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Children born prematurely with very low birth weight (VLBW: bw  ≤ 1500 g) have an increased risk of preterm perinatal brain injury, which may subsequently alter the maturation of the brain, including the cerebral cortex. The aim of study was to assess cortical thickness and surface area in VLBW children compared with term-born controls, and to investigate possible relationships between cortical morphology and Full IQ. In this cross-sectional study, 37 VLBW and 104 term children born between the years 2003–2007 were assessed cognitively at 5–10 years of age, using age appropriate Wechsler tests. The FreeSurfer software was used to obtain estimates of cortical thickness and surface area based on T1-weighted MRI images at 1.5 Tesla. The VLBW children had smaller cortical surface area bilaterally in the frontal, temporal, and parietal lobes. A thicker cortex in the frontal and occipital regions and a thinner cortex in posterior parietal areas were observed in the VLBW group. There were significant differences in Full IQ between groups (VLBW M = 98, SD = 9.71; controls M = 108, SD = 13.57; p < 0.001). There was a positive relationship between IQ and surface area in both groups, albeit significant only in the larger control group. In the VLBW group, reduced IQ was associated with frontal cortical thickening and temporo-parietal thinning.We conclude that cortical deviations are evident in childhood even in VLBW children born in 2003–2007 who have received state of the art medical treatment in the perinatal period and who did not present with focal brain injuries on neonatal ultrasonography. The cortical deviations were associated with reduced cognitive functioning.

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Background The hippocampus, an essential structure for learning and memory, has a reduced volume in preterm born (gestational age < 37 weeks) individuals with very low birth weight (VLBW: birth weight < 1500 g), which may affect memory function. However, the hippocampus is a complex structure with distinct subfields related to specific memory functions. These subfields are differentially affected by a variety of neuropathological conditions, but it remains unclear how these subfields may be affected by medical complications following preterm birth which may cause aberrant brain development, and the consequences of this on learning and memory function in children with VLBW. Methods Children born preterm with VLBW ( n = 34) and term-born controls from the Norwegian Mother and Child Cohort Study (MoBa) ( n = 104) underwent structural MRI and a neuropsychological assessment of memory function at primary school age. FreeSurfer 6.0 was used to analyze the volumes of hippocampal subfields which were compared between groups, as was memory performance. Correlations between abnormal hippocampal subfields and memory performance were explored in the VLBW group. Results All absolute hippocampal subfield volumes were lower in the children with VLBW compared to MoBa term-born controls, and the volumes of the left and right dentate gyrus and the right subiculum remained significantly lower after correcting for total intracranial volume. The VLBW group had inferior working memory performance and the score on the subtest Spatial Span backwards was positively correlated to the volume of the right dentate gyrus. Conclusions Hippocampal subfield volumes seem to be differently affected by early brain development related to preterm birth. The dentate gyrus appears particularly susceptible to adverse effects of preterm birth. Reduced working memory function among children with VLBW was associated with smaller volume of right dentate gyrus. This finding demonstrates alterations in hippocampal structure-function relationships associated with early brain development related to preterm birth.

Background: Being born preterm with very low birth weight (VLBW) is related to aberrant brain development. Hippocampus is a brain region particularly vulnerable to injury, for instance from consequences following preterm birth. The hippocampus is a complex structure with distinct subfields related to specific memory functions which are differently affected by neuropathological conditions. The relationship between deviations in hippocampal subfields and memory function has not been studied in adults born preterm with VLBW previously. Aims:In this long-term follow-up study of a geographically based cohort (birth years 1986-88) of VLBW individuals and term born controls with normal birth weight, the main aim was to examine group differences in memory function and hippocampal volumes at age 26 years. We also explored hippocampal structurefunction relationships in the VLBW group.Methods: Fifty-two VLBW and 82 control individuals aged 26 years were examined clinically of whom 44 VLBW and 70 controls had high-quality structural cerebral MRI at 3T. The participants were assessed with subtests from Wechsler Memory Scale and Cambridge Neuropsychological Test Automated Battery on verbal, visual and working memory. From the T1 weighted 3D images, hippocampal subfield volumes were estimated in FreeSurfer 6.0. In addition to group comparisons, partial correlations were performed in the VLBW group between hippocampal subfields' volumes and neonatal risk factors, and between reduced hippocampal subfields' volumes and performance on the memory tests.Results: Adults with VLBW had lower verbal, visual and working memory scores compared with term born control adults. Absolute hippocampal total and most subfield volumes were smaller in the VLBW group than in the control group, but with different findings in men and women. When adjusting for intracranial volume, left and right cornu ammonis fields and left dentate gyrus were smaller in VLBW women, while the right subiculum was smaller in VLBW men compared with control women and men, respectively. There was a negative correlation between days on mechanical ventilation and volume of the left subiculum in the VLBW group. Smaller left dentate gyrus volume was associated with lower visual memory performance in the VLBW group. Conclusions:Adults born preterm with VLBW had lower performance on memory tests and smaller hippocampi compared with term born controls, and volume of dentate gyrus was associated with visual memory. Hippocampal subfield volumes seem to be differently affected following preterm birth in VLBW men and women.