Aspects of inattention in low birth weight children

Inhibition abilities and functional brain connectivity in school-aged term-born and preterm-born children

BACKGROUND

Inhibition abilities are known to have impact on self-regulation, behavior, and academic success, and they are frequently impaired in children born preterm. We investigated the possible contributions of resting-state functional brain connectivity to inhibition following preterm birth.

METHODS

Forty-four preterm and 59 term-born participants aged 8-13 years were administered two inhibition tasks and resting-state functional MRI was performed. Functional connectivity (FC) networks were compared between groups using network-based statistics. Associations of FCNs and inhibition abilities were investigated through multivariate linear regression models accounting for the interaction between birth status and inhibition.

RESULTS

NBS revealed weaker FC in children born preterm compared to term-born peers in connections between motor and supplementary motor regions, frontal lobe, precuneus, and insula. Irrespective of birth status, connections between the cerebellum, frontal, and occipital lobes and inter-lobar, subcortical, intra-hemispheric long-range connections were positively correlated with one of the two inhibition tasks.

CONCLUSIONS

Preterm birth results in long-term alterations of FC at network level but these FCN alterations do not specifically account for inhibition problems in children born very preterm.

IMPACT

Irrespective of birth status, significant associations were found between the subdomain of response inhibition and functional connectivity in some subnetworks. A group comparisons of functional brain connectivity measured by rsfMRI in school-aged children born very preterm and at term. The investigation of network-level functional connectivity at rest does not appear adequate to explain differences in inhibition abilities between children born very preterm and at term, hence other imaging techniques might be more suited to explore the underlying neural mechanisms of inhibition abilities in school-aged children born very preterm.

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.

Inhibition is associated with whole-brain structural brain connectivity on network level in school-aged children born very preterm and at term

Inhibition abilities are often impaired in children born very preterm. In typically-developing individuals, inhibition has been associated with structural brain connectivity (SC). As SC is frequently altered following preterm birth, this study investigated whether aberrant SC underlies inhibition deficits in school-aged children born very preterm. In a group of 67 very preterm participants aged 8-13 years and 69 term-born peers, inhibition abilities were assessed with two tasks. In a subgroup of 50 very preterm and 62 term-born participants, diffusion tensor imaging (DTI) data were collected. Using network-based statistics (NBS), mean fractional anisotropy (FA_mean) was compared between groups. Associations of FA_mean and inhibition abilities were explored through linear regression. The composite score of inhibition abilities was lower in the very preterm group (M ​= ​-0.4, SD ​= ​0.8) than in the term-born group (M ​= ​0.0, SD ​= ​0.8) but group differences were not significant when adjusting for age, sex and socio-economic status (β ​= ​-0.13, 95%-CI [-0.30, 0.04], p ​= ​0.13). In the very preterm group, FA_mean was significantly lower in a network comprising thalamo-frontal, thalamo-temporal, frontal, cerebellar and intra-hemispheric connections than in the term-born group (t ​= ​5.21, lowest p-value ​= ​0.001). Irrespective of birth status, a network comprising parietal, cerebellar and subcortical connections was positively associated with inhibition abilities (t ​= ​4.23, lowest p-value ​= ​0.02). Very preterm birth results in long-term alterations of SC at network-level. As networks underlying inhibition abilities do not overlap with those differing between the groups, FA_mean may not be adequate to explain inhibition problems in very preterm children. Future studies should combine complementary measures of brain connectivity to address neural correlates of inhibition abilities.

Early life programming of attention capacity in adolescents: The HELENA study

The study aims to examine the individual and combined association of early life factors (birth weight, birth length, and any and exclusive breastfeeding) with attention capacity in adolescents. The study included 421 European adolescents (243 girls), aged 12.5-17.5 years, who participated in the Healthy Lifestyle in Europe by Nutrition in Adolescence Study. Body weight and length at birth of adolescents were collected from parental records. The duration of any and exclusive breastfeeding were self-reported. The d2 Test of Attention was administered to assess attention capacity. The main results showed that birth weight, birth length, breastfeeding, and exclusive breastfeeding were related to attention capacity in boys (β ranging from 0.144 to 0.196; all p < .05) after adjustment for age, centre, gestational age, maternal education, family affluence scale, and body mass index. Among boys, differences in attention capacity were found according to tertiles of birth weight and birth length (p < .05), as well as borderline significant differences across groups of any and exclusive breastfeeding (p = 0.055 and p = 0.108, respectively) after adjusting for potential confounders. In addition, boys with 3 early life risk factors (low birth weight, low birth length, and <3 months of breastfeeding) had significantly lower scores in attention capacity compared with boys with 0 risk factors (percentile score - 15.88; p = 0.009). In conclusion, early life factors, both separately and combined, may influence attention capacity in male European adolescents. Importantly, the combination of the 3 early life risk factors, low birth weight, low birth length, and <3 months of breastfeeding, even in normal ranges, may provide the highest reduction in attention capacity.

Sex differences in the association between foetal growth and child attention at age four: specific vulnerability of girls

BACKGROUND

Recent evidence suggests that impaired foetal growth may provide an early indication of increased risk of child attention problems. However, despite both foetal growth and child attention problems differing by sex, few studies have examined sex differences in this association. Furthermore, no studies have been conducted in low- and middle-income countries, where there are higher rates of perinatal problems. This study aimed to test for sex differences in the association between foetal growth indices and attention problems at age four, in a large, prospective birth cohort from a middle-income country.

METHODS

A total of 3,749 neonates from the 2004 Pelotas birth cohort (Brazil) with foetal growth indices collected at birth [low birthweight (LBW), small-for-gestational age (SGA), head circumference (HC), head circumference-to-abdominal circumference ratio (HC/AC) and ponderal index (PI)], were assessed for attention problems using the Child Behaviour Checklist at age four. Ordinal logistic regression with successive adjustment for maternal, demographic, gestational, perinatal and child nutrition/mother-child morbidity, was conducted separately for girls and boys.

RESULTS

In girls, attention difficulties were associated with being born SGA (OR = 1.40, CI = 1.08-1.82, p = .012), with a small HC (OR = 1.52, CI = 1.11-2.08, p = .009), or with a low PI (OR = 1.29, CI = 1.08-1.54, p = .005). There were no associations identified between attention difficulties and any foetal growth indices in boys.

CONCLUSIONS

Our results show that girls with impaired foetal growth may be particularly at risk of attention difficulties in childhood. This is consistent with emerging research that female foetuses may be more vulnerable to certain suboptimal intrauterine environments, inducing epigenetic changes that lead to disturbed growth and long-term developmental impairment.

Neural correlates of executive attention in adults born very preterm

Very preterm birth is associated with an increased prevalence of attention problems and may especially impair executive attention, i.e., top-down control of attentional selection in situations where distracting information interferes with the processing of task-relevant stimuli. While there are initial findings linking structural brain alterations in preterm-born individuals with attention problems, the functional basis of these problems are not well understood. The present study used an fMRI adaptation of the Attentional Network Test to examine the neural correlates of executive attention in a large sample of N = 86 adults born very preterm and/or with very low birth weight (VP/VLBW), and N = 100 term-born controls. Executive attention was measured by comparing task behavior and brain activations associated with the processing of incongruent vs. congruent arrow flanker stimuli. Consistent with subtle impairments of executive attention, the VP/VLBW group showed lower accuracy and a tendency for increased response times during the processing of incongruent stimuli. Both groups showed similar activation patters, especially within expected fronto-cingulo-parietal areas, but no significant between-group differences. Our results argue for a maintained attention-relevant network organization in high-functioning preterm born adults in spite of subtle deficits in executive attention. Gestational age and neonatal treatment variables showed associations with task behavior, and brain activation in the dorsal ACC and lateral occipital areas, suggesting that the degree of prematurity (and related neonatal complications) has subtle modulatory influences on executive attention processing.

•

fMRI study examines neural correlates of executive attention in preterm-born adults.

•

Preterm-born adults show subtle behavioral deficits.

•

Preterm-born adults show maintained organization of attention-related networks.

•

Modulatory effects of gestational age and neonatal treatment variables are observed.

Associations between birth weight, preeclampsia and cognitive functions in middle-aged adults

Both reductions in birth weight and preeclampsia (PE) have been associated with decrements in scores on tests of intelligence in children and adolescents. We examined whether these decrements persist into middle adulthood and expand into other domains of cognitive functioning. Using data from the Early Determinants of Adult Health project and from the ancillary project, Fetal Antecedents of Major Depression and Cardiovascular Disease, we selected term same-sex sibling sets or singletons from these sets, from the New England Family Study (NEFS) and the Child Health and Development Studies (CHDS), discordant on either fetal growth or PE, to test the hypotheses that prenatal exposure to inflammation was associated with decrements in attention, learning and executive function 40 years later. Exposure was defined as a continuous measure of percentile birth weight for gestational age, reduced fetal growth (<20th percentile of birth weight for gestational age) or maternal PE. Given that the sample was comprised, in part, of sibling sets, the analyses were performed using mixed models to account for the inter-sibling correlations. Analyses were performed separately by study site (i.e. NEFS and CHDS). We found few statistically significant associations (suggesting a possible type II error) consistent with previous literature, suggesting that the associations with low birth weight do not persist into midlife. We discuss the possible reasons for the lack of associations, which include the possible mediating effects of the postnatal environment.

Attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm/extremely low birth weight

The aim of this study was to evaluate attention difficulties in a contemporary geographic cohort of adolescents born extremely preterm (EP, <28 weeks' gestation) or extremely low birth weight (ELBW, birth weight <1000 g). The EP/ELBW group included 228 adolescents (mean age = 17.0 years) born in Victoria, Australia in 1991 and 1992. The control group were 166 adolescents (mean age = 17.4 years) born of normal birth weight (birth weight >2499 g) who were recruited in the newborn period and matched to the EP/ELBW group on date of birth, gender, language spoken and health insurance status. Participants were assessed on measures of selective, sustained, and executive (shift and divided) attention, and parents and participants completed behavioral reports. The EP/ELBW group performed more poorly across tests of selective and executive attention, had greater rates of clinically significant difficulties compared with the control group, and also had greater behavioral attention problems as reported by parents. Neonatal risk factors were weakly associated with attention outcomes. In conclusion, higher rates of attention impairments are observed in individuals born EP/ELBW well into adolescence and may have consequences for their transition to adulthood.

Executive function outcome in preterm adolescents

Preterm birth (PT) and low birthweight (LBW) are risk factors for cognitive, academic, and behavioral difficulties. Executive functioning, which is an umbrella term encompassing higher-order problem-solving and goal-oriented abilities, may help to understand these impairments. This review article examines executive functioning in PT and LBW children, with a specific focus on adolescence and the functional consequences of executive dysfunction in this age group. We have focused on adolescence as it is a critical period for brain, cognitive and social-emotional development, and a period of increased autonomy, independence and reliance on executive functioning. While more longitudinal research is required, there is evidence demonstrating that the PT/LBW population is at increased risk for impairments across all executive domains. Emerging evidence also suggests that executive dysfunction may partly explain poorer academic and social-emotional competence in PT/LBW adolescents. In conclusion, PT/LBW adolescents exhibit poorer executive functioning, and close surveillance is recommended for high-risk individuals.

Executive functions of children born very preterm--deficit or delay?

This cross-sectional study examined the performance of children born very preterm and/or at very low birth weight (VPT/VLBW) and same-aged term-born controls in three core executive functions: inhibition, working memory, and shifting. Children were divided into two age groups according to the median (young, 8.00-9.86 years; old, 9.87-12.99 years). The aims of the study were to investigate whether (a) VPT/VLBW children of both age groups performed poorer than controls (deficit hypothesis) or caught up with increasing age (delay hypothesis) and (b) whether VPT/VLBW children displayed a similar pattern of performance increase in executive functions with advancing age compared with the controls. Fifty-six VPT/VLBW children born in the cohort of 1998-2003 and 41 healthy-term-born controls were recruited. All children completed tests of inhibition (Color-Word Interference Task, Delis-Kaplan Executive Function System (D-KEFS)), working memory (Digit Span Backwards, HAWIK-IV), and shifting (Trail Making Test, Number-Letter Sequencing, D-KEFS). Results revealed that young VPT/VLBW children performed significantly poorer than the young controls in inhibition, working memory, and shifting, whereas old VPT/VLBW children performed similar to the old controls across all three executive functions. Furthermore, the frequencies of impairment in inhibition, working memory and shifting were higher in the young VPT/VLBW group compared with the young control group, whereas frequencies of impairment were equal in the old groups. In both VPT/VLBW children and controls, the highest increase in executive performance across the ages of 8 to 12 years was observed in shifting, followed by working memory, and inhibition.

CONCLUSIONS

This study provides evidence that (a) poor performance in inhibition, working memory, and shifting of young VPT/VLBW children might reflect a delay rather than a deficit and (b) that VPT/VLBW children are likely to display a similar pattern of performance increase in these three executive functions compared with that of controls.

Characteristics of Norwegian children suffering from ADHD symptoms: ADHD and primary health care

This study describes the characteristics of children suffering from attention deficit/hyperactivity disorder (ADHD) symptoms and evaluates the ability of primary health care to assess ADHD. A population of 494 children was referred during one year to the outpatient clinic Child and Adolescent Mental Health in Norway. Forty percent of those referred had ADHD symptoms. A clinical assessment regarding ADHD as well as general health was employed and socio-economic status was recorded. Half of the ADHD-referred children met criteria for ADHD, and among the non-ADHD children one fifth did not receive any diagnosis. Mean referral age was 10.5years; 82% were boys. The ADHD families were less educated and in more need of support from Child Welfare (CW) in the referral period (OR: 3.9; 95% CI 0.1 to 5.1). More ADHD children were not living with their families compared to the non-ADHD children. The sensitivity was 51% (96/187) regarding primary health care`s ability to recognize ADHD. Further screening programs for evaluation of ADHD are needed.

Basic Information Processing Abilities at 11 years Account for Deficits in IQ Associated with Preterm Birth

Although it is well established that preterms as a group do poorly relative to their full-term peers on tests of global cognitive functioning, the basis for this relative deficiency is less understood. The present paper examines preterm deficits in core cognitive abilities and determines their role in mediating preterm/full-term differences in IQ. The performance of 11-year-old children born preterm (birth weight <1750g) and their full-term controls were compared on a large battery of 15 tasks, covering four basic cognitive domains -- memory, attention, speed of processing and representational competence. The validity of these four domains was established using latent variables and confirmatory factor analysis (CFA). Preterms showed pervasive deficits within and across domains. Additionally, preterm deficits in IQ were completely mediated by these four cognitive domains in a structural equation model involving a cascade from elementary abilities (attention and speed), to more complex abilities (memory and representational competence), to IQ. The similarity of findings to those obtained with this cohort in infancy and toddlerhood suggest that preterm deficits persist - across time, across task, and from the non-verbal to the verbal period.

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.

Selectively reduced posterior corpus callosum size in a population-based sample of young adults born with low birth weight

BACKGROUND AND PURPOSE

Several studies suggest that VLBW is associated with a reduced CC size later in life. We aimed to clarify this in a prospective, controlled study of 19-year-olds, hypothesizing that those with LBWs had smaller subregions of CC than the age-matched controls, even after correcting for brain volume.

MATERIALS AND METHODS

One hundred thirteen survivors of LBW (BW <2000 grams) without major handicaps and 100 controls underwent a 3T MR examination of the brain. The cross-sectional area of the CC (total callosal area, and the callosal subregions of the genu, truncus, and posterior third) was measured. Callosal areas were adjusted for head size.

RESULTS

The posterior third subregion of the CC was significantly smaller in individuals born with a LBW compared with controls, even after adjusting for size of the forebrain. Individuals who were born with a LBW had a smaller CC (mean area, 553.4 mm(2)) than the controls (mean area, 584.1 mm(2)). Differences in total area, however, did not remain statistically significant after adjusting for FBV.

CONCLUSIONS

The uncorrected callosal size in 19-years-olds born with LBW was smaller than that of normal controls. However, after adjusting for FBV, the group difference was restricted to the posterior third. The clinical impact of a smaller posterior part needs further investigation.

Cerebral MRI and cognition in nonhandicapped, low birth weight adults

This study sought to compare cognitive and cerebral findings of magnetic resonance imaging in young adults with low birth weights and in a control group. One hundred thirteen of 173 (65%) eligible adults with birth weights <2000 g, and 100 of 170 (59%) controls, all without major disabilities, were examined at age 19 years. Cerebral 3.0 T magnetic resonance imaging was performed according to standardized protocols. Prorated intelligence quotient was estimated from two subtests of the Wechsler Abbreviated Scale of Ability, a word comprehension test, and matrices. Prominent lateral ventricles and loss of white matter, and thinning of the corpus callosum, were more common in the low birth weight group than in the control group (40% vs. 15%, respectively; odds ratio, 3.8; P < 0.001; and 31% vs. 7%, respectively; odds ratio, 6.0; P < 0.001). Low birth weight adults exhibited lower mean intelligence quotients (95 vs. 101, respectively; P < 0.001). Low birth weight adults face an increased risk of prominent ventricles, global loss of white matter, and thinning of the corpus callosum. Similar magnetic resonance imaging findings are not uncommon among healthy adults.

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.

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.

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.

Impact of neonatal thyroid hormone insufficiency and medical morbidity on infant neurodevelopment and attention following preterm birth

BACKGROUND

Infants born preterm are at risk of both transiently reduced thyroid hormone levels and impaired neurocognitive development, including attention deficits. The objective of this study was to examine the effects of reduced thyroid hormone levels on general neurodevelopment and attention at 3 months corrected age.

METHODS

Sixty-four infants born 24 to 35 weeks gestation were stratified into four gestational age groups: Group A, 23-26 weeks (n = 10); Group B, 27-29 weeks (n = 23); Group C, 30-32 weeks (n = 20); Group D, 33-35 weeks (n = 11). Controls were 33 healthy infants born full-term (Group E). In preterm only, free thyroxine (FT(4)), triiodothyronine (T(3)), and thyrotropin (TSH) were measured at 2 and 4 weeks of life and at 40 weeks postconceptional age. At 3 months corrected age, all infants were assessed with the Bayley Scales of Infant Development-Second Edition (BSID-II), from which both mental development index (MDI) and psychomotor development index (PDI) scores and four indices of attention were derived: sustained attention, selective attention, attention shift, and total attention.

RESULTS

Gestational age-stratified preterm groups differed significantly in T(3) and FT(4) levels at 2 and 4 weeks of life in infants born less than 27 weeks gestation. Preterm infants overall scored significantly below full-term on BSID-II MDI and PDI, selective, sustained, and total attention scales. In the preterm group, FT(4) levels were positively associated with PDI and selective, sustained, and total attention.

CONCLUSIONS

Reduced levels of thyroid hormone in the neonatal period in preterm infants are associated with a reduced neurocognitive outcome in the attention domain at 3 months corrected age.

The role of transient hypothyroxinemia of prematurity in development of visual abilities

Preterm birth is associated with an increased risk of visual impairment. However, not all visual deficits can be fully explained by the typical prematurity morbidity factors. In addition, children born preterm often exhibit transient hypothroxinemia of prematurity (THOP) due to premature severing of the maternal supply of thyroid hormones. Because thyroid hormone is critically needed for multiple facets of early brain development, including the structures needed for visual processing, and because the maternal thyroid supply is essential throughout pregnancy, it is possible that THOP contributes to the visual impairments seen in preterm children. To test this hypothesis, we used both clinical tests and visual-evoked potential techniques to assess visual abilities in two cohorts of preterm infants whose thyroid hormone levels were measured in the perinatal period. In the first cohort born 30 to 35 weeks gestation, we found associations between low thyroid hormone levels and reduced visual attention at 3 months corrected age (Study 1) and poor visuomotor abilities at 12 and 18 months corrected age (Study 2). In the second cohort born 23 to 35 weeks gestation, THOP severity was negatively correlated with attention at 3 months corrected age (Study 3) and contrast sensitivity and color vision at 6 months corrected age (Study 4). These findings therefore suggest that thyroid hormone is necessary for the development of early visual abilities and that THOP may partially explain the visual deficits of preterm infants.

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.

Attention problems in very low birth weight preschoolers: are new screening measures needed for this special population?

PROBLEM

Children born prematurely have been shown to have a range of problems that often result in delayed academic achievement.

METHODS

The current study assessed both attention problem scores (Child Behavior Checklist) and actual performance on tasks tapping three attention networks in a sample of children (n = 94) born with very low birth weights (VLBW; < or = 1500 grams).

FINDINGS

Attention problem scores were extremely low and did not predict children's actual attention performance.

CONCLUSIONS

A body of research is developing that suggests VLBW children may have specific, yet subtle, attention problems that may differ from those of other children.

Attention deficit disorders: are we barking up the wrong tree?

Attention deficit disorder (AAD) and attention deficit/hyperactivity disorder (ADHD) are very frequent and protean developmental disorders without a definite biologic marker. This review proposes a framework to understand the enlarged spectrum of its manifestations based on current knowledge of the mechanisms underlying arousal and attention variations during sleep/wake cycle. The neuro-modulation's pivotal role in this process as well as in the fine tuning of synaptic architecture during development must be taken into account when trying to understand the marked fuzziness of the symptoms and the very high prevalence of reported co-morbidities. The series of related interactions includes a cyclic deactivation of the dorso-lateral portion of the prefrontal cortex (DLPFC) during sleep, suspending executive functions, co-occurring with rhythmic periods of decreased noradrenergic tonus. A protracted unbalance in modulation, with catecholaminergic relative deficiency, could explain less-than-optimum waking DLPFC activation and the most important manifestations of ADD. Beside the well documented dopaminergic effects of stimulant medication used in ADD and ADHD, a more important role must be assigned to noradrenaline (NA). At this light hyperactivity and impulsivity are less important dimensions. Rather, an attention deficit spectrum disorder should probably be regarded as a complication of a core defect in prefrontal cortex dependent inhibitory control, underlying inattention.