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

Abstract

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.

Alterations in development of hippocampal and cortical memory mechanisms following very preterm birth

“…Smaller bilateral hippocampal volume in VPT samples compared with controls has been described at school‐age (~9% volume reduction),12, 13 adolescence (~14% volume reduction),14, 15 and adulthood16, 17 although some studies have found no hippocampal volume differences when correcting for factors such as intracranial volume 18, 19. Interestingly, hippocampal volume at term, but not at 7 years of age (or the amount of growth between these time‐points), has been associated with episodic memory abilities at age seven 12, 18, 20. This suggests that children with early hippocampal damage may have a limited capacity for the development of episodic memory functions.…”

The predictive validity of neonatal MRI for neurodevelopmental outcome in very preterm children

“…While limited evidence is available to date, it is possible that certain dysmorphic features of important structures such as the hippocampus, cerebellum, and corpus callosum may assist is predicting future maturation processes and later neurodevelopmental impairments. 48,51 Furthermore, directly related to tissue and regional volumes is cortical folding. Primary sulci form from 14 to 26 weeks GA, secondary sulci evolve between 30 and 35 weeks, and tertiary sulci from 36 weeks, and as such, a critical period for cortical gyration for VP infants occurs when they are critically ill and exposed to a range of potentially harmful agents and procedures.…”

Alteration of the brain methylation landscape following postnatal inflammatory injury in rat pups

“…The susceptibility of these regions to methylation changes was also seen in models of maternal separation and in prenatal alcohol exposure. The number of genes associated to each pathway is in parenthesis infants had impaired hippocampal and cortical growth seen 7 years later 69,70 and even signs of increasing atrophy over time. [63][64][65][66] One major group of pathways that emerged from our methylome analysis following neonatal inflammation-induced WMI was related to the axon.…”