Memory deficits following neonatal critical illness: A common neurodevelopmental pathway

Summary Over the last decade, knowledge has emerged that children growing up after neonatal critical illness, irrespective of underlying diagnosis, are at risk of memory impairment and school problems. Strikingly, these problems are manifest even when intelligence is normal. In this review, we propose a common neurodevelopmental pathway following neonatal critical illness by demonstrating that the survivors of preterm birth, congenital heart disease, and severe respiratory failure, share an increased risk of long-term memory deficits and associated hippocampal alterations. Rather than being a consequence of underlying diagnosis, we suggest that this shared vulnerability is most likely related to common conditions associated with neonatal critical illness. These include hypoxia, neuroinflammation, stress, exposure to anaesthetics, or a complex interplay of these factors at different postconceptional ages. Future work should be aimed at improving early identification of patients at risk and evaluating intervention modalities, such as cognitive or exercise training

Functional Magnetic Resonance Imaging during Visual Perception Tasks in Adolescents Born Prematurely

Objectives: Impairments in visual perception are among the most common developmental difficulties related to being born prematurely, and they are often accompanied by problems in other developmental domains. Neural activation in participants born prematurely and full-term during tasks that assess several areas of visual perception has not been studied. To better understand the neural substrates of the visual perceptual impairments, we compared behavioral performance and brain activations during visual perception tasks in adolescents born very preterm (birth weight <= 1500 g or gestational age <32 weeks) and full-term. Methods: Tasks assessing visual closure, discrimination of a deviating figure, and discrimination of figure and ground from the Motor-Free Visual Perception Test, Third Edition were performed by participants born very preterm (n = 37) and full-term (n = 34) at 12 years of age during functional magnetic resonance imaging. Results: Behavioral performance in the visual perception tasks did not differ between the groups. However, during the visual closure task, brain activation was significantly stronger in the group born very preterm in a number of areas including the frontal, anterior cingulate, temporal, and posterior medial parietal/cingulate cortices, as well as in parts of the cerebellum, thalamus, and caudate nucleus. Conclusions: Differing activations during the visual closure task potentially reflect a compensatory neural process related to premature birth or lesser neural efficiency or may be a result of the use of compensatory behavioral strategies in the study group born very preterm.Peer reviewe

Reduced hippocampal subfield volumes and memory performance in preterm children with and without germinal matrix intraventricular hemorrhage.

Preterm newborns with germinal matrix-intraventricular hemorrhage (GM-IVH) are at a higher risk of evidencing neurodevelopmental alterations. Present study aimed to explore the long-term efects that GM-IVH have on hippocampal subfelds, and their correlates with memory. The sample consisted of 58 participants, including 36 preterm-born (16 with GM-IVH and 20 without neonatal brain injury), and 22 full-term children aged between 6 and 15 years old. All participants underwent a cognitive assessment and magnetic resonance imaging study. GM-IVH children evidenced lower scores in Full Intelligence Quotient and memory measures compared to their low-risk preterm and full-term peers. High-risk preterm children with GM-IVH evidenced signifcantly lower total hippocampal volumes bilaterally and hippocampal subfeld volumes compared to both low-risk preterm and full-term groups. Finally, signifcant positive correlations between memory and hippocampal subfeld volumes were only found in preterm participants together; memory and the right CA-feld correlation remained signifcant after Bonferroni correction was applied (p= .002). In conclusion, memory alterations and both global and regional volumetric reductions in the hippocampus were found to be specifcally related to a preterm sample with GM-IVH. Nevertheless, results also suggest that prematurity per se has a long-lasting impact on the association between the right CA-feld volume and memory during childhood

Toddlers later diagnosed with autism exhibit multiple structural abnormalities in temporal corpus callosum fibers

Interhemispheric functional connectivity abnormalities are often reported in autism and it is thus not surprising that structural defects of the corpus callosum (CC) are consistently found using both traditional MRI and DTI techniques. Past DTI studies however, have subdivided the CC into 2 or 3 segments without regard for where fibers may project to within the cortex, thus placing limitations on our ability to understand the nature, timing and neurobehavioral impact of early CC abnormalities in autism. Leveraging a unique cohort of 97 toddlers (68 autism; 29 typical) we utilized a novel technique that identified seven CC tracts according to their cortical projections. Results revealed that younger (<2.5 years old), but not older toddlers with autism exhibited abnormally low mean, radial, and axial diffusivity values in the CC tracts connecting the occipital lobes and the temporal lobes. Fractional anisotropy and the cross sectional area of the temporal CC tract were significantly larger in young toddlers with autism. These findings indicate that water diffusion is more restricted and unidirectional in the temporal CC tract of young toddlers who develop autism. Such results may be explained by a potential overabundance of small caliber axons generated by excessive prenatal neural proliferation as proposed by previous genetic, animal model, and postmortem studies of autism. Furthermore, early diffusion measures in the temporal CC tract of the young toddlers were correlated with outcome measures of autism severity at later ages. These findings regarding the potential nature, timing, and location of early CC abnormalities in autism add to accumulating evidence, which suggests that altered inter-hemispheric connectivity, particularly across the temporal lobes, is a hallmark of the disorder

Univariate and multivariate pattern analysis of preterm subjects: a multimodal neuroimaging study

Background: Widespread lasting functional connectivity (FC) and brain volume changes in cortices and subcortices after premature birth have been researched in recent studies. However, the relationship remains unclear between spontaneously slow blood oxygen dependent level (BOLD) fluctuations and gray matter volume (GMV) changes in specific brain areas, such as temporal insular cortices, and whether classification methods based on MRI could be successfully applied to the identification of preterm individuals. In this thesis I hypothesized that in prematurely born adults 1. Ongoing neural excitability and brain activity, as estimated by regional functional connectivity of resting state functional MRI (rs-fMRI) is accompanied with altered low-frequency fluctuations and neonatal complications; 2. Altered regional functional connectivity is connected with superimposed cerebral structural reductions; and 3. multivariate neuroanatomical and functional brain patterns could be treated as features to identify preterm subjects from term subjects individually. Methods: To investigate these hypotheses, the principal results of structural alterations were measured with voxel-based morphometry (VBM), while rs-fMRI outcomes were estimated with amplitude of low-frequency fluctuations (ALFF) in analysis with ninety-four very preterm/very low birth weight (VP/VLBW) and ninety-two full-term (FT) born young adults. Results: The results of the thesis support the hypotheses by showing that, in univariate results, first in VP/VLBW grownups, ALFF was decreased in the left lateral temporal cortices no matter with global signal regression, and this reduction was closely associated with neonatal complications and cognitive variables. Second overlapped brain regions were found between reduced ALFF and reduced brain volumes in the left temporal cortices, and positively associated with each other, demonstrating a potential relationship between VBM and ALFF in this brain area. In multimodal multivariate pattern recognition analysis (MVPA), the gray matter volume (GMV) classifier displayed a higher accuracy (80.7%) contrast with the ALFF classifier (77.4%). The late fusion of GMV and ALFF did not outperform single GMV modality classification by reaching 80.4% accuracy. Moderator analysis from both rs-fMRI and structural MRI (sMRI) uncovered that the neuro-prematurity performance was predominantly determined by neonatal complications. Conclusions: In conclusion, these outcomes exhibit the long term effects of premature labour on lateral temporal cortices, which changed in both ongoing BOLD fluctuations and decreased cerebral structural volumes. This thesis further provided evidence that multivariate pattern analysis such as support vector machine (SVM) may identify imaging-based biomarkers and reliably detect signatures of preterm birth

Univariate and multivariate pattern analysis of preterm subjects: a multimodal neuroimaging study

Background: Widespread lasting functional connectivity (FC) and brain volume changes in cortices and subcortices after premature birth have been researched in recent studies. However, the relationship remains unclear between spontaneously slow blood oxygen dependent level (BOLD) fluctuations and gray matter volume (GMV) changes in specific brain areas, such as temporal insular cortices, and whether classification methods based on MRI could be successfully applied to the identification of preterm individuals. In this thesis I hypothesized that in prematurely born adults 1. Ongoing neural excitability and brain activity, as estimated by regional functional connectivity of resting state functional MRI (rs-fMRI) is accompanied with altered low-frequency fluctuations and neonatal complications; 2. Altered regional functional connectivity is connected with superimposed cerebral structural reductions; and 3. multivariate neuroanatomical and functional brain patterns could be treated as features to identify preterm subjects from term subjects individually. Methods: To investigate these hypotheses, the principal results of structural alterations were measured with voxel-based morphometry (VBM), while rs-fMRI outcomes were estimated with amplitude of low-frequency fluctuations (ALFF) in analysis with ninety-four very preterm/very low birth weight (VP/VLBW) and ninety-two full-term (FT) born young adults. Results: The results of the thesis support the hypotheses by showing that, in univariate results, first in VP/VLBW grownups, ALFF was decreased in the left lateral temporal cortices no matter with global signal regression, and this reduction was closely associated with neonatal complications and cognitive variables. Second overlapped brain regions were found between reduced ALFF and reduced brain volumes in the left temporal cortices, and positively associated with each other, demonstrating a potential relationship between VBM and ALFF in this brain area. In multimodal multivariate pattern recognition analysis (MVPA), the gray matter volume (GMV) classifier displayed a higher accuracy (80.7%) contrast with the ALFF classifier (77.4%). The late fusion of GMV and ALFF did not outperform single GMV modality classification by reaching 80.4% accuracy. Moderator analysis from both rs-fMRI and structural MRI (sMRI) uncovered that the neuro-prematurity performance was predominantly determined by neonatal complications. Conclusions: In conclusion, these outcomes exhibit the long term effects of premature labour on lateral temporal cortices, which changed in both ongoing BOLD fluctuations and decreased cerebral structural volumes. This thesis further provided evidence that multivariate pattern analysis such as support vector machine (SVM) may identify imaging-based biomarkers and reliably detect signatures of preterm birth

La participation des pères d'enfants prématurés dans la Méthode Kangourou et leur compétence parentale ultérieure

Cette étude s’intéresse au lien entre la quantité (fréquence) de la méthode en kangourou (MK) chez les pères d’enfants prématurés en lien avec leur compétence parentale ultérieure perçue ou observée. Elle considère également la relation conjugale comme étant un aspect pouvant venir expliquer ou modérer les éléments quantitatifs de l’expérience en MK du père et les mesures de compétence parentale subséquentes. Au total, 42 pères ont tenu un registre de la prise en MK de leur bébé et rempli des questionnaires avant la première prise en MK, à la sortie de l’hôpital et à nouveau rempli des questionnaires et ont été observés avec leur enfant 3 mois après la sortie de l’hôpital. Un résultat majeur en ressort, soit que plus la fréquence de prise en MK est élevée par rapport à la mère (ratio père/mère), plus le père rapporte un sentiment d’auto-efficacité (SAE) élevé à la sortie de l’hôpital, mais aussi trois mois plus tard, et ce, même en contrôlant pour le niveau initial du SAE. De plus, l’absence de la mère lors d’une tâche d’interaction entre le père et son enfant à domicile est liée à des comportements paternels favorisant le développement cognitif de l’enfant. Somme toute, ces résultats soulignent l’importance d’être à l’écoute des pères et de les valider dans leur rôle en leur offrant un espace auprès des soins de l’enfant. La conjointe ainsi que le personnel hospitalier peuvent agir à titre de facilitant et les encourager à s’approprier le rôle qui leur est dû. Quelques pistes d’interventions sont proposées

The relevance of posterior thalamo-cortical connectivity for visual short-term memory capacity

Visual short-term memory (vSTM) capacity represents the maximum number of visual items that can be perceived and stored into vSTM. One way to measure it is by using simple psycho-physical experiments together with the theory of visual attention (TVA) computational framework in which visual processing is conceived as a race between objects to be consciously perceived and stored into vSTM. The neural theory of visual attention (NTVA), which gives an interpretation of the TVA at both the cellular and systemic level, suggests that recurrent loops between posterior thalamus and visual cortices are relevant for vSTM capacity. Nevertheless, no clear evidence for the role of posterior thalamus and its connection to visual cortices in vSTM capacity has been found thus far. This thesis investigated the role of posterior thalamo-cortical connectivity in vSTM capacity in healthy young individuals as well as in two populations that have shown to exhibit both vSTM capacity impairments and posterior cortical and subcortical white matter damages: healthy aging and premature birth. We found that vSTM capacity in healthy young adults was significantly associated with the tracts connecting posterior thalamus to occipital cortices and their microstructure. However, this association was modified in elderly individuals and in young adults born prematurely, in which the recruitment of additional, cortico-cortical, tracts, takes place. Together, these findings bring the first structural evidence for the NTVA model with respect to the relevance of posterior thalamo-cortical tracts for vSTM capacity and show how alterations of these tracts affect vSTM capacity

The relevance of posterior thalamo-cortical connectivity for visual short-term memory capacity

Visual short-term memory (vSTM) capacity represents the maximum number of visual items that can be perceived and stored into vSTM. One way to measure it is by using simple psycho-physical experiments together with the theory of visual attention (TVA) computational framework in which visual processing is conceived as a race between objects to be consciously perceived and stored into vSTM. The neural theory of visual attention (NTVA), which gives an interpretation of the TVA at both the cellular and systemic level, suggests that recurrent loops between posterior thalamus and visual cortices are relevant for vSTM capacity. Nevertheless, no clear evidence for the role of posterior thalamus and its connection to visual cortices in vSTM capacity has been found thus far. This thesis investigated the role of posterior thalamo-cortical connectivity in vSTM capacity in healthy young individuals as well as in two populations that have shown to exhibit both vSTM capacity impairments and posterior cortical and subcortical white matter damages: healthy aging and premature birth. We found that vSTM capacity in healthy young adults was significantly associated with the tracts connecting posterior thalamus to occipital cortices and their microstructure. However, this association was modified in elderly individuals and in young adults born prematurely, in which the recruitment of additional, cortico-cortical, tracts, takes place. Together, these findings bring the first structural evidence for the NTVA model with respect to the relevance of posterior thalamo-cortical tracts for vSTM capacity and show how alterations of these tracts affect vSTM capacity