Verbal memory deficits in children with less than 750 g birth weight

Cognitive and academic outcomes of children born extremely preterm

Extremely preterm birth is associated with increased risk for a spectrum of neurodevelopmental problems. This review describes the nature of cognitive and academic outcomes of extremely preterm survivors across childhood and adolescence. Evidence across meta-analyses and large prospective birth cohorts indicate that early developmental difficulties in children born extremely preterm do not resolve with age and are not improving over time despite advancements in neonatal care. While extremely preterm birth confers increased risk of widespread cognitive difficulties, considerable heterogeneity in outcomes is evident across individuals. There is a continued need for high-quality longitudinal studies to understand the developmental progression of cognitive and academic skills following extremely preterm birth, and greater focus on understanding contributing factors that may help to explain the individual variability in cognitive and academic outcomes of extremely preterm survivors.

Uneven Linguistic Outcome in Extremely Preterm Children

One primary problem in extremely preterm children is the occurrence of atypical language development. The aim of this study was to explore the components of language (articulatory phonetics, lexicon and syntax) in comprehension and production in extremely preterm children between the 4th and 5th year of age. The language section of the Preschool Neuropsychological Test was administered to 20 extremely preterm monolingual Italian children (GA < 28 weeks) and to a control sample of 40 full term children (GA > 37 weeks), matched for age and non-verbal IQ. Language comprehension was fully efficient in all of the components that we assessed. In the tasks of language production the clinical sample fared much worse than their age and IQ matched controls and the differences were highly significant (p < .001). Language acquisition in extremely preterm children may follow uneven developmental trajectories: language comprehension can be spared in the face of a selective impairment of language production at the level of articulatory phonetics and syntax.

Lack of association between hypothyroxinemia of prematurity and transient thyroid abnormalities with adverse long term neurodevelopmental outcome in very low birth weight infants

Introduction

The association between hypothyroxinemia of prematurity with neurodevelopment was controversial.

Objectives

To compare 5 year neurodevelopmental outcomes of very low birth weight (VLBW) infants with hypothyroxinemia of prematurity against those without.

Methods

Retrospective cohort study in a single tertiary neonatal centre of VLBW infants born between the year 2008 to 2011. Comparisons were made between all abnormal and normal thyroid function controls using cord thyroid function tests, thyroid function tests during admission and pre-discharge thyroid function test done at term equivalent age. At 2 years corrected age, Bayley scales of infant and toddler development–third edition and Vineland II adaptive behaviour scales (VABS) were collected. At 5 years, Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III), Bracken School Readiness Assessment, VABS and Beery Test of Visual-Motor Integration were collected.

Results

110 subjects were studied at 2 years corrected age and 80 subjects at 5 years old. 29 infants had abnormal thyroid function test (10 infants with hypothyroxinemia of prematurity and 19 infants with transient thyroid abnormalities). There were no significant difference in the 2 years and 5 years developmental outcome between infants with and without hypothyroxinemia of prematurity (p-value>0.05); and between infants with and without transient thyroid abnormalities (p-value>0.05). There were no significant difference in neurological, visual and hearing impairment between infants with or without hypothyroxinemia of prematurity (p-value>0.05).

Conclusions

Hypothyroxinemia of prematurity or transient thyroid abnormalities in VLBW infants were not associated with poorer neurodevelopment and did not support the need for levothyroxine supplementation.

Implicit Learning Abilities in Adolescents Born Very Preterm

Very preterm birth is associated with neurodevelopmental impairments and outcomes have not improved over the last decades. Insight in learning processes is important for the development of effective interventions. Implicit learning is of particular interest because of its independence from working memory processes that are affected by preterm birth. This study examined implicit learning abilities in 49 very preterm and 61 full-term 13-year-old adolescents. The degree of implicit learning was not different between groups. This indicates intact implicit learning abilities in adolescents born very preterm. Implicit learning strategies may be beneficial for skill learning in very preterm born children.

Aberrant structural and functional connectivity and neurodevelopmental impairment in preterm children

Background

Despite advances in antenatal and neonatal care, preterm birth remains a leading cause of neurological disabilities in children. Infants born prematurely, particularly those delivered at the earliest gestational ages, commonly demonstrate increased rates of impairment across multiple neurodevelopmental domains. Indeed, the current literature establishes that preterm birth is a leading risk factor for cerebral palsy, is associated with executive function deficits, increases risk for impaired receptive and expressive language skills, and is linked with higher rates of co-occurring attention deficit hyperactivity disorder, anxiety, and autism spectrum disorders. These same infants also demonstrate elevated rates of aberrant cerebral structural and functional connectivity, with persistent changes evident across advanced magnetic resonance imaging modalities as early as the neonatal period. Emerging findings from cross-sectional and longitudinal investigations increasingly suggest that aberrant connectivity within key functional networks and white matter tracts may underlie the neurodevelopmental impairments common in this population.

Main body

This review begins by highlighting the elevated rates of neurodevelopmental disorders across domains in this clinical population, describes the patterns of aberrant structural and functional connectivity common in prematurely-born infants and children, and then reviews the increasingly established body of literature delineating the relationship between these brain abnormalities and adverse neurodevelopmental outcomes. We also detail important, typically understudied, clinical, and social variables that may influence these relationships among preterm children, including heritability and psychosocial risks.

Conclusion

Future work in this domain should continue to leverage longitudinal evaluations of preterm infants which include both neuroimaging and detailed serial neurodevelopmental assessments to further characterize relationships between imaging measures and impairment, information necessary for advancing our understanding of modifiable risk factors underlying these disorders and best practices for improving neurodevelopmental trajectories in this high-risk clinical population.

Effects of extreme prematurity and kindergarten neuropsychological skills on early academic progress

OBJECTIVE

The study was designed to investigate the effect of extreme prematurity on growth in academic achievement across the early school years and the validity of kindergarten neuropsychological skills as predictors of achievement.

METHOD

A 2001-2003 birth cohort of 145 extremely preterm/extremely low birth weight (EPT/ELBW) children from a single medical center, along with 111 normal birth weight (NBW) classmate controls, were recruited during their first year in kindergarten and followed annually across the next 2 years in school. Mixed model analysis was conducted to compare the groups on growth in achievement across years and examine kindergarten neuropsychological skills as predictors of growth.

RESULTS

The EPT/ELBW group scored significantly below NBW controls on all achievement tests across years and had higher rates of special education placement and grade repetition. Despite limited catch-up of the EPT/ELBW group to the NBW controls in spelling, group differences were generally stable. Differences in spelling and mathematics achievement remained significant when controlling for global intelligence or excluding children who had intellectual or neurosensory impairments or repeated a grade. Higher scores on kindergarten tests of multiple neuropsychological ability domains predicted higher achievement levels and steeper growth in achievement.

CONCLUSIONS

The findings document persistent academic weaknesses in EPT/ELBW children across the early school years. Results point to the need for preschool interventions to enhance academic readiness and suggest that neuropsychological skills assessed in kindergarten are useful in identifying individual differences in early learning progress. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Early language processing efficiency predicts later receptive vocabulary outcomes in children born preterm

As rates of prematurity continue to rise, identifying which preterm children are at increased risk for learning disabilities is a public health imperative. Identifying continuities between early and later skills in this vulnerable population can also illuminate fundamental neuropsychological processes that support learning in all children. At 18 months adjusted age, we used socioeconomic status (SES), medical variables, parent-reported vocabulary, scores on the Bayley Scales of Infant and Toddler Development (third edition) language composite, and children's lexical processing speed in the looking-while-listening (LWL) task as predictor variables in a sample of 30 preterm children. Receptive vocabulary as measured by the Peabody Picture Vocabulary Test (fourth edition) at 36 months was the outcome. Receptive vocabulary was correlated with SES, but uncorrelated with degree of prematurity or a composite of medical risk. Importantly, lexical processing speed was the strongest predictor of receptive vocabulary (r = -.81), accounting for 30% unique variance. Individual differences in lexical processing efficiency may be able to serve as a marker for information processing skills that are critical for language learning.

Memory function and hippocampal volumes in preterm born very-low-birth-weight (VLBW) young adults

The hippocampi are regarded as core structures for learning and memory functions, which is important for daily functioning and educational achievements. Previous studies have linked reduction in hippocampal volume to working memory problems in very low birth weight (VLBW; ≤ 1500 g) children and reduced general cognitive ability in VLBW adolescents. However, the relationship between memory function and hippocampal volume has not been described in VLBW subjects reaching adulthood. The aim of the study was to investigate memory function and hippocampal volume in VLBW young adults, both in relation to perinatal risk factors and compared to term born controls, and to look for structure-function relationships. Using Wechsler Memory Scale-III and MRI, we included 42 non-disabled VLBW and 61 control individuals at age 19-20 years, and related our findings to perinatal risk factors in the VLBW-group. The VLBW young adults achieved lower scores on several subtests of the Wechsler Memory Scale-III, resulting in lower results in the immediate memory indices (visual and auditory), the working memory index, and in the visual delayed and general memory delayed indices, but not in the auditory delayed and auditory recognition delayed indices. The VLBW group had smaller absolute and relative hippocampal volumes than the controls. In the VLBW group inferior memory function, especially for the working memory index, was related to smaller hippocampal volume, and both correlated with lower birth weight and more days in the neonatal intensive care unit (NICU). Our results may indicate a structural-functional relationship in the VLBW group due to aberrant hippocampal development and functioning after preterm birth.

Free thyroxine levels after very preterm birth and neurodevelopmental outcomes at age 7 years

BACKGROUND AND OBJECTIVES

Preterm infants commonly have transient hypothyroxinemia of prematurity after birth, which has been associated with deficits in general intellectual functioning, memory, attention, and academic achievement. However, research has predominantly focused on thyroxine levels in the first 2 weeks of life and outcomes are limited to the preschool period. Our objective was to evaluate the relationships between free thyroxine (fT₄) levels over the first 6 weeks after very preterm (VPT) birth with cognitive functioning and brain development at age 7 years.

METHODS

A total of 83 infants born VPT (<30 weeks' gestation) had fT₄ concentrations measured postnatally and 2- and 6-week area under the curve (AUC) summary measures were calculated. Follow-up at age 7 years included a neuropsychological assessment and brain MRI. Univariable and multivariable regression modeling was used where AUC for fT₄ was the main predictor of neurodevelopmental outcome at age 7 years.

RESULTS

Multivariable modeling revealed that higher, not lower, postnatal fT₄ levels (2-week AUC) were associated with poorer cognitive performances at age 7 years on tasks of verbal learning (P = .02), verbal memory (P = .03), and simple reaction time (P < .001). A similar pattern of results was found when the 6-week AUC was examined. No significant associations between postnatal fT₄ levels and brain volumes at age 7 years were identified.

CONCLUSIONS

Results are contradictory to previous observations and suggest that after adjustment for confounders, higher postnatal fT₄ levels in VPT infants, rather than lower levels, may be a marker of adverse neuropsychological development in childhood.

Neuropsychological outcomes of children born very preterm

Considerable research has investigated the consequences of being born very preterm (VP; <32 weeks of gestation), especially in relation to cognitive functioning. While numerous cognitive and neuropsychological outcome studies have been published, it is important to consider methodological issues when reviewing this research, as the generalizability of the studies varies greatly. This article describes the nature of cognitive difficulties confronting VP children, both in terms of the frequency and severity of deficits. The breadth of cognitive difficulties reported in this population implies a generalized cognitive impairment; however, the presence of selective or primary cognitive deficits is discussed. It is concluded that whereas mortality and neonatal morbidity rates have decreased significantly in VP infants in recent decades, these children continue to be at significant risk for cognitive impairments and need to be closely monitored throughout childhood.

Hippocampal volume and memory and learning outcomes at 7 years in children born very preterm

Using magnetic resonance imaging, this study compared hippocampal volume between 145 very preterm children and 34 children born full-term at 7 years of age. The relationship between hippocampal volume and memory and learning impairments at 7 years was also investigated. Manual hippocampal segmentation and subsequent three-dimensional volumetric analysis revealed reduced hippocampal volumes in very preterm children compared with term peers. However, this relationship did not remain after correcting for whole brain volume and neonatal brain abnormality. Contrary to expectations, hippocampal volume in the very preterm cohort was not related to memory and learning outcomes. Further research investigating the effects of very preterm birth on more extensive networks in the brain that support memory and learning in middle childhood is needed.

Human infancy…and the rest of the lifespan

Human infancy has been studied as a platform for hypothesis and theory testing, as a major physiological and psychological adjustment, as an object of adults' effects as well as a source of effects on adults, for its comparative value, as a stage of life, and as a setting point for the life course. Following an orientation to infancy studies, including previous reviews and a discussion of the special challenges infants pose to research, this article focuses on infancy as a foundation and catalyst of human development in the balance of the life course. Studies of stability and prediction from infancy illustrate the depth and complexity of modern research on infants and provide a long-awaited reply to key philosophical and practical questions about the meaningfulness and significance of infancy.

A history of low birth weight alters recovery following a future head injury: a case series

OBJECTIVE

Low birth weight (LBW; below 2500 grams) is a general risk factor for a variety of neurodevelopmental difficulties. However, these children may remain more vulnerable to neurologic and environmental insults occurring years later. This prospective case series reports on children who sustained a mild, moderate, or severe traumatic brain injury (TBI) in middle childhood but who had also been born with birth weights below 2500 grams.

PARTICIPANTS

PARTICIPANTS were 14 children with mild, moderate, or severe traumatic brain injury (TBI), 5 of whom had birth weights under 2500 grams (LBW) and 9 children with normal birth weight (NBW). All participants were drawn from a larger study on the long-term cognitive and behavioral impact of pediatric TBI and were matched on age, estimated socioeconomic status (SES), and severity of TBI (with NBW children actually having a slightly worse overall injury severity).

RESULTS

At baseline, both groups exhibited similar scores on WJ-R Letter Word Identification and Calculations, Tower of London number solved, and CVLT-C total correct. Baseline group differences were observed on the CELF-III Formulated Sentences (NBW > LBW) and on the VABS Adaptive Behavior Composite and Socialization subdomain (LBW > NBW). Over 2 years, relative to the NBW group, the LBW group evidenced declines on both WJ-R subtests, CVLT-C total correct, CELF-III Formulated Sentences, and VABS Adaptive Behavior Composite and Socialization.

CONCLUSIONS

Although preliminary in nature due to small sample size, findings suggest a history of LBW influences the recovery trajectory following childhood TBI. Academic and adaptive functioning and verbal memory appeared particularly affected.

Outcomes of infants born at 22 and 23 weeks' gestation

OBJECTIVE

To provide instructive information on death and neurodevelopmental outcomes of infants born at 22 and 23 weeks' gestational age.

METHODS

The study cohort consisted of 1057 infants born at 22 to 25 weeks in the Neonatal Research Network, Japan. Neurodevelopmental impairment (NDI) at 36 to 42 months' chronological age was defined as any of the following: cerebral palsy, hearing impairment, visual impairment, and a developmental quotient <70. A systematic review was performed by using databases of publications of cohort studies with neonatal and neurodevelopmental outcomes at 22 and 23 weeks.

RESULTS

Numbers and incidences (%) of infants with death or NDI were 60 (80%) at 22 weeks and 156 (64%) at 23 weeks. In logistic regression analysis, gestational ages of 22 weeks (odds ratio [OR]: 5.40; 95% confidence interval [CI]: 2.48-11.76) and 23 weeks (OR: 2.14; 95% CI: 1.38-3.32) were associated with increased risk of death or NDI compared with 24 weeks, but a gestational age of 25 weeks (OR: 0.65; 95% CI: 0.45-0.95) was associated with decreased risk of death or NDI. In the systematic review, the medians (range) of the incidence of death or NDI in 8 cohorts were 99% (90%-100%) at 22 weeks and 98% (67%-100%) at 23 weeks.

CONCLUSIONS

Infants born at 22 and 23 weeks' gestation were at higher risk of death or NDI than infants at born at 24 weeks. However, outcomes were improved compared with those in previous studies. There is a need for additional discussions on interventions for infants born at 22 or 23 weeks' gestation.

Neonatal brain abnormalities and memory and learning outcomes at 7 years in children born very preterm

Using prospective longitudinal data from 198 very preterm and 70 full term children, this study characterised the memory and learning abilities of very preterm children at 7 years of age in both verbal and visual domains. The relationship between the extent of brain abnormalities on neonatal magnetic resonance imaging (MRI) and memory and learning outcomes at 7 years of age in very preterm children was also investigated. Neonatal MRI scans were qualitatively assessed for global, white-matter, cortical grey-matter, deep grey-matter, and cerebellar abnormalities. Very preterm children performed less well on measures of immediate memory, working memory, long-term memory, and learning compared with term-born controls. Neonatal brain abnormalities, and in particular deep grey-matter abnormality, were associated with poorer memory and learning performance at 7 years in very preterm children. Findings support the importance of cerebral neonatal pathology for predicting later memory and learning function.

Hippocampal shape variations at term equivalent age in very preterm infants compared with term controls: perinatal predictors and functional significance at age 7

The hippocampus undergoes rapid growth and development in the perinatal months. Infants born very preterm (VPT) are vulnerable to hippocampal alterations, and can provide a model of disturbed early hippocampal development. Hippocampal shape alterations have previously been associated with memory impairment, but have never been investigated in infants. The aims of this study were to determine hippocampal shape differences between 184 VPT infants (<30 weeks' gestation or <1250 g at birth) and 32 full-term infants, effects of perinatal factors, and associations between infant hippocampal shape and volume, and 7 year verbal and visual memory (California Verbal Learning Test - Children's Version and Dot Locations). Infants underwent 1.5 T magnetic resonance imaging at term equivalent age. Hippocampi were segmented, and spherical harmonics-point distribution model shape analysis was undertaken. VPT infants' hippocampi were less infolded than full-term infants, being less curved toward the midline and less arched superior-inferiorly. Straighter hippocampi were associated with white matter injury and postnatal corticosteroid exposure. There were no significant associations between infant hippocampal shape and 7 year memory measures. However, larger infant hippocampal volumes were associated with better verbal memory scores. Altered hippocampal shape in VPT infants at term equivalent age may reflect delayed or disrupted development. This study provides further insight into early hippocampal development and the nature of hippocampal abnormalities in prematurity.

School-age outcomes of extremely preterm or extremely low birth weight children

OBJECTIVE

Research is required to monitor changes in the nature of neurobehavioral deficits in extremely preterm (EP) or extremely low birth weight (ELBW) survivors. This study examines cognitive, academic, and behavioral outcomes at age 8 years for a regional cohort of EP/ELBW children born in 1997.

METHODS

The EP/ELBW cohort comprised all live births with a gestational age <28 weeks (EP) or birth weight <1000 g (ELBW) born in the state of Victoria, Australia, in 1997. Of 317 live births, 201 (63.4%) survived to 2 years of age.A term/normal birth weight (T/NBW) cohort was recruited comprising 199 infants with birthweights ≥2500 g or gestational age ≥37 weeks [corrected]. Measures of intellectual ability, educational achievement, and behavior were administered at age 8.

RESULTS

Retention was 94% for the EP/ELBW group and 87% for the T/NBW group. The EP/ELBW group performed poorer than the T/NBW group on measures of IQ, educational achievement, and certain behavioral domains, even after adjustment for sociodemographic factors and exclusion of children with neurosensory impairment. The rate of any neurobehavioral impairment was elevated in the EP/ELBW group (71% vs 42%), and one-half of subjects had multiple impairments. The outcomes for those with <750 g birth weight or <26 weeks' gestational age were similar to those with a birth weight of 750 to 999 g or a gestational age of 26 to 27 weeks, respectively.

CONCLUSIONS

Despite ongoing improvements in the management of EP/ELBW infants, the rate of neurobehavioral impairment at school-age remains too high relative to controls.

Memory processes in learning disability subtypes of children born preterm

The purpose of this study was to evaluate immediate auditory and visual memory processes in learning disability subtypes of 40 children born preterm. Three subgroups of children were examined: (a) primary language disability group (n = 13), (b) perceptual-motor disability group (n = 14), and (c) no learning disability diagnosis group without identified language or perceptual-motor learning disability (n = 13). Between-group comparisons indicate no significant differences in immediate auditory or visual memory performances between language and perceptual-motor learning disability groups. Within-group comparisons revealed that both learning disability groups performed significantly lower on a task of immediate memory when the mode of stimulus presentation and mode of response were visual.

Memory in ASD: have we been barking up the wrong tree?

In this theoretical note, possible neural causes of episodic memory impairment in individuals with ASD and currently normal intellectual and linguistic function are considered. The neural causes most commonly argued for are hippocampal or prefrontal cortex dysfunction, associated with impaired neural connectivity. It is argued here that a hippocampal dysfunction hypothesis is weakened by differences in cued recall and paired associate learning in individuals with ASD compared with individuals with developmental or acquired hippocampus-related amnesia, and that recent findings on patients with posterior parietal lesions (PPC) offer a better fit with the dissociation between free and cued recall observed in ASD. The PPC forms part of the default system subserving mindreading, among other functions, and an association between PPC dysfunction and memory impairment in ASD is consistent with recent suggestions that neural disconnectivity within the default system underlies behaviours diagnostic of ASD.

Consequence of preterm birth in early adolescence: the role of language on auditory short-term memory

This study tested the hypothesis that preterm early adolescents' short-term memory is compromised when presented with increasingly complex verbal information and that associated neuroanatomical volumes would differ between preterm and term groups. Forty-nine preterm and 20 term subjects were evaluated at age 12 years with neuropsychological measures and magnetic resonance imaging (MRI). There were no differences between groups in simple short-term and working memory. Preterm subjects performed lower on learning and short-term memory tests that included increased verbal complexity. They had reduced right parietal, left temporal, and right temporal white matter volumes and greater bilateral frontal gray and right frontal white matter volumes. There was a positive association between complex working memory and the left hippocampus and frontal white matter in term subjects. While not correlated, memory scores and volumes of cortical regions known to subserve language and memory were reduced in preterm subjects. This study provides evidence of possible mechanisms for learning problems in former preterm infants.

Attention problems in a representative sample of extremely preterm/extremely low birth weight children

The aim of this study was to examine attention in a large, representative, contemporary cohort of children born extremely preterm (EP) and/or extremely low birth weight (ELBW). Participants included 189 of 201 surviving children born EP (<28 weeks' gestation) or ELBW (<1,000 g) in 1997 in the state of Victoria, Australia. A comparison group of 173 of 199 children born full term and normal birth weight (FT/NBW) were randomly selected matching for birth hospital, expected due date, gender, mother's country of birth, and health insurance status. Participants were assessed at 8 years of age on subtests from the Test of Everyday Attention for Children (TEA-Ch) and the Wechsler Intelligence Scale for Children-4th Edition (WISC-IV). Measures of selective attention, sustained attention, attention encoding, and executive attention (inhibition, shifting attention, and divided attention) were administered. To assess behavioral elements of inattention, the primary caregiver completed the Behavior Rating Inventory of Executive Function (BRIEF) and the Conners' ADHD/DSM-IV Scale (CADS-P). The EP/ELBW group performed more poorly across all cognitive and behavioral measures than the FT/NBW group, with the exception of inhibition. The EP/ELBW group also had significantly elevated rates of impairment in selective, sustained, shifting and divided attention, as well as attention deficit hyperactivity disorder (ADHD) symptoms. No significant gender or gradient effects (e.g., <26 weeks' gestation vs. ≥ 26 weeks' gestation) were identified. Neonatal medical factors were not strong predictors of attention, although necrotizing enterocolitis (NEC) and cystic periventricular leukomalacia (PVL) were independent predictors of selective attention. In conclusion, our comprehensive assessment of attention provides strong evidence that children born EP/ELBW are at increased risk for attentional impairments, and as such, this population should be monitored closely during early and middle childhood with a focus on attention functioning.

Specific language and reading skills in school-aged children and adolescents are associated with prematurity after controlling for IQ

Although studies of long-term outcomes of children born preterm consistently show low intelligence quotient (IQ) and visual-motor impairment, studies of their performance in language and reading have found inconsistent results. In this study, we examined which specific language and reading skills were associated with prematurity independent of the effects of gender, socioeconomic status (SES), and IQ. Participants from two study sites (N=100) included 9-16-year old children born before 36 weeks gestation and weighing less than 2500 grams (preterm group, n=65) compared to children born at 37 weeks gestation or more (full-term group, n=35). Children born preterm had significantly lower scores than full-term controls on Performance IQ, Verbal IQ, receptive and expressive language skills, syntactic comprehension, linguistic processing speed, verbal memory, decoding, and reading comprehension but not on receptive vocabulary. Using MANCOVA, we found that SES, IQ, and prematurity all contributed to the variance in scores on a set of six non-overlapping measures of language and reading. Simple regression analyses found that after controlling for SES and Performance IQ, the degree of prematurity as measured by gestational age group was a significant predictor of linguistic processing speed, β=-.27, p<.05, R(2)=.07, verbal memory, β=.31, p<.05, R(2)=.09, and reading comprehension, β=.28, p<.05, R(2)=.08, but not of receptive vocabulary, syntactic comprehension, or decoding. The language and reading domains where prematurity had a direct effect can be classified as fluid as opposed to crystallized functions and should be monitored in school-aged children and adolescents born preterm.

Executive and memory function in adolescents born very preterm

BACKGROUND

Many preterm children display school difficulties, which may be mediated by impairment in executive function and memory.

OBJECTIVE

To evaluate executive and memory function among adolescents born preterm compared with term controls at 16 years.

METHODS

A total of 337 of 437 (77%) adolescents born in 1989 to 1992 with a birth weight < 1250 g and 102 term controls were assessed with a battery of executive function and memory tasks. Multiple regression analyses were used to compare groups and to identify associations between selected factors and outcomes among preterm subjects.

RESULTS

Adolescents born preterm, compared with term controls, showed deficits in executive function in the order of 0.4 to 0.6 SD on tasks of verbal fluency, inhibition, cognitive flexibility, planning/organization, and working memory as well as verbal and visuospatial memory. After exclusion of adolescents with neurosensory disabilities and full-scale IQ < 70, significant group differences persisted on most tests. Preterm subjects, compared with term controls, were at increased risk of exhibiting problems related to executive dysfunction, as measured with the Behavior Rating Inventory of Executive Function, on the Metacognition Index (odds ratio [OR]: 2.5 [95% confidence interval (CI): 1.2-5.1]) and the Global Executive Composite (OR: 4.2 [95% CI: 1.6-10.9]), but not on the Behavioral Regulation index (OR: 1.5 [95% CI: 0.7-3.5]). Among adolescents born preterm, severe brain injury on neonatal ultrasound and lower maternal education were the most consistent factors associated with poor outcomes.

CONCLUSIONS

Even after exclusion of preterm subjects with significant disabilities, adolescents born preterm in the early 1990s were at increased risk of deficits in executive function and memory.

Neurodevelopmental outcome of the premature infant

Advances in antenatal medicine and neonatal intensive care have successfully resulted in improved survival rates of preterm infants. These improvements have been most dramatic in infants born extremely low birth weight (ELBW, <or=1000 g) and at the limits of viability (22 to 25 weeks). But improvements in survival have not been accompanied by proportional reductions in the incidence of disability in this population. Thus, survival is not an adequate measure of success in these infants who remain at high risk for neurodevelopmental and behavioral morbidities. There is now increasing evidence of sustained adverse outcomes into school age and adolescence, not only for ELBW infants but for infants born late preterm.

The Color Object Association Test (COAT): the development of a new measure of declarative memory for 18- to 36-month-old toddlers

Few methods exist to measure declarative (explicit) memory in children during the toddler and preschool stages of development. We report the development and psychometric properties of a new measure of declarative memory for this age group, the Color Object Association Test (COAT). In pilot testing and large scale application of the test, the COAT was demonstrated to be a reliable and a valid measure of declarative memory for healthy children ages 18-36 months, living in a disadvantaged community. The test shows a linear developmental trajectory, which allows longitudinal examination of the development of declarative memory in children.

Process examination of executive function in ADHD: sex and subtype effects

To examine effects of group (Attention-Deficit/Hyperactivity Disorder [ADHD] versus Typically Developing [TD]), sex, and ADHD subtype on "process/optional" measures of executive functioning, children (n = 123; 54 ADHD, 69 TD) aged 8-16 completed subtests from the D-KEFS. No group, sex, or ADHD subtype effects were found on optional measures from the Trail Making, Color-Word Interference, and Tower tests. A significant interaction was found for Verbal Fluency Total Repetition Errors; boys with Combined/Hyperactive-Impulsive (ADHD-C/HI) type ADHD performed better than ADHD-C/HI girls, whereas girls with Inattentive type ADHD (ADHD-I) performed better than ADHD-I boys. Overall, children with ADHD did not differ from TD on most optional measures from the D-KEFS. When sex and ADHD subtype were considered, children with the subtype of ADHD less common for sex were at greater risk for poorer performance.

Cognitive and educational deficits in children born extremely preterm

A large body of research indicates that children born very preterm are at increased risk for neurobehavioral impairments; however, research examining outcome for extremely preterm (EP) children is limited. This chapter will review the literature focusing on early development delay, general intellectual functioning, specific cognitive skills, basic educational skills, and behavioral and emotional functioning in children born <26 weeks' gestation or with a birth weight <750 g. Findings are generally consistent and indicate that a large proportion of EP children and their families will face major challenges, including significant development delay, cognitive impairments, learning disabilities, and behavioral and emotional problems. However, a considerable proportion of these high-risk children will escape major impairments, and this variability in outcome is thought to be related to genetic (gender), perinatal (brain injury, bronchopulmonary dysplasia), and social-environmental (social risk, parenting) factors.

The Factor Structure of the CVLT-C in Pediatric Epilepsy

The current study used archival data to evaluate the fit of six latent variable models, originally generated by Donders (1999), for the California Verbal Learning Test-Children's Version (CVLT-C; Delis, Kramer, Kaplan, & Ober, 1994) in a large (N = 289) sample of pediatric epilepsy cases presenting at three tertiary treatment centers. Using confirmatory factor analysis, we found that a model including factors of Attention Span, Learning Efficiency, Free Delayed Recall, Cued Delayed Recall, and Inaccurate Recall demonstrated the best relative fit for our data. These findings are consistent with those reported by Donders (1999) in his reanalysis of the CVLT-C standardization sample data, supporting the validity of this factorial model in pediatric epilepsy populations.

Intellectual development in a Danish cohort of prematurely born preschool children: specific or general difficulties?

A national cohort of extremely low birth weight (ELBW) and/or extremely preterm (EPT) children and a term control group was followed up at the age of 5 years. The primary objective was to investigate whether premature birth had a global impact on cognitive functions or affected specific functions only. Assessment tools were Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R), Movement Assessment Battery for Children (M-ABC), and subtests from the Neuropsychological Assessment 4-7 years (NEPSY). The mean Full Scale IQ (FSIQ) and M-ABC score of the index children were 1.1 and 1.2 SDs lower than that of the control children (p <.001). Most WPPSI-R subtests showed medium to large differences between index and control children, suggesting a global impact of premature birth on cognitive functions. For both unadjusted and FSIQ adjusted means, no significant group differences on tests of memory or executive function were observed (p >.1), suggesting little impact of premature birth on these specific functions. In this sample, cognitive difficulties in 5-year-old ELBW and/or EPT children tended to be associated with general intellectual difficulties rather than with specific dysfunctions; however, the implications of this finding are ambiguous due to substantial attrition on the NEPSY subtests.

Neurodevelopmental outcome of bronchopulmonary dysplasia

Children born very preterm are vulnerable for long-term cognitive, educational, and behavioral impairments; bronchopulmonary dysplasia (BPD) is an additional risk factor which exacerbates these problems. As a population, children with BPD exhibit low average IQ, academic difficulties, delayed speech and language development, visual-motor integration impairments, and behavior problems. Neuropsychological studies are sparse, but there is some evidence that children with BPD also display attention problems, memory and learning deficits, and executive dysfunction. BPD does not appear to be associated with a specific neuropsychological impairment but rather a global impairment.

A controlled trial of skin-to-skin contact in extremely preterm infants

BACKGROUND

Extremely preterm birth, even in the absence of significant neurological impairment, is associated with altered pain responses and impaired memory and behaviour. Preterm birth increases the risk of maternal depression and may impede the development of the mother-infant relationship, factors that in turn are also associated with impaired infant outcome. Mother-infant skin-to-skin contact has been recommended as a simple means of ameliorating these effects.

METHODS

We conducted a pragmatic, prospective, controlled, intention-to-treat trial in two neonatal intensive care units. Infants born below 32 weeks gestation were recruited within the first week after birth and assigned to a control group receiving standard care, or an intervention group in which mothers were encouraged to provide a session of skin-to-skin contact once daily for 4 weeks. We assessed infant behaviour at time of discharge from hospital, responses to immunisation at 4 and 12 months of age, and memory, behaviour and development at 1 year corrected (postmenstrual) age. Indices of maternal depression, stress, anxiety, lactation performance and infant interaction were assessed at time of infant discharge, 4 months and 1 year.

RESULTS

No significant difference was identified in any infant or maternal measure at any time point.

CONCLUSIONS

Mother-infant skin-to-skin contact after extremely preterm birth results in neither benefit nor adverse consequences. Although there is no reason to dissuade mothers who wish to provide STS contact, we are unable to recommend resource allocation for the implementation of STS programmes for extremely preterm infants in a neonatal intensive care unit setting.

Neurodevelopmental follow-up after preterm birth: follow up after two years

Marked differences are seen in neurological and health status, intellectual functioning, school performance and behaviour between children born prematurely and those born at term. Assessment in later childhood has identified more subtle problems than the severe disability or sensory deficits readily identifiable at two years. These problems include learning disabilities, specific neuropsychological deficits in executive function, difficulties in visual-motor integration and perception, selective language impairment, motor coordination disorders, behaviour problems, attention deficit hyperactivity disorder (ADHD), and reduced educational achievement. Follow-up to school entry and beyond is thus required to determine the true prevalence and nature of the neurodevelopmental problems arising from preterm birth. Consensus about the assessment used, definitions of disability and health status, age of assessment and who undertakes it are necessary and should allow comparison across populations; this may help to maximise outcomes for children clearly at biological risk. Assessment of outcome for children born preterm beyond two years is required for counselling parents, planning health and education provision, for evaluation of services and to facilitate understanding of the longer term effects of preterm birth on brain development.

Executive control of learning and memory in children with bilateral spastic cerebral palsy

Executive control of learning and memory was examined in children with bilateral spastic cerebral palsy (SCP). We hypothesized that SCP-related brain damage would disrupt executive but not associative aspects of learning and memory. To test this hypothesis, the California Verbal Learning Test-Children's Version was administered to 16 children with bilateral SCP and 19 control children ranging from 6 to 18 years of age. Controlling for general verbal ability, the groups did not differ in initial learning and retention of information over time, suggesting that associative learning and memory processes subserved by medial temporal brain regions were relatively intact in children with SCP. In contrast, impairments in learning over repeated trials, strategic processing, and inhibition in the SCP group pointed to disruptions in prefrontally-mediated executive aspects of learning and memory. The inhibitory deficit was more pronounced in younger children with SCP, suggesting a developmental delay in this ability.

Learning disabilities in children with very low birthweight: prevalence, neuropsychological correlates, and educational interventions

This study examined achievement, neuropsychological, and intervention outcomes at a mean age of 11 years in children with very low birthweight (VLBW, <1500 g) compared with a term-born control group. To assess the prevalence and correlates of specific learning disabilities (LD), the sample was limited to children without neurosensory disorders who had at least low average IQ. Participants included 31 children with <750 g birthweight, 41 with 750-1499 g birthweight, and 52 controls. The <750 g group obtained lower scores in math, IQ, and perceptual-organizational skills than the term-born group. The < 750 g group also had higher rates of past and present LD than the controls. Despite these differences, the groups did not differ significantly in rates of special education or tutorial/remedial assistance. These findings suggest that children with extremely low birthweight without gross physical or intellectual impairments are at higher risk for LD and cognitive deficiencies than their term-born peers and that further efforts are needed to improve identification and treatment of these learning problems.

Long-term neuropsychological outcomes of very low birth weight: associations with early risks for periventricular brain insults

Few follow-up studies of children with very low birth weight (VLBW, <1,500 g) have examined neuropsychological sequelae at later ages or neonatal risks as predictors of these outcomes. The present study assessed cognitive skills at mean age 16 years in 48 participants with <750 g birth weight, 47 with 750-1,499 g birth weight, and 52 term-born controls. Our major objectives were to delineate the long-term cognitive consequences of VLBW, and to determine if risks for periventricular brain insults accounted for variations in outcomes. Analysis revealed poorer outcomes for the <750 g group than for term-born controls on nearly all measures, with specific impairments in visual-motor skills, spatial memory, and executive function. Predictors of outcome for participants with VLBW included lower birth weight, lower weight for gestational age, and a longer period of oxygen requirement for chronic lung disease. The longer-term consequences of VLBW are consistent with expectations based on early brain pathology and suggest limitations to functional plasticity.

Executive functioning in school-aged children who were born very preterm or with extremely low birth weight in the 1990s

OBJECTIVE

To determine the frequency, nature, and severity of executive dysfunction (EDF) at 8 years of age in extremely low birth weight (ELBW)/very preterm infants who were born in the 1990s, compared with normal birth weight (NBW) control subjects.

METHODS

A geographically determined cohort study was conducted in Victoria, Australia. The ELBW/very preterm cohort comprised 298 consecutive survivors at 2 years of age who had gestational ages <28 completed weeks or birth weights <1000 g and were born during 1991-1992. The NBW cohort comprised 262 randomly selected children of birth weight >2499 g matched on date of birth, gender, ethnicity, and health insurance status. The participation rate was 92% (275 of 298) for the ELBW/very preterm cohort and 85% (223 of 262) for the NBW cohort. Cognitive and behavioral measures of executive functioning were administered.

RESULTS

The ELBW/very preterm cohort exhibited significant EDF compared with their NBW peers in all areas assessed. The cognitive assessment revealed global impairment rather than deficits in specific executive domains. The ELBW/very preterm children also displayed more behavioral problems indicative of EDF than the NBW children. Severe impairments were exhibited in only a small minority of ELBW/very preterm children. No statistical conclusions were altered after adjustment for sociodemographic variables or when children with substantial neurosensory impairment were excluded.

CONCLUSIONS

School-aged children who were born in the 1990s and were very preterm or had ELBW are at greater risk for developing EDF and require ongoing neuropsychological review throughout middle childhood.

Longitudinal outcomes of very low birth weight: neuropsychological findings

To investigate the effects of very low birth weight (VLBW, &1500 g) on the development of neuropsychological skills, we assessed 67 children with birth weight <750 g, 64 with birth weight 750-1499 g, and 67 term-born controls. Growth modeling of raw scores from mean ages 7-14 years revealed persistent VLBW sequelae. Even when adjusting for IQ, the <750 g group scored more poorly than the term-born group on measures of language processing, verbal list learning, and perceptual-motor and organizational abilities. This group also made slower age-related progress than the control group on tests of perceptual-motor and executive functions. Environmental factors moderated group differences in change on other cognitive measures. These results revealed further evidence for slower skill development in both VLBW groups relative to controls, as well as"catch-up" growth in the 750-1499 g group on some measures. The findings suggest age-related changes in the cognitive sequelae of VLBW that depend on the skill assessed, the degree of VLBW, and environmental factors.

Evidence for unexpected weaknesses in learning in children with attention-deficit/hyperactivity disorder without reading disabilities

This study examined the mechanisms underlying verbal learning in children with and without attention-deficit/hyperactivity disorder (ADHD), none of whom had reading disabilities. Children with ADHD were compared to typically developing children on both process and product scores from the California Verbal Learning Test for Children. The findings indicated that children with ADHD initially learned the same number of words as controls but showed weaknesses recalling the words after delays, suggesting that children with ADHD are less efficient learners. Regardless of ADHD status, boys and girls performed differently. Boys used semantic clustering less frequently and recalled fewer words from the middle region of the list than girls; girls also outperformed boys in terms of overall performance, despite lower verbal IQ scores. These findings show that children with ADHD can exhibit unexpected weaknesses in learning even without a formal learning disability. Gender differences in verbal learning are also illustrated.

Facilitating infant adaptation: the nursery environment

The physical and social environment of the nursery is a direct and indirect influence on the development of premature infants. Qualities in the environment affect physiological stability and provide sensory experience that is relevant to brain development. Adaptation of the prematurely born infant to the unexpected surroundings of the neonatal intensive care unit can be facilitated when the infant's developmental needs are understood and characteristics of the environment are adapted accordingly. The need for environmental change is revealed by the infant's behaviour, that is, his interactions with the environment. The environment also affects the behaviour of caregivers, who like the baby need to be able to do their best in this challenging situation.