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.

早产对幼儿期海马体发育的影响在很大程度上尚不明确。本研究的目的是：1）比较7岁时极早产儿（VPT）与足月儿（FT）海马体的形状，并确定海马体形状是否与极早产儿的记忆和学习障碍有关；2）比较极早产儿和足月儿从相当于足月到7岁时海马体形状和体积的变化，并确定海马体随时间的发育是否能预测极早产儿的记忆和学习障碍。对125名极早产儿和25名足月儿在相当于足月和7岁时都进行了T1和T2磁共振成像。在两个时间点手动分割海马体，并通过边界点分布模型描述其形状。在7岁时测量记忆和学习结果。7岁时，极早产儿组的海马体折叠程度低于足月儿组。与足月儿组相比，极早产儿从婴儿期到7岁期间海马体的生长较少，但两组之间形状的变化相似。几乎没有证据表明海马体发育的测量指标与极早产儿组的记忆和学习障碍有关。这项研究表明，极早产儿的人海马体发育轨迹发生了改变，但这并不能预测记忆和学习障碍。需要进一步的研究来阐明极早产儿记忆和学习困难的机制。