Hippocampal volume and everyday memory in children of very low birth weight

Thalamic alterations in preterm neonates and their relation to ventral striatum disturbances revealed by a combined shape and pose analysis

Finding the neuroanatomical correlates of prematurity is vital to understanding which structures are affected, and to designing efficient prevention and treatment strategies. Converging results reveal that thalamic abnormalities are important indicators of prematurity. However, little is known about the localization of the abnormalities within the subnuclei of the thalamus, or on the association of altered thalamic development with other deep gray matter disturbances. Here, we aim to investigate the effect of prematurity on the thalamus and the putamen in the neonatal brain, and further investigate the associated abnormalities between these two structures. Using brain structural magnetic resonance imaging, we perform a novel combined shape and pose analysis of the thalamus and putamen between 17 preterm (41.12 ± 5.08 weeks) and 19 term-born (45.51 ± 5.40 weeks) neonates at term equivalent age. We also perform a set of correlation analyses between the thalamus and the putamen, based on the surface and pose results. We locate significant alterations on specific surface regions such as the anterior and ventral anterior (VA) thalamic nuclei, and significant relative pose changes of the left thalamus and the right putamen. In addition, we detect significant association between the thalamus and the putamen for both surface and pose parameters. The regions that are significantly associated include the VA, and the anterior and inferior putamen. We detect statistically significant surface deformations and pose changes on the thalamus and putamen, and for the first time, demonstrate the feasibility of using relative pose parameters as indicators for prematurity in neonates. Our methods show that regional abnormalities of the thalamus are associated with alterations of the putamen, possibly due to disturbed development of shared pre-frontal connectivity. More specifically, the significantly correlated regions in these two structures point to frontal-subcortical pathways including the dorsolateral prefrontal-subcortical circuit, the lateral orbitofrontal-subcortical circuit, the motor circuit, and the oculomotor circuit. These findings reveal new insight into potential subcortical structural covariates for poor neurodevelopmental outcomes in the preterm population.

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.

Does vitamin C deficiency affect cognitive development and function?

Vitamin C is a pivotal antioxidant in the brain and has been reported to have numerous functions, including reactive oxygen species scavenging, neuromodulation, and involvement in angiogenesis. Absence of vitamin C in the brain has been shown to be detrimental to survival in newborn SVCT2(−/−) mice and perinatal deficiency have shown to reduce hippocampal volume and neuron number and cause decreased spatial cognition in guinea pigs, suggesting that maternal vitamin C deficiency could have severe consequences for the offspring. Furthermore, vitamin C deficiency has been proposed to play a role in age-related cognitive decline and in stroke risk and severity. The present review discusses the available literature on effects of vitamin C deficiency on the developing and aging brain with particular focus on in vivo experimentation and clinical studies.

Brain volumes and cognitive function in very-low-birth-weight (VLBW) young adults

BACKGROUND

Preterm born very-low-birth-weight (VLBW: birth weight ≤1500 g) survivors have increased risk of perinatal brain injury that may cause deviant brain development and later neuroimpairments, including reduced cognitive functioning.

AIMS

In this long-term follow up study of three year-cohorts (birth years 1986-88) of VLBW subjects and term born controls with normal birth weight, the aim was to examine differences in brain volumes at age 20 years. In addition, the relationships between brain volumes and cognitive abilities and perinatal variables were explored.

METHODS

Forty-four VLBW subjects and 60 controls were assessed with cognitive testing (Wechsler Adult Intelligence Scale - WAIS-III) and structural MRI at 1.5 T, using the FreeSurfer 5.1 software for volumetric analysis. A subpopulation had MRI performed also at age 15, and for this group changes in brain volumes with age were examined.

RESULTS

The VLBW subjects had smaller brain volumes, especially of thalamus, globus pallidus and parts of the corpus callosum, and larger lateral ventricles than controls at age 20. However, no significant group differences in longitudinal change from age 15 to 20 were observed. The most immature and smallest VLBW subjects at birth, and those with the highest perinatal morbidity, showed most pronounced volume deviations. Positive associations between several brain volumes and full IQ, as well as three of four IQ indices in the VLBW group, were observed.

CONCLUSION

Reduced volumes of grey and white matter and ventricular dilatation in VLBW young adults may indicate permanent effects on brain development from perinatal brain injury with influence on later cognitive function.

Posttraumatic feeding disorder in low birth weight young children: a nested case-control study of a home-based intervention program

Low birth weight infants (LBW) are reported to be at risk for posttraumatic feeding disorder (PTFD). In this study, we evaluated the outcome of an intervention program for infants with PTFD. LBW infants with PTFD (N=21) completed feeding behavior questionnaires at entry and after completing the program and were compared to a matched control group. PTFD group infants showed a significantly high rate of food disorder symptoms at entry but not at follow-up compared to the control group. The intervention program for PTFD infants resulted in reduced feeding disorder symptoms.

Neural compensation in adulthood following very preterm birth demonstrated during a visual paired associates learning task

Very preterm birth (VPT; < 33 weeks of gestation) is associated with an increased risk of learning disability, which contributes to more VPT-born children repeating grades and underachieving in school. Learning problems associated with VPT birth may be caused by pathophysiological alterations in neurodevelopment resulting from perinatal brain insult; however, adaptive neuroplastic processes may subsequently occur in the developing preterm brain which ameliorate, to an extent, the potential sequelae of altered neurophysiology. Here, we used functional magnetic resonance imaging (fMRI) to compare neuronal activation in 24 VPT individuals and 22 controls (CT) in young adulthood during a learning task consisting of the encoding and subsequent recognition of repeated visual paired associates. Structural MRI data were also collected and analysed in order to explore possible structure-function associations. Whilst the two groups did not differ in their learning ability, as demonstrated by their capacity to recognize previously-seen and previously-unseen visual pairs, between-group differences in linear patterns of Blood Oxygenation Level Dependant (BOLD) activity were observed across the four repeated blocks of the task for both the encoding and recognition conditions, suggesting that the way learning takes place differs between the two groups. During encoding, significant between-group differences in patterns of BOLD activity were seen in clusters centred on the cerebellum, the anterior cingulate gyrus, the midbrain/substantia nigra, medial temporal (including parahippocampal) gyrus and inferior and superior frontal gyri. During the recognition condition, significant between-group differences in patterns of BOLD activity were seen in clusters centred on the claustrum and the posterior cerebellum. Structural analysis revealed smaller grey matter volume in right middle temporal gyrus in VPT individuals compared to controls, however volume in this region was not significantly associated with functional activation. These results demonstrate that although cognitive task performance between VPT individuals and controls may be comparable on certain measures, differences in BOLD signal may also be evident, some of which could represent compensatory neural processes following VPT-related brain insult.

Longitudinal growth and morphology of the hippocampus through childhood: Impact of prematurity and implications for memory and learning

The effects of prematurity on hippocampal development through early childhood are largely unknown. The aims of this study were to (1) compare the shape of the very preterm (VPT) hippocampus to that of full-term (FT) children at 7 years of age, and determine if hippocampal shape is associated with memory and learning impairment in VPT children, (2) compare change in shape and volume of the hippocampi from term-equivalent to 7 years of age between VPT and FT children, and determine if development of the hippocampi over time predicts memory and learning impairment in VPT children. T1 and T2 magnetic resonance images were acquired at both term equivalent and 7 years of age in 125 VPT and 25 FT children. Hippocampi were manually segmented and shape was characterized by boundary point distribution models at both time-points. Memory and learning outcomes were measured at 7 years of age. The VPT group demonstrated less hippocampal infolding than the FT group at 7 years. Hippocampal growth between infancy and 7 years was less in the VPT compared with the FT group, but the change in shape was similar between groups. There was little evidence that the measures of hippocampal development were related to memory and learning impairments in the VPT group. This study suggests that the developmental trajectory of the human hippocampus is altered in VPT children, but this does not predict memory and learning impairment. Further research is required to elucidate the mechanisms for memory and learning difficulties in VPT children.

Neurodevelopmental outcomes of infants born prematurely

Long-term follow-up of infants born prematurely is necessary to determine neurodevelopmental outcomes, particularly with the expansion of interest from major disabilities to high prevalence/low severity dysfunctions. Models of pathogenesis include changes due to developmental disruptions and to injury, the magnitude and type of change influenced by the infant's age, and central nervous system recovery and reorganization. Alterations in neurogenesis, migration, myelination, cell death, and synaptogenesis occur even in the absence of insult. Despite increased knowledge regarding these processes, the functional significance of brain abnormalities is unclear. Because of methodologic problems in follow-up studies, it is difficult to characterize outcome definitively. Nonetheless, an acceptable degree of agreement across studies is found with regard to specific neurodevelopmental outcomes: motor/neurologic function, visuomotor integrative skills, IQ, academic achievement, language, executive function, and attention-deficit hyperactivity disorder/behavioral issues. In general, children born prematurely have more problems in these areas than do their normal birth weight counterparts. Suggestions for improved analyses and clarification of outcomes include use of cluster analysis, structural equation modeling, growth curve analysis, developmental epidemiologic approaches, and better control of background variables using risk indexes and factor scores. Better assessment techniques measuring functions documented to be at higher risk of problems are discussed.

Social attribution skills of children born preterm at very low birth weight

Children born prematurely at very low birth weight (<1500 g) are at increased risk for impairments affecting social functioning, including autism spectrum disorders (e.g., Johnson et al., 2010). In the current study, we used the Happé-Frith animated triangles task (Abell, Happé, & Frith, 2000) to study social attribution skills in this population. In this task, typical viewers attribute intentionality and mental states to shapes, based on characteristics of their movements. Participants included 34 preterm children and 36 full-term controls, aged 8-11 years. Groups were comparable in terms of age at test, gender, handedness, and socioeconomic status; they also performed similarly on tests of selective attention/processing speed and verbal intelligence. Relative to full-term peers, preterm children's descriptions of the animations were less appropriate overall; they also overattributed intentionality/mental states to randomly moving shapes and underattributed intentionality/mental states to shapes that seemed to be interacting socially. Impairments in the ability to infer the putative mental states of triangles from movement cues alone were most evident in children displaying more "autistic-like" traits, and this may reflect atypical development of and/or functioning in, or atypical connections between, parts of the social brain.

A neonatal piglet model for investigating brain and cognitive development in small for gestational age human infants

The piglet was investigated as a potential model for studying brain and cognitive deficits associated with being born small for gestational age (SGA). Naturally farrowed SGA (0.7-1.0 kg BW) and average for gestational age (AGA, 1.3-1.6 kg BW) piglets were obtained on postnatal day (PD) 2, placed in individual cages, and provided a nutritionally adequate milk replacer diet (285 ml/kg/d). Beginning at PD14, performance in a spatial T-maze task was assessed. At PD28, piglets were anesthetized for magnetic resonance (MR) imaging to assess brain structure (voxel-based morphometry), connectivity (diffusion-tensor imaging) and metabolites in the hippocampus and corpus callosum (proton MR spectroscopy). Piglets born SGA showed compensatory growth such that BW of SGA and AGA piglets was similar (P>0.05), by PD15. Birth weight affected maze performance, with SGA piglets taking longer to reach criterion than AGA piglets (p<0.01). Total brain volume of SGA and AGA piglets was similar (P<0.05), but overall, SGA piglets had less gray matter than AGA piglets (p<0.01) and tended to have a smaller internal capsule (p = 0.07). Group comparisons between SGA and AGA piglets defined 9 areas (≥ 20 clusters) where SGA piglets had less white matter (p<0.01); 2 areas where SGA piglets had more white matter (p<0.01); and 3 areas where SGA piglets had more gray matter (p<0.01). The impact of being born SGA on white matter was supported by a lower (p<0.04) fractional anisotropy value for SGA piglets, suggesting reduced white matter development and connectivity. None of the metabolites measured were different between groups. Collectively, the results show that SGA piglets have spatial learning deficits and abnormal development of white matter. As learning deficits and abnormalities in white matter are common in SGA human infants, the piglet is a tractable translational model that can be used to investigate SGA-associated cognitive deficits and potential interventions.

Effects of maternal hypothyroidism on offspring hippocampus and memory

BACKGROUND

Rodents with gestational thyroid-hormone (TH) deficiencies and children with congenital hypothyroidism show abnormal hippocampal development. Given that the human hippocampus starts to develop early in gestation, we asked if children born to women with hypothyroidism during pregnancy also show hippocampal abnormalities and if this is related to the severity of maternal TH insufficiency and current memory functioning. We additionally sought to determine whether effects were more prominent in anterior or posterior hippocampal subsections given these support different memory functions and have different developmental trajectories. We hypothesized that these children would have smaller than normal hippocampal volumes than controls and show memory deficits on both standardized tests and indices of "everyday" memory functioning.

METHODS

We studied 54 children aged 9 to 12 years: 30 controls and 24 HYPO cases-offspring from women diagnosed with hypothyroidism prior to or during pregnancy and treated with l-thyroxine. All children received a thorough assessment of memory functions and an MRI scan. For each child, right and left hippocampi were manually traced, and volumes of right and left hippocampi and anterior and posterior segments were determined.

RESULTS

HYPO cases showed significantly smaller right and left hippocampal volumes than controls, particularly in right posterior and left anterior segments. In HYPO children, hippocampal volumes were negatively correlated with maternal third-trimester TSH levels and positively correlated with third-trimester fT4. HYPO cases scored significantly below controls on one objective and several subjective memory indices, and these were correlated with hippocampal volumes.

CONCLUSION

Early TH insufficiency from maternal hypothyroidism affects offspring hippocampal development and memory.

Chronic allopurinol treatment during the last trimester of pregnancy in sows: effects on low and normal birth weight offspring

Low-birth-weight (LBW) children are born with several risk factors for disease, morbidity and neonatal mortality, even if carried to term. Placental insufficiency leading to hypoxemia and reduced nutritional supply is the main cause for LBW. Brain damage and poor neurological outcome can be the consequence. LBW after being carried to term gives better chances for survival, but these children are still at risk for poor health and the development of cognitive impairments. Preventive therapies are not yet available. We studied the risk/efficacy of chronic prenatal treatment with the anti-oxidative drug allopurinol, as putative preventive treatment in piglets. LBW piglets served as a natural model for LBW. A cognitive holeboard test was applied to study the learning and memory abilities of these allopurinol treated piglets after weaning. Preliminary analysis of the plasma concentrations in sows and their piglets suggested that a daily dose of 15 mg.kg(-1) resulted in effective plasma concentration of allopurinol in piglets. No adverse effects of chronic allopurinol treatment were found on farrowing, birth weight, open field behavior, learning abilities, relative brain, hippocampus and spleen weights. LBW piglets showed increased anxiety levels in an open field test, but cognitive performance was not affected by allopurinol treatment. LBW animals treated with allopurinol showed the largest postnatal compensatory body weight gain. In contrast to a previous study, no differences in learning abilities were found between LBW and normal-birth-weight piglets. This discrepancy might be attributable to experimental differences. Our results indicate that chronic prenatal allopurinol treatment during the third trimester of pregnancy is safe, as no adverse side effects were observed. Compensatory weight gain of treated piglets is a positive indication for the chronic prenatal use of allopurinol in these animals. Further studies are needed to assess the possible preventive effects of allopurinol on brain functions in LBW piglets.

Bigger is better and worse: on the intricate relationship between hippocampal size and memory

The structure-function relationship between the hippocampal region and memory is a debated topic in the literature. It has been suggested that larger hippocampi are associated with less effective memory performance in healthy young adults because of a partial synaptic pruning. Here, we tested this hypothesis in individuals with Fragile X Syndrome (FXS) with known abnormal pruning and IQ- and age-matched individuals with hypoxic brain injury, preterm birth, and obstetric complications. Results revealed larger normalized hippocampal volume in FXS compared with neurotypical controls, whereas individuals with hypoxic injury had smaller hippocampi. In neurotypical controls and individuals with hypoxic injury, better general memory, as indexed by the Wechsler Memory Scale-Revised, was associated with larger hippocampus. In contrast, in FXS we observed the opposite relationship: larger hippocampus was associated with worse general memory. Caudate volume did not correlate with memory in either group. These results suggest that incomplete pruning in young healthy adults may not contribute to less efficient memory capacity, and hippocampal size is positively associated with memory performance. However, abnormally large and poorly pruned hippocampus may indeed be less effective in FXS.

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.

Neuropathologic studies of the encephalopathy of prematurity in the late preterm infant

It has been widely suggested that brain damage in survivors of late preterm deliveries is similar to that in early preterm infants, only less severe. This report addresses this concept through reanalysis of published neuropathologic data obtained according to late preterm in comparison with early preterm ages. Findings suggest that the spectrum of brain injury in the late preterm infant, as determined in an autopsy population, is similar to that found in early preterm infants, with potential differential susceptibility for different neuronal, glial, and vascular indices. Further research is needed to more clearly define developmental cellular susceptibilities in preterm populations.

The relationship between hippocampal asymmetry and temperament in adolescent borderline and antisocial personality pathology

Investigating etiological processes early in the life span represents an important step toward a better understanding of the development of personality pathology. The current study evaluated the interaction between an individual difference risk factor (i.e., temperament) and a biological risk factor for aggressive behavior (i.e., atypical [larger] rightward hippocampal asymmetry) in predicting the emergence of borderline personality disorder (BPD) and antisocial personality disorder symptoms during early adolescence. The sample consisted of 153 healthy adolescents (M = 12.6 years, SD = 0.4, range = 11.4–13.7) who were selected from a larger sample to maximize variation in temperament. Interactions between four temperament factors (effortful control, negative affectivity, surgency, and affiliativeness), based on the Early Adolescent Temperament Questionnaire—Revised, and volumetric measures of hippocampal asymmetry were examined as cross-sectional predictors of BPD and antisocial personality disorder symptoms. Boys were more likely to have elevated BPD symptoms if they were high on affiliation and had larger rightward hippocampal asymmetry. In boys, low affiliation was a significant predictor of BPD symptoms in the presence of low rightward hippocampal asymmetry. For girls, low effortful control was associated with elevated BPD symptoms in the presence of atypical rightward hippocampal asymmetry. This study builds on previous work reporting significant associations between atypical hippocampal asymmetry and poor behavioral regulation.

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.

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.

Structural and functional brain correlates of behavioral outcomes during adolescence

Several studies have described an association between very preterm birth and behavioral and psychiatric outcomes in childhood and adolescence. The exact mechanisms underlying this association are unknown, but impaired neurodevelopment has been proposed as a possible etiological factor. Existing research suggests a selective vulnerability of brain regions associated with a variety of behavioral and psychiatric outcomes following very preterm birth. This article reviews studies that have directly explored the structural and functional brain correlates of behavioral outcomes in ex-preterm individuals, with an emphasis on attentional problems, overall mental health functioning including internalizing and externalizing scores, and psychosocial adjustment. The focus here is on neuroimaging research conducted during adolescence, a period of life associated with the emergence and early expression of several psychiatric disorders. The neurodevelopmental hypothesis is used as a theoretical framework, according to which early brain lesions interact with the developing brain to increase later vulnerability to psychopathology.

Cerebral inflammation and mobilization of the peripheral immune system following global hypoxia-ischemia in preterm sheep

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most important causes of brain injury in preterm infants. Preterm HIE is predominantly caused by global hypoxia-ischemia (HI). In contrast, focal ischemia is most common in the adult brain and known to result in cerebral inflammation and activation of the peripheral immune system. These inflammatory responses are considered to play an important role in the adverse outcomes following brain ischemia. In this study, we hypothesize that cerebral and peripheral immune activation is also involved in preterm brain injury after global HI.

METHODS

Preterm instrumented fetal sheep were exposed to 25 minutes of umbilical cord occlusion (UCO) (n = 8) at 0.7 gestation. Sham-treated animals (n = 8) were used as a control group. Brain sections were stained for ionized calcium binding adaptor molecule 1 (IBA-1) to investigate microglial proliferation and activation. The peripheral immune system was studied by assessment of circulating white blood cell counts, cellular changes of the spleen and influx of peripheral immune cells (MPO-positive neutrophils) into the brain. Pre-oligodendrocytes (preOLs) and myelin basic protein (MBP) were detected to determine white matter injury. Electro-encephalography (EEG) was recorded to assess functional impairment by interburst interval (IBI) length analysis.

RESULTS

Global HI resulted in profound activation and proliferation of microglia in the hippocampus, periventricular and subcortical white matter. In addition, non-preferential mobilization of white blood cells into the circulation was observed within 1 day after global HI and a significant influx of neutrophils into the brain was detected 7 days after the global HI insult. Furthermore, global HI resulted in marked involution of the spleen, which could not be explained by increased splenic apoptosis. In concordance with cerebral inflammation, global HI induced severe brain atrophy, region-specific preOL vulnerability, hypomyelination and persistent suppressed brain function.

CONCLUSIONS

Our data provided evidence that global HI in preterm ovine fetuses resulted in profound cerebral inflammation and mobilization of the peripheral innate immune system. These inflammatory responses were paralleled by marked injury and functional loss of the preterm brain. Further understanding of the interplay between preterm brain inflammation and activation of the peripheral immune system following global HI will contribute to the development of future therapeutic interventions in preterm HIE.

Maternal vitamin C deficiency during pregnancy persistently impairs hippocampal neurogenesis in offspring of guinea pigs

While having the highest vitamin C (VitC) concentrations in the body, specific functions of VitC in the brain have only recently been acknowledged. We have shown that postnatal VitC deficiency in guinea pigs causes impairment of hippocampal memory function and leads to 30% less neurons. This study investigates how prenatal VitC deficiency affects postnatal hippocampal development and if any such effect can be reversed by postnatal VitC repletion. Eighty pregnant Dunkin Hartley guinea pig dams were randomized into weight stratified groups receiving High (900 mg) or Low (100 mg) VitC per kg diet. Newborn pups (n = 157) were randomized into a total of four postnatal feeding regimens: High/High (Control); High/Low (Depleted), Low/Low (Deficient); and Low/High (Repleted). Proliferation and migration of newborn cells in the dentate gyrus was assessed by BrdU labeling and hippocampal volumes were determined by stereology. Prenatal VitC deficiency resulted in a significant reduction in postnatal hippocampal volume (P<0.001) which was not reversed by postnatal repletion. There was no difference in postnatal cellular proliferation and survival rates in the hippocampus between dietary groups, however, migration of newborn cells into the granular layer of the hippocampus dentate gyrus was significantly reduced in prenatally deficient animals (P<0.01). We conclude that a prenatal VitC deficiency in guinea pigs leads to persistent impairment of postnatal hippocampal development which is not alleviated by postnatal repletion. Our findings place attention on a yet unrecognized consequence of marginal VitC deficiency during pregnancy.

Modeling the encephalopathy of prematurity in animals: the important role of translational research

Translational research in preterm brain injury depends upon the delineation of the human neuropathology in order that animal models faithfully reiterate it, thereby ensuring direct relevance to the human condition. The major substrate of human preterm brain injury is the encephalopathy of prematurity that is characterized by gray and white matter lesions reflecting combined acquired insults, altered developmental trajectories, and reparative phenomena. Here we highlight the key features of human preterm brain development and the encephalopathy of prematurity that are critical for modeling in animals. The complete mimicry of the complex human neuropathology is difficult in animal models. Many models focus upon mechanisms related to a specific feature, for example, loss of premyelinating oligodendrocytes in the cerebral white matter. Nevertheless, animal models that simultaneously address oligodendrocyte, neuronal, and axonal injury carry the potential to decipher shared mechanisms and synergistic treatments to ameliorate the global consequences of the encephalopathy of prematurity.

Neuroanatomical consequences of very preterm birth in middle childhood

Individuals born preterm can demonstrate reductions in brain volume, cortical surface area and thickness. However, the extent of these neuroanatomical deficits and the relation among these measures in middle childhood, a critical developmental period, have not been determined. We assessed differences in brain structure by acquiring high-resolution T(1)-weighted scans in 25 children born very preterm (<32 weeks gestational age) without significant post-natal neurological sequelae and 32 age-matched term-born children (7-10 years). Children born very preterm had decreased brain volume, surface area and cortical thickness compared to term-born children. Furthermore, children born preterm did not display the robust relation between total brain volume and basal ganglia and thalamic volume apparent in the term-born children. Cortical thickness analyses revealed that the cortex was thinner for children born preterm than term-born children in the anterior cingulate cortex/supplementary motor area, isthmus of the cingulate gyrus, right superior temporal sulcus, right anterior insula, postcentral gyrus and precuneus. Follow-up analyses revealed that right precuneus thickness was correlated with gestational age. Thus, even without significant postnatal medical sequelae, very preterm-born children showed atypical brain structure and developmental patterns in areas related to higher cognitive function. Disruptions of the typical neurodevelopmental trajectory in the third trimester of pregnancy likely underlie these differences persisting into middle childhood.

Neonatal brain injury and neuroanatomy of memory processing following very preterm birth in adulthood: an fMRI study

Altered functional neuroanatomy of high-order cognitive processing has been described in very preterm individuals (born before 33 weeks of gestation; VPT) compared to controls in childhood and adolescence. However, VPT birth may be accompanied by different types of adverse neonatal events and associated brain injury, the severity of which may have differential effects on brain development and subsequent neurodevelopmental outcome. We conducted a functional magnetic resonance imaging (fMRI) study to investigate how differing degrees of neonatal brain injury, detected by neonatal ultrasounds, affect the functional neuroanatomy of memory processing in VPT young adults. We used a verbal paired associates learning task, consisting of four encoding, four cued-recall and four baseline condition blocks. To further investigate whether differences in neural activation between the groups were modulated by structural brain changes, structural MRI data were also collected. We studied 12 VPT young adults with a history of periventricular haemorrhage with associated ventricular dilatation, 17 VPT individuals with a history of uncomplicated periventricular haemorrhage, 12 individuals with normal ultrasonographic findings, and 17 controls. Results of a linear trend analysis demonstrated that during completion of the paired associates learning task right frontal and right parietal brain activation decreased as the severity of neonatal brain injury increased. There were no statistically significant between-group differences in on-line task performance and participants' intelligence quotient (IQ) at assessment. This pattern of differential activation across the groups was observed particularly in the right middle frontal gyrus during encoding and in the right posterior cingulate gyrus during recall. Structural MRI data analysis revealed that grey matter volume in the right superior temporal gyrus, right cerebellum, left middle temporal gyrus, right globus pallidus and right medial frontal gyrus decreased with increasing severity of neonatal brain injury. However, the significant between-group functional neuroanatomical differences were not directly attributable to the detected structural regional differences.

Evidence-based neonatal pharmacotherapy: postnatal corticosteroids

Corticosteroids are used in the neonatal intensive care unit primarily to treat two conditions: bronchopulmonary dysplasia (BPD) and hypotension (cardiovascular insufficiency). Historically, high-dose dexamethasone was used for BPD, but its use was later associated with adverse neurodevelopmental outcomes and decreased substantially. Data from randomized controlled trials regarding efficacy and safety of lower-dose dexamethasone therapy are insufficient to recommend its use. Hydrocortisone may be an alternative to dexamethasone, but again data are insufficient to support use. Hydrocortisone therapy is increasingly used to treat hypotension in critically ill newborns; however, the outcomes of this therapy must be evaluated in randomized trials.

A lifespan approach to neuroinflammatory and cognitive disorders: a critical role for glia

Cognitive decline is a common problem of aging. Whereas multiple neural and glial mechanisms may account for these declines, microglial sensitization and/or dystrophy has emerged as a leading culprit in brain aging and dysfunction. However, glial activation is consistently observed in normal brain aging as well, independent of frank neuroinflammation or functional impairment. Such variability suggests the existence of additional vulnerability factors that can impact neuronal-glial interactions and thus overall brain and cognitive health. The goal of this review is to elucidate our working hypothesis that an individual's risk or resilience to neuroinflammatory disorders and poor cognitive aging may critically depend on their early life experience, which can change immune reactivity within the brain for the remainder of the lifespan. For instance, early-life infection in rats can profoundly disrupt memory function in young adulthood, as well as accelerate age-related cognitive decline, both of which are linked to enduring changes in glial function that occur in response to the initial infection. We discuss these findings within the context of the growing literature on the role of immune molecules and neuroimmune crosstalk in normal brain development. We highlight the intrinsic factors (e.g., chemokines, hormones) that regulate microglial development and their colonization of the embryonic and postnatal brain, and the capacity for disruption or "re-programming" of this crucial process by external events (e.g., stress, infection). An impact on glia, which in turn alters neural development, has the capacity to profoundly impact cognitive and mental health function at all stages of life.

Episodic and Semantic Autobiographical Memory and Everyday Memory during Late Childhood and Early Adolescence

Few studies have examined both episodic and semantic autobiographical memory (AM) performance during late childhood and early adolescence. Using the newly developed Children’s Autobiographical Interview (CAI), the present study examined the effects of age and sex on episodic and semantic AM and everyday memory in 182 children and adolescents. Results indicated that episodic and semantic AM both improved between 8 and 16 years of age; however, age-related changes were larger for episodic AM than for semantic AM. In addition, females were found to recall more episodic AM details, but not more semantic AM details, than males. Importantly, this sex difference in episodic AM recall was attenuated under conditions of high retrieval support (i.e., the use of probing questions). The ability to clearly visualize past events at the time of recollection was related to children’s episodic AM recall performance, particularly the retrieval of perceptual details. Finally, similar age and sex effects were found between episodic AM and everyday memory ability (e.g., memory for everyday activities). More specifically, older participants and females exhibited better episodic AM and everyday memory performance than younger participants and males. Overall, the present study provides important new insight into both episodic and semantic AM performance, as well as the relation between episodic AM and everyday memory, during late childhood and adolescence.

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.

Training with differential outcomes enhances discriminative learning and visuospatial recognition memory in children born prematurely

Previous studies have demonstrated that discriminative learning is facilitated when a particular outcome is associated with each relation to be learned. When this training procedure is applied (the differential outcome procedure; DOP), learning is faster and more accurate than when the more common non-differential outcome procedure is used. This enhancement of accuracy and acquisition has been called the differential outcome effect (DOE). Our primary purpose in the present study was to explore the DOE in children born with great prematurity performing a discriminative learning task (Experiment 1) or a delayed visuospatial recognition task (Experiment 2). In Experiment 1, participants showed a faster learning and a better performance when differential outcomes were used. In Experiment 2, a significant DOE was also observed. That is, premature children performed the visuospatial recognition task better when they received differential outcomes following their correct responses. By contrast, the overall performance of full-term children was similar in both differential and non-differential conditions. These results are first to show that the DOP can enhance learning of conditional discriminations and recognition memory in children born prematurely with very low birth-weight.

Plasticity of gray matter volume: the cellular and synaptic plasticity that underlies volumetric change

Fifty years ago, Mark Rosenzweig and coworkers described environmental effects on brain chemistry and gross brain weight. William Greenough then used stereological tools, electron microscopy, and the Golgi stain to demonstrate that enrichment led to dendritic growth and synapse addition. Together these forms of plasticity accounted for cortical expansion and a reduction in cell density. In parallel with other investigators, Greenough demonstrated that these effects were not limited to the rodent, the cortex, or development, but instead generalize to many species, brain regions, and life stages. Studies of the anatomical effects of enrichment foreshadowed the recent empirical evidence for cortical volumetric increases after environmental experience and training in humans. Since research in humans is limited to regional effects, the analysis of the cellular and synaptic effects of enrichment, and their contribution to volumetric increases can inform us of the potential cellular and subcellular plasticity the leads to volume change in humans.

Diffuse periventricular leukomalacia in preterm children: assessment of grey matter changes by MRI

BACKGROUND

Preterm children may have cognitive deficits and behavioural disorders suggestive of grey matter (GM) injury. The prevalence is higher in preterm children with diffuse periventricular leukomalacia (dPVL).

OBJECTIVE

Evaluate changes in the volume of 116 GM areas in preterm children with dPVL.

METHODS AND MATERIALS

Eleven preterm children with dPVL, gestational age 32.8 ± 2.6 weeks, examined at corrected age 22.0 ± 18.2 months and 33 matched preterm controls with normal brain MRI were studied. Volumes of 116 individual GM areas, and white matter/cerebrospinal fluid (WM/CSF) ratio were calculated on T1-weighted high-resolution images after segmentation.

RESULTS

Relative to controls, children with dPVL had decreased GM volume of the hippocampus, amygdala, and frontal lobes and temporal middle gyrus (P < 0.05); increased GM volume of the putamen, thalamus, globus pallidum, superior temporal gyrus and of the parietal and occipital lobes (P < 0.05) and lower WM volume/higher CSF volume (P < 0.05). WM/CSF ratios also differed (P < 0.05).

CONCLUSIONS

Preterm children with dPVL have increased regional GM volume in some areas probably related with a process of brain plasticity-regeneration and reduced GM volume in areas associated with cognition and memory.

Postnatal corticosteroids for prevention and treatment of chronic lung disease in the preterm newborn

Despite significant progress in the treatment of preterm neonates, bronchopulmonary dysplasia (BPD) continues to be a major cause of neonatal morbidity. Affected infants suffered from long-term pulmonary and nonpulmonary sequel. The pulmonary sequels include reactive airway disease and asthma during childhood and adolescence. Nonpulmonary sequels include poor coordination and muscle tone, difficulty in walking, vision and hearing problems, delayed cognitive development, and poor academic achievement. As inflammation seems to be a primary mediator of injury in pathogenesis of BPD, role of steroids as antiinflammatory agent has been extensively studied and proven to be efficacious in management. However, evidence is insufficient to make a recommendation regarding other glucocorticoid doses and preparations. Numerous studies have been performed to investigate the effects of steroid. The purpose of this paper is to evaluate these studies in order to elucidate the beneficial and harmful effects of steroid on the prevention and treatment of BPD.

Selective deficit in spatial location memory in extremely low birth weight children at age six: the PETIT study

Spatial location memory has rarely been assessed in young children due to a scarcity of developmentally appropriate tests. This study sought to compare nonverbal learning and recall in children born extremely low birth weight (ELBW; <1000 g) and less than 33 gestational weeks (GW) with term-born children at early school age using a recently developed and adapted test. We administered a modification of the Hopkins Board to 210 children at age six; 84 born ELBW (35 born < 26 GW; 49 born 26-33 GW) and 126 term-born. Six measures were obtained: naming, trials-to-criterion, errors-to-criterion, delayed item recall, delayed location recall, and percent retention. After age correction, ELBW children had worse general cognition, item naming, delayed item recall, delayed location recall, and percent retention than term-born children. Delayed item recall and percent retention performances of ELBW children remained worse after correction for general cognition. ELBW groups (< 26 GW and 26-33 GW) groups performed worse than term-born children in naming and delayed item recall with chronological age as covariate. Those born before 26 GW, but not 26-33 GW, performed worse than term-born children in delayed location recall and percent retention. Differences remained significant after controlling for gender, maternal education, and delivery type. All three groups' performance declined from final learning trial to delayed location recall, with a decline greater for less than 26 GW than term-born children. Extreme prematurity (< 26 GW) and ELBW are significant risk factors for spatial location memory deficit. The modified Hopkins Board discriminated high-risk preterm and term-born children at early school age and appears to be a useful test to measure this rarely studied cognitive capacity.

The biological basis of injury and neuroprotection in the fetal and neonatal brain

A compromised intrauterine environment that delivers low levels of oxygen and/or nutrients, or is infected or inflammatory, can result in fetal brain injury, abnormal brain development and in cases of chronic compromise, intrauterine growth restriction. Preterm birth can also be associated with injury to the developing brain and affect the normal trajectory of brain growth. This review will focus on the effects that episodes of perinatal hypoxia (acute, chronic, associated with inflammation or as an antecedent of preterm birth) can have on the developing brain. In animal models of these conditions we have found that relatively brief (acute) periods of fetal hypoxemia can have significant effects on the fetal brain, for example death of susceptible neuronal populations (cerebellum, hippocampus, cortex) and cerebral white matter damage. Chronic placental insufficiency which includes fetal hypoxemia, nutrient restriction and altered endocrine status can result in fetal growth restriction and long-term deficits in neural connectivity in addition to altered postnatal function, for example in the auditory and visual systems. Maternal/fetal inflammation can result in fetal brain damage, particularly but not exclusively in the white matter; injury is more pronounced when associated with fetal hypoxemia. In the baboon, in which the normal trajectory of growth is affected by preterm birth, there is a direct correlation between a higher flux in oxygen saturation and a greater extent of neuropathological damage. Currently, the only established therapy for neonatal encephalopathy in full term neonates is moderate hypothermia although this only offers some protection to moderately but not severely affected brains. There is no accepted therapy for injured preterm brains. Consequently the search for more efficacious treatments continues; we discuss neuroprotective agents (erythropoietin, N-acetyl cysteine, melatonin, creatine, neurosteroids) which we have trialed in appropriate animal models. The possibility of combining hypothermia with such agents or growth factors is now being considered. A deeper understanding of causal pathways in brain injury is essential for the development of efficacious strategies for neuroprotection.

Fetal and neonatal iron deficiency causes volume loss and alters the neurochemical profile of the adult rat hippocampus

OBJECTIVE

Perinatal iron deficiency results in persistent hippocampus-based cognitive deficits in adulthood despite iron supplementation. The objective of the present study was to determine the long-term effects of perinatal iron deficiency and its treatment on hippocampal anatomy and neurochemistry in formerly iron-deficient young adult rats.

METHODS

Perinatal iron deficiency was induced using a low-iron diet during gestation and the first postnatal week in male rats. Hippocampal size was determined using volumetric magnetic resonance imaging at 8 weeks of age. Hippocampal neurochemical profile, consisting of 17 metabolites indexing neuronal and glial integrity, energy reserves, amino acids, and myelination, was quantified using high-field in vivo (1)H NMR spectroscopy at 9.4T (N = 11) and compared with iron-sufficient control group (N = 10).

RESULTS

The brain iron concentration was 56% lower than the control group at 7 days of age in the iron-deficient group, but had recovered completely at 8 weeks. The cross-sectional area of the hippocampus was decreased by 12% in the formerly iron-deficient group (P = 0.0002). The hippocampal neurochemical profile was altered: relative to the control group, creatine, lactate, N-acetylaspartylglutamate, and taurine concentrations were 6-29% lower, and glutamine concentration 18% higher in the formerly iron-deficient hippocampus (P < 0.05).

DISCUSSION

Perinatal iron deficiency was associated with reduced hippocampal size and altered neurochemistry in adulthood, despite correction of brain iron deficiency. The neurochemical changes suggest suppressed energy metabolism, neuronal activity, and plasticity in the formerly iron-deficient hippocampus. These anatomic and neurochemical changes are consistent with previous structural and behavioral studies demonstrating long-term hippocampal dysfunction following perinatal iron deficiency.

Associations between regional brain volumes at term-equivalent age and development at 2 years of age in preterm children

BACKGROUND

Altered brain volumes and associations between volumes and developmental outcomes have been reported in prematurely born children.

OBJECTIVES

To assess which regional brain volumes are different in very low birth weight (VLBW) children without neurodevelopmental impairments ([NDI] cerebral palsy, hearing loss, blindness and significantly delayed cognitive performance) compared with VLBW children with NDI, and to evaluate the association between regional brain volumes at term-equivalent age and cognitive development and neurological performance at a corrected age of 2 years.

MATERIALS AND METHODS

The study group consisted of a regional cohort of 164 VLBW children, divided into one group of children without NDI (n = 148) and one group of children with NDI (n = 16). Brain (MRI) was performed at term-equivalent age, from which brain volumes were manually analysed. Cognitive development was assessed with the Bayley Scales of Infant Development II (BSID-II), and neurological performance with the Hammersmith Infant Neurological Examination at the corrected age of 2 years.

RESULTS

The volumes of total brain tissue, cerebrum, frontal lobes, basal ganglia and thalami, and cerebellum were significantly smaller, and the volume of the ventricles significantly larger, in the children with NDI than in those without NDI. Even in children without NDI, a smaller cerebellar volume was significantly correlated with poor neurological performance at 2 years of corrected age.

CONCLUSION

Volumetric analysis at brain MRI can provide an additional parameter for early prediction of outcome in VLBW children.

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.

Neonatal ultrasound results following very preterm birth predict adolescent behavioral and cognitive outcome

This study investigated the association between different neonatal ultrasonographic classifications and adolescent cognitive, educational, and behavioral outcomes following very preterm birth. Participants included a group of 120 adolescents who were born very preterm (<33 weeks of gestation), subdivided into three groups according to their neonatal cerebral ultrasound (US) classifications: (a) normal (N = 69), (b) periventricular hemorrhage (PVH, N = 37), and (c) PVH with ventricular dilatation (PVH + DIL, N = 14), and 50 controls. The cognitive functions assessed were full-scale IQ, phonological and semantic verbal fluency, and visual-motor integration. Educational outcomes included reading and spelling; behavioral outcomes were assessed with the Rutter Parents' Scale and the Premorbid Adjustment Scale (PAS). Adolescent outcome scores were compared among the four groups. A main effect for group was observed for full-scale IQ, Rutter Parents' Scale total scores, and PAS total scores, after controlling for gestational age, socioeconomic status and gender, with the PVH + DIL group showing the most impaired scores compared to the other groups. The current results demonstrate that routine neonatal ultrasound classifications are associated with later cognitive and behavioral outcome. Neonatal ultrasounds could aid in the identification of subgroups of children who are at increased risk of neurodevelopmental problems. These at risk subgroups could then be referred to appropriate early intervention services.

Fetal hippocampal development: analysis by magnetic resonance imaging volumetry

The hippocampal formation plays an important role in learning and memory; however, data on its development in utero in humans are limited. This study was performed to evaluate hippocampal development in healthy fetuses using 3D reconstructed MRI. A cohort of 20 healthy pregnant women underwent prenatal MRI at a median GA of 24.9 wk (range, 21.3-31.9 wk); six of the women also had a second fetal MRI performed at a 6-wk interval. Routine 2D ultrafast T2-weighted images were used to reconstruct a 3D volume image, which was then used to manually segment the right and left hippocampi. Total hippocampal volume was calculated for each subject and compared against GA. There was a linear increase in total hippocampal volume with increasing GA (p < 0.001). For subjects scanned twice, there was an increase in hippocampal size on the second fetal MRI (p = 0.0004). This represents the first volumetric study of fetal hippocampal development in vivo. This normative volumetric data will be helpful for future comparison studies of suspected developmental abnormalities of hippocampal structure and function.

Late preterm infants have worse 24-month neurodevelopmental outcomes than term infants

BACKGROUND

Late preterm infants (34-37 weeks' gestation) are often perceived at similar risks for morbidity and mortality as term infants.

OBJECTIVE

To compare the neurodevelopmental outcomes of late preterm to term infants.

METHODS

Our study sample of 6300 term and 1200 late preterm infants came from the Early Childhood Longitudinal Study-Birth Cohort. We used general estimating equations to get weighted odds of having developmental delay, mental index scores (MDI) or psychomotor index scores (PDI) < 70, at 24 months of age.

RESULTS

Late preterm infants compared with term infants had lower MDI (85 vs 89) and PDI (88 vs 92), both P < .0001, respectively. A higher proportion of late preterm infants compared with term infants had an MDI <70 (21% vs 16%; P < .0001). An equal number had PDIs <70 (6.1% vs 6.5%). After controlling for statistically significant and clinically relevant descriptive characteristics, late preterm infants still had higher odds of mental (odds ratio: 1.52 [95% confidence interval: 1.26-1.82] P < .0001) or physical (odds ratio: 1.56 [95% confidence interval: 1.30-1.89] P < .0001) developmental delay.

CONCLUSIONS

Late preterm infants have poorer neurodevelopmental outcomes than term infants and have increased odds to have a mental and/or physical developmental delay.

Implicit and explicit learning: applications from basic research to sports for individuals with impaired movement dynamics

PURPOSE

Motor skills can be learned in an explicit or an implicit manner. Explicit learning places high demands on working memory capacity, but engagement of working memory is largely circumvented when skills are learned implicitly. We propose that individuals with impaired movement dynamics may benefit from implicit learning methods when acquiring sports-related motor skills.

METHOD

We discuss converging evidence that individuals with cerebral palsy and children born prematurely have compromised working memory capacity. This may in part explain the difficulties they encounter when learning motor and other skills. We also review tentative evidence that older people, whose movement dynamics deteriorate, can implicitly learn sports-related motor skills and that this results in more durable performance gains than explicit learning.

RESULTS

Individuals with altered movement dynamics and compromised working memory can benefit from implicit motor learning.

CONCLUSION

We conclude with an appeal for more extensive evaluation of the merits of implicit motor learning in individuals with impaired movement dynamics.