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.

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 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.

Motor imagery skills of children with Attention Deficit Hyperactivity Disorder and Developmental Coordination Disorder.

Up to 50% of children with ADHD experience motor impairment consistent with DCD. Debate continues as to whether this impairment is linked to inattention or is a genuine motor deficit. This study aimed to determine whether (1) inattention was greater in ADHD+DCD than in ADHD alone and (2) motor imagery deficits observed in DCD were present in ADHD+DCD. Four groups aged 7-12 years-ADHD, combined type, with motor impairment (ADHD+DCD; N=16) and alone (ADHD; N=14), DCD (N=10) and typically developing comparison children (N=18) participated. Levels of inattention did not differ between ADHD groups. On an imagined pointing task, children with DCD did not conform to speed accuracy trade-offs during imagined movements, but all other groups did. However, on a hand rotation task, both the ADHD+DCD and DCD groups were less accurate than the non-motor impaired groups, a finding not explained by differences in IQ, age, or working memory capacity. Overall, there was evidence that children with ADHD+DCD experience genuine motor control impairments indicating the impact of motor impairment in ADHD and its causal risk factors require more study. Motor impairment in ADHD should not be dismissed as a by-product of inattention.