Brain morphological variability between whites and African Americans: the importance of racial identity in brain imaging research.

In a segregated society, marked by a historical background of inequalities, there is a consistent under-representation of ethnic and racial minorities in biomedical research, causing disparities in understanding genetic and acquired diseases as well as in the effectiveness of clinical treatments affecting different groups. The repeated inclusion of small and non-representative samples of the population in neuroimaging research has led to generalization bias in the morphological characterization of the human brain. A few brain morphometric studies between Whites and African Americans have reported differences in orbitofrontal volumetry and insula cortical thickness. Nevertheless, these studies are mostly conducted in small samples and populations with cognitive impairment. For this reason, this study aimed to identify brain morphological variability due to racial identity in representative samples. We hypothesized that, in neurotypical young adults, there are differences in brain morphometry between participants with distinct racial identities. We analyzed the Human Connectome Project (HCP) database to test this hypothesis. Brain volumetry, cortical thickness, and cortical surface area measures of participants identified as Whites (n = 338) or African Americans (n = 56) were analyzed. Non-parametrical permutation analysis of covariance between these racial identity groups adjusting for age, sex, education, and economic income was implemented. Results indicated volumetric differences in choroid plexus, supratentorial, white matter, and subcortical brain structures. Moreover, differences in cortical thickness and surface area in frontal, parietal, temporal, and occipital brain regions were identified between groups. In this regard, the inclusion of sub-representative minorities in neuroimaging research, such as African American persons, is fundamental for the comprehension of human brain morphometric diversity and to design personalized clinical brain treatments for this population.

Neuroimaging Association Scores: reliability and validity of aggregate measures of brain structural features linked to mental disorders in youth.

In genetics, aggregation of many loci with small effect sizes into a single score improved prediction. Nevertheless, studies applying easily replicable weighted scores to neuroimaging data are lacking. Our aim was to assess the reliability and validity of the Neuroimaging Association Score (NAS), which combines information from structural brain features previously linked to mental disorders. Participants were 726 youth (aged 6-14) from two cities in Brazil who underwent MRI and psychopathology assessment at baseline and 387 at 3-year follow-up. Results were replicated in two samples: IMAGEN (n = 1627) and the Healthy Brain Network (n = 843). NAS were derived by summing the product of each standardized brain feature by the effect size of the association of that brain feature with seven psychiatric disorders documented by previous meta-analyses. NAS were calculated for surface area, cortical thickness and subcortical volumes using T1-weighted scans. NAS reliability, temporal stability and psychopathology and cognition prediction were analyzed. NAS for surface area showed high internal consistency and 3-year stability and predicted general psychopathology and cognition with higher replicability than specific symptomatic domains for all samples. They also predicted general psychopathology with higher replicability than single structures alone, accounting for 1-3% of the variance, but without directionality. The NAS for cortical thickness and subcortical volumes showed lower internal consistency and less replicable associations with behavioural phenotypes. These findings indicate the NAS based on surface area might be replicable markers of general psychopathology, but these links are unlikely to be causal or clinically useful yet.

Cortical Morphometry is Associated with Neuropsychological Function in Healthy 8-Year-Old Children.

BACKGROUND AND PURPOSE: Cortical development is essential for children's neurocognition. In this study, we evaluated how variations in cortical morphometry in normal children are associated with outcome differences in multiple domains of cognition. METHODS: Eight-year-old children were recruited for a brain MRI followed by a battery of neuropsychological assessments. The MRI scan included 3D-T1-weighted imaging for cortical morphometry in 34 regions defined by the Desikan atlas. The neuropsychological assessments included the Reynolds Intellectual Assessment Scales (RIAS) for IQ, Clinical Evaluation of Language Fundamentals (CELF-4) for language, Children's Memory Scale (CMS) for memory, Wide Range Achievement Test (WRAT-4) for academic skills, and Behavior Rating Inventory of Executive Function (BRIEF) for executive functions. The relationships between MRI measured cortical features, including gray matter volume, surface area, and cortical thickness for different brain regions and neuropsychological test scores, were evaluated using partial correlation analyses controlled for age and sex. RESULTS: RIAS/CELF-4/CMS/WRAT-4/BRIEF scores showed significant correlations (R: [.38-.44], P: [.005-.046]) with gray matter volume, surface area, or cortical thickness in multiple brain regions. Gray matter volume in the medial orbitofrontal/ventromedial prefrontal cortex appeared to be a sensitive marker for overall neurocognition as it significantly correlated with IQ, language, memory, and executive function behaviors. The superior temporal gyrus and banks of superior temporal sulcus appeared to be most sensitive to reflect overall language function as their cortical features consistently correlated with language-related test scores. CONCLUSIONS: Cortical morphometry significantly correlated with neuropsychological function in healthy children; certain regions/features may serve as sensitive imaging markers.

Cortical folding is altered before surgery in infants with congenital heart disease.

Infants with congenital heart disease have altered brain development. We characterized cortical folding, a critical part of brain development, in congenital heart disease infants and demonstrated an overall decrease in cortical surface area and cortical folding with regional alterations in the right lateral sulcus and left orbitofrontal region, cingulate region, and central sulcus. These abnormalities were present prior to surgery.