Glx/Cr (p < 0.02), and higher Cho/Cr (p < 0.005). On developmental testing, VLBW children scored lower on language expression (p < 0.05) and on the A-not-B test of early executive function (p < 0.01) at 18-22 mo and had lower verbal intelligence quotient (IQ) (p < 0.005), performance IQ (p < 0.04), and several measures of early executive function including the bear-dragon test (p < 0.004), gift delay (p < 0.07), and summary categorization score (p < 0.03) at 3-4 y. VLBW children may have neurometabolic and developmental abnormalities that persist at least through early childhood.

Individual differences in developmental trajectories of A-not-B performance in infants born preterm

Because early executive functioning is a potentially important predictor of developmental delay and learning difficulties in infants born preterm, this study assessed the effect of several perinatal predictors on the development of A-not-B performance between 7 and 14 months corrected age in 76 infants born preterm, and its relationship to subsequent global cognitive functioning. Latent Growth Modeling showed that gestational age was a predictor of initial level, and that birth weight and gender were predictors of the rate of developmental change in A-not-B performance. Moreover, initial level and rate of developmental change in A-not-B performance were predictive of global cognitive functioning.

A model of neurodevelopmental risk and protection for preterm infants

The purpose of this article is to introduce a model of neurodevelopmental risk and protection that may explain some of the relationships among biobehavioral risks, environmental risks, and caregiving behaviors that potentially contribute to neurobehavioral and cognitive outcomes. Infants born before 30 weeks of gestation have the poorest developmental prognosis of all infants. These infants have lengthy hospitalization periods in the neonatal intensive care unit (NICU,) an environment that is not always supportive of brain development and long-term developmental needs. The model supports the premise that interventions focused on neuroprotection during the neonatal period have the potential to positively affect long-term developmental outcomes for vulnerable very preterm infants. Finding ways to better understand the complex relationships among NICU-based interventions and long-term outcomes are important to guiding caregiving practices in the NICU.

Development of executive function and attention in preterm children: a systematic review

We report on a systematic review of studies of executive function and attention in preterm children. Using meta-analysis, we confirm this is an area of weakness for preterm children, and show that the extent of difficulties is influenced by gestational age (GA), age at test, and skill under investigation. Effect size for selective and sustained attention and inhibition is related to GA. For studies with mean GA > or = 26 weeks, selective attention skills catch up with age, phonemic fluency skills are increasingly delayed, and ongoing deviance is shown for shifting skills (when assessed with specific measures). Implications for research and practice are discussed.

Low-level lead exposure and contingency-based responding in preschoolers: an exploratory study

Two reversal paradigm tasks (spatial reversal and spatial reversal with irrelevant color cues) originally designed to assess contingency-based responding in primates were adapted for use with 139 preschool children with a mean peak blood lead level (BLL) of 4.2 microg/dl (SD = 2.2). Sixty-nine children with BLL > or =5 microg/dl and 70 children with BLL of <5 microg/dl were included. Results indicated that preschool children with low-level lead exposure take longer to learn associations than preschool children with very low levels of lead exposure, and this difference cannot be attributed to increased distractibility or perseverative responding. These results support the use of these measures to assess specific cognitive functions in preschool children.

The cerebral cortex overlying periventricular leukomalacia: analysis of pyramidal neurons

The role of the cerebral cortex in the cognitive deficits in preterm survivors is poorly understood. Periventricular leukomalacia (PVL), the key feature of encephalopathy of prematurity, is characterized by periventricular necrotic foci and diffuse gliosis in the surrounding cerebral white matter. Here, we tested the hypothesis that reductions in the density of layer I neurons and/or pyramidal neurons in layers III and/or V are associated with PVL, indicating cortical pathology potentially associated with cognitive deficits in long-term survivors. In controls (23 gestational weeks to 18 postnatal months) (n = 15), a lack of significant differences in pyramidal density among incipient Brodmann areas suggested that cytoarchitectonic differences across functional areas are not fully mature in the fetal and infant periods. There was a marked reduction (38%) in the density of layer V neurons in all areas sampled in the PVL cases (n = 17) compared to controls (n = 12) adjusted for postconceptional age at or greater than 30 weeks, when the six-layer cortex is visually distinct (P < 0.024). This may reflect a dying-back loss of somata complicating transection of layer V axons projecting through the necrosis in the underlying white matter. This study underscores the potential role of secondary cortical injury in the encephalopathy of prematurity.

Childhood fears, neurobehavioral functioning and behavior problems in school-age children

The objective is to examine underlying associations between childhood fears, behavior problems and neurobehavioral functioning (NBF) in school-age children. Healthy, regular school children (N = 135), from second, fourth and sixth grade classes were assessed. Data regarding children's fears and behavioral problems were obtained with the Revised Fear Survey Schedule for Children, the Child Behavior Checklist, and NBF was assessed using a computerized neurobehavioral evaluation system. Significant correlations between childhood fears and NBF measures and somatic complaints were found. Children who reported higher levels of fears demonstrated lower working memory span (r = 0.24, p < 0.05), lower motor speed (r = -0.23, p < 0.05), and had more somatic complaints (r = 0.20, p < 0.05). Furthermore, younger children reported less fears than older ones and girls reported more fears than boys. These results highlight significant association between childhood fears, NBF and behavior problems in a non-clinical group children. Lower working memory span is an important component of executive control that may be an underlying factor in fears and anxiety in children.

Attentional networks efficiency in preterm children

Recent studies have reported specific executive and attentional deficits in preterm children. However, the majority of this research has used multidetermined tasks to assess these abilities, and the interpretation of the results lacks an explicit theoretical backdrop to better understand the origin of the difficulties observed. In the present study, we used the Child Attention Network Task (Child ANT; Rueda et al. 2004) to assess the efficiency of the alerting, orienting and executive control networks. We compared the performance of 25 preterm children (gestational age < or = 32 weeks) to 25 full-term children, all between 5(1/2) and 6(1/2) years of age. Results showed that, as compared to full-term children, preterm children were slower on all conditions of the Child ANT and had a specific deficit in executive control abilities. We also observed a significantly higher correlation between the orienting and executive control networks in the preterm group, suggesting less differentiation of these two networks in this population.

Long-term outcomes of bronchopulmonary dysplasia

As more very preterm infants survive, more survivors will have bronchopulmonary dysplasia (BPD). Children with BPD have higher rates of cognitive, educational and behavioural impairments, and also reduced lung function, through childhood and into early life than would normally be expected. The importance of these neurological and respiratory problems later into adult life needs to be determined.

Growth mixture modeling of academic achievement in children of varying birth weight risk

The extremes of birth weight and preterm birth are known to result in a host of adverse outcomes, yet studies to date largely have used cross-sectional designs and variable-centered methods to understand long-term sequelae. Growth mixture modeling (GMM) that utilizes an integrated person- and variable-centered approach was applied to identify latent classes of achievement from a cohort of school-age children born at varying birth weights. GMM analyses revealed 2 latent achievement classes for calculation, problem-solving, and decoding abilities. The classes differed substantively and persistently in proficiency and in growth trajectories. Birth weight was a robust predictor of class membership for the 2 mathematics achievement outcomes and a marginal predictor of class membership for decoding. Neither visuospatial-motor skills nor environmental risk at study entry added to class prediction for any of the achievement skills. Among children born preterm, neonatal medical variables predicted class membership uniquely beyond birth weight. More generally, GMM is useful in revealing coherence in the developmental patterns of academic achievement in children of varying weight at birth and is well suited to investigations of sources of heterogeneity.

Early school-based learning difficulties in children born very preterm

BACKGROUND

Educational underachievement is a major morbidity associated with very preterm (VPT) birth. However, few studies have examined early school outcomes with most employing global, clinic based measures.

OBJECTIVE

To examine the early school achievement in a cohort of children born VPT and studied to age 6 years.

METHODS

A regional cohort of 102 VPT children (</=33 weeks GA) were followed prospectively alongside a comparison group of 108 full term (FT) children born during the same period (1998-2000). At 6 years corrected age, all children underwent a comprehensive neurodevelopmental evaluation that included the Woodcock-Johnson Tests of Achievement (WJ-III), teacher report and national numeracy and literacy test results. Rates of specific learning disabilities (LD) were also examined.

RESULTS

VPT children performed less well than FT children on WJ-III subtests (ps<.05), national tests (ps<.01), and in all curricular areas rated by teachers (ps<.01) except expressive language. Even VPT children without severe neurodevelopmental impairment scored lower on the WJ-III math, national tests (ps<.05) and were 2-3 times more likely to show delays (ps<.02) in math (43% vs. 19%), written language (36% vs. 22%), language comprehension (26% vs. 14%), handwriting (36% vs. 17%), spelling (38% vs. 30%) and physical education (33% vs. 11%). They were also twice as likely as FT children to have math LD (47% vs. 21%).

CONCLUSIONS

By age 6, a substantial proportion of VPT children are lagging behind their FT peers across multiple curriculum areas, with difficulties being most prominent in math. Findings highlight the need for early identification and educational supports to help maximise VPT children's learning opportunities during the transition to school.

Preterm infant hippocampal volumes correlate with later working memory deficits

Children born preterm exhibit working memory deficits. These deficits may be associated with structural brain changes observed in the neonatal period. In this study, the relationship between neonatal regional brain volumes and working memory deficits at age 2 years were investigated, with a particular interest in the dorsolateral prefrontal cortex, parietal cortex and the hippocampus. While the eligible sample consisted of 227 very preterm children who were born at the Royal Women's Hospital, Melbourne prior to 30 weeks gestation or weighing <1250 g, 156 children had complete data sets. Neonatal magnetic resonance images of the brain were obtained at term equivalent age and subsequently parcellated into eight sub-regions, while the hippocampus was manually segmented. The relationship between brain volumes for these regions and performance on a working memory task (delayed alternation) at 2 years of age was examined. Very preterm children who perseverated on the working memory task had significantly smaller hippocampal volumes than very preterm children who exhibited intact working memory, even after adjusting for relevant perinatal, sociodemographic and developmental factors. Preterm children appear to have altered hippocampal volumes by discharge from hospital which may have a lasting impact on working memory function.

Executive functioning in preschool children born very preterm: relationship with early white matter pathology

Despite evidence for executive dysfunction in school-aged preterm children, less is known about the early development of these difficulties or their underlying neuropathology. This study used prospective longitudinal data from a regional cohort of 88 very preterm and 98 full-term comparison children to examine the executive functioning (EF) of preschool children born very preterm. The relationship between the severity of neonatal cerebral white matter (WM) abnormalities on magnetic resonance imaging (MRI) at term equivalent and children's EF at ages two and four years (corrected age) was examined. At age four, very preterm children with WM abnormalities performed less well than full-term children on the Detour Reaching Box, a measure of behavioral inhibition and cognitive flexibility, even after controlling for child IQ, SES, and medical background. Examination of patterns of EF performance between the ages of 2 and 4 years showed that the performance of all groups improved with age. However, very preterm children with mild and moderate-severe WM abnormalities were characterized by higher rates of consistent performance impairments. These findings support the presence of early and persistent executive difficulties in preschool children born very preterm, and highlight the importance of white matter pathology in the development of executive impairments.

Perinatal pH and neuropsychological outcomes at age 3 years in children born preterm: an exploratory study

The impact of extreme prematurity and related hypoxic-ischemic events on brain development recently has begun to be characterized with modern neuroimaging methods, although comparatively less is known about the neuropathology in those born at heavier birth weights. Even subclinical levels of perinatal hypoxia-ischemia, as indexed by perinatal blood pH, are related to intelligence in school-aged children born preterm. Given the impact of hypoxia-ischemia on white matter and the emerging evidence of specific executive and mathematic deficits in children born preterm, the impact of perinatal hypoxia-ischemia on these outcomes was explored in children at relatively low-risk for sequelae. In a sample of 22 preschool children born preterm, arterial blood pH values obtained within the first 3 h of life were abstracted from review of hospital medical charts, and then related to specific cognitive task performance at age 3 years. Mean initial pH was in the normal to subclinical range. Initial pH appears to be a strong predictor of specific mathematics and controlled attention abilities, and is not limited to general verbal ability alone. However, initial pH was not related to performance on measures of motor impulsivity or working memory. As a screening index of subtle hypoxia-ischemia, these findings suggest that perinatal arterial blood pH warrants further study as a potential marker of subtle hypoxic-ischemic injury that likely affects cognitive outcome throughout childhood in those at risk due to preterm birth.

Behavior ratings of executive function among preschoolers with ADHD

The Behavior Rating Inventory of Executive Function-Preschool Version (BRIEF-P; Gioia, Espy, & Isquith, 2003) was developed to assess executive function (EF) behaviors in children aged 2 to 5 years. We compared parent ratings of 25 preschool children with ADHD to 25 age-, sex-, and SES-matched controls from the BRIEF-P standardization sample. Children with ADHD were rated significantly higher than controls (p < .01) on all five primary scales (Inhibit, Shift, Emotional Control, Working Memory, Plan/Organize), and on all four indices (Inhibitory Self Control, Flexibility, Emerging Metacognition, General Executive Composite). The largest effect size was on the Working Memory scale. All five BRIEF-P clinical scales were significantly intercorrelated in the control group, and seven of ten scale intercorrelations were significant in the ADHD group. Within the ADHD group, the BRIEF-P Index scores were significantly correlated with ratings on the Conners' Parent Rating Scale, but only moderately correlated with an estimate of Verbal IQ. The BRIEF-P had low, non-significant correlations with performance-based measures of EF, and patterns of correlations were not significantly different than those between the BRIEF-P and non-EF measures (sensorimotor, receptive vocabulary). Similar to its predecessor, the BRIEF-P is sensitive to symptoms of ADHD, but appears to measure different elements of EF than those tapped by performance-based measures.

Impaired executive functioning in young adults born very preterm

Individuals born very preterm (VPT) are at increased risk of perinatal brain injury and long-term cognitive and behavioral problems. Executive functioning, in particular, has been shown to be impaired in VPT children and adolescents. This study prospectively assessed executive function in young adults who were born VPT (<33 weeks of gestation) [n = 61; mean age, 22.25 (+/-1.07) years; range, 20.62-24.78 years] and controls [n = 64; mean age, 23.20 (+/-1.48) years; range, 19.97-25.46 years]. Tests used comprised the Wechsler Abbreviated Scale of Intelligence (WASI), the Hayling Sentence Completion Test (HSCT), the Controlled Oral Word Association Test (COWAT), the Animal and Object test, the Trail-Making Test (TMT), and the Test of Attentional Performance (TAP). VPT participants showed specific executive function impairments in tasks involving response inhibition and mental flexibility, even when adjusting for IQ, gender, and age. No significant associations were observed between executive function test scores and perinatal variables or neonatal ultrasound classification. The results suggest that, although free from major physical disability, VPT young adults perform worse than controls on tasks involving selective aspects of executive processing, such as mental flexibility and response inhibition.