Longitudinal analysis of brain network reorganization in preterm IUGR children at 1, 6 and 9 years-old

Intrauterine Growth Restriction (IUGR) due to placental insufficiency affects 5-10% of all pregnancies and it is associated with a wide range of short and long-term neurodevelopmental disorders. Different approaches have been considered to understand IUGR effects on brain development. Recently, connectomics has been used to analyze brain reorganization in IUGR children at one and six years of age. Connectomics estimates the brain network and describes it by different graph measures. Diffusion tensor imaging (DTI) can be used to infer the connectivity between regions, since it allows in-vivo estimation of fiber tracts inside the brain. In this study, DTI based connectomics was used to describe short- and long-term brain reorganization in IUGR. The connectome of a cohort of preterm IUGR and control children at 1, 6 and 9 years of age was estimated and analyzed to evaluate differences in the architecture of neural circuitry and its evolution during development.

Structural connectomics in brain diseases

Philipp Baumann, Alessandra Griffa, Patric Hagmann, Jean-Philippe Thiran

Imaging the connectome in vivo has become feasible through the integration of several rapidly developing fields of science and engineering, namely magnetic resonance imaging and in particular diffusion MRI on one side, image processing and network theory on the other side. This framework brings in vivo brain imaging closer to the real topology of the brain, contributing to narrow the existing gap between our understanding of brain structural organization on one side and of human behavior and cognition on the other side. Given the seminal technical progresses achieved in the last few years, it may be ready to tackle even greater challenges, namely exploring disease mechanisms. In this review we analyze the current situation from the technical and biological perspectives. First, we critically review the technical solutions proposed in the literature to perform clinical studies. We analyze for each step (i.e. MRI acquisition, network building and network statistical analysis) the advantages and potential limitations. In the second part we review the current literature available on a selected subset of diseases, namely, dementia, schizophrenia, multiple sclerosis and others, and try to extract for each disease the common findings and main differences between reports.

Elsevier2013

Neural substrates of psychosis revealed by altered dependencies between brain activity and white-matter architecture in individuals with 22q11 deletion syndrome

Karin Bortolin, Farnaz Delavari, Emeline Mullier, Maria Giulia Preti, Dimitri Nestor Alice Van De Ville

Background: Dysconnectivity has been consistently proposed as a major key mechanism in psychosis. Indeed, disruptions in large-scale structural and functional brain networks have been associated with psychotic symptoms. However, brain activity is largely constrained by underlying white matter pathways and the study of function-structure dependency, compared to conventional unimodal analysis, allows a biologically relevant assessment of neural mechanisms. The 22q11.2 deletion syndrome (22q11DS) constitutes a remarkable opportunity to study the pathophysiological processes of psychosis. Methods: 58 healthy controls and 57 deletion carriers, aged from 16 to 32 years old, underwent resting-state functional and diffusion-weighted magnetic resonance imaging. Deletion carriers were additionally fully assessed for psychotic symptoms. Firstly, we used a graph signal processing method to combine brain activity and structural connectivity measures to obtain regional structural decoupling indexes (SDIs). We use SDI to assess the differences of functional structural dependency (FSD) across the groups. Subsequently we investigated how alterations in FSDs are associated with the severity of positive psychotic symptoms in participants with 22q11DS. Results: In line with previous findings, participants in both groups showed a spatial gradient of FSD ranging from sensory-motor regions (stronger FSD) to regions involved in higher-order function (weaker FSD). Compared to controls, in participants with 22q11DS, and further in deletion carriers with more severe positive psychotic symptoms, the functional activity was more strongly dependent on the structure in parahippocampal gyrus and subcortical dopaminergic regions, while it was less dependent within the cingulate cortex. This analysis revealed group differences not otherwise detected when assessing the structural and functional nodal measures separately. Conclusions: Our findings point toward a disrupted modulation of functional activity on the underlying structure, which was further associated to psychopathology for candidate critical regions in 22q11DS. This study provides the first evidence for the clinical relevance of function-structure dependency and its contribution to the emergence of psychosis.

ELSEVIER SCI LTD2022

Neural substrates of psychosis revealed by altered dependencies between brain activity and white-matter architecture in individuals with 22q11 deletion syndrome

Karin Bortolin, Farnaz Delavari, Emeline Mullier, Maria Giulia Preti, Dimitri Nestor Alice Van De Ville

ELSEVIER SCI LTD2022