Identifying interindividual variability of social perception and associated brain anatomical correlations in children with autism spectrum disorder using eye-tracking and diffusion tensor imaging MRI (DTI-MRI)

Even though deficits in social cognition constitute a core characteristic of autism spectrum disorders, a large heterogeneity exists regarding individual social performances and its neural basis remains poorly investigated. Here, we used eye-tracking to objectively measure interindividual variability in social perception and its correlation with white matter microstructure, measured with diffusion tensor imaging MRI, in 25 children with autism spectrum disorder (8.5 ± 3.8 years). Beyond confirming deficits in social perception in participants with autism spectrum disorder compared 24 typically developing controls (10.5 ± 2.9 years), results revealed a large interindividual variability of such behavior among individuals with autism spectrum disorder. Whole-brain analysis showed in both autism spectrum disorder and typically developing groups a positive correlation between number of fixations to the eyes and fractional anisotropy values mainly in right and left superior longitudinal tracts. In children with autism spectrum disorder a correlation was also observed in right and left inferior longitudinal tracts. Importantly, a significant interaction between group and number of fixations to the eyes was observed within the anterior portion of the right inferior longitudinal fasciculus, mainly in the right anterior temporal region. This additional correlation in a supplementary region suggests the existence of a compensatory brain mechanism, which may support enhanced performance in social perception among children with autism spectrum disorder.

Neuroimaging evidence of brain abnormalities in mastocytosis

Mastocytosis is a rare disease in which chronic symptoms are related to mast cell accumulation and activation. Patients can display depression-anxiety-like symptoms and cognitive impairment. The pathophysiology of these symptoms may be associated with tissular mast cell infiltration, mast cell mediator release or both. The objective of this study is to perform morphological or functional brain analyses in mastocytosis to identify brain changes associated with this mast cell disorder. We performed a prospective and monocentric comparative study to evaluate the link between subjective psycho-cognitive complaints, psychiatric evaluation and objective medical data using magnetic resonance imaging with morphological and perfusion sequences (arterial spin-labeled perfusion) in 39 patients with mastocytosis compared with 33 healthy controls. In the test cohort of 39 mastocytosis patients with psycho-cognitive complaints, we found that 49% of them had morphological brain abnormalities, mainly abnormal punctuated white matter abnormalities (WMA). WMA were equally frequent in cutaneous mastocytosis patients and indolent forms of systemic mastocytosis patients (42% and 41% of patients with WMA, respectively). Patients with WMA showed increased perfusion in the putamen compared with patients without WMA and with healthy controls. Putamen perfusion was also negatively correlated with depression subscores. This study demonstrates, for we believe the first time, a high prevalence of morphological and functional abnormalities in the brains of mastocytosis patients with neuropsychiatric complaints. Further studies are required to determine the mechanism underpinning this association and to ascertain its specificity.

Genomic architecture of human neuroanatomical diversity

Human brain anatomy is strikingly diverse and highly inheritable: genetic factors may explain up to 80% of its variability. Prior studies have tried to detect genetic variants with a large effect on neuroanatomical diversity, but those currently identified account for <5% of the variance. Here, based on our analyses of neuroimaging and whole-genome genotyping data from 1765 subjects, we show that up to 54% of this heritability is captured by large numbers of single-nucleotide polymorphisms of small-effect spread throughout the genome, especially within genes and close regulatory regions. The genetic bases of neuroanatomical diversity appear to be relatively independent of those of body size (height), but shared with those of verbal intelligence scores. The study of this genomic architecture should help us better understand brain evolution and disease.

The ENIGMA Consortium: large-scale collaborative analyses of neuroimaging and genetic data

The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Consortium is a collaborative network of researchers working together on a range of large-scale studies that integrate data from 70 institutions worldwide. Organized into Working Groups that tackle questions in neuroscience, genetics, and medicine, ENIGMA studies have analyzed neuroimaging data from over 12,826 subjects. In addition, data from 12,171 individuals were provided by the CHARGE consortium for replication of findings, in a total of 24,997 subjects. By meta-analyzing results from many sites, ENIGMA has detected factors that affect the brain that no individual site could detect on its own, and that require larger numbers of subjects than any individual neuroimaging study has currently collected. ENIGMA's first project was a genome-wide association study identifying common variants in the genome associated with hippocampal volume or intracranial volume. Continuing work is exploring genetic associations with subcortical volumes (ENIGMA2) and white matter microstructure (ENIGMA-DTI). Working groups also focus on understanding how schizophrenia, bipolar illness, major depression and attention deficit/hyperactivity disorder (ADHD) affect the brain. We review the current progress of the ENIGMA Consortium, along with challenges and unexpected discoveries made on the way.