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Monday, December 17, 2012

Global Functional Connectivity Abnormalities in Children with Fetal Alcohol Spectrum Disorders

Previous studies, including those employing diffusion tensor imaging (DTI), have revealed significant disturbances in the white matter of individuals with fetal alcohol spectrum disorders (FASD). Both macrostructural and microstructural abnormalities have been observed across levels of FASD severity. Emerging evidence suggests that these white matter abnormalities are associated with functional deficits. This study used resting-state functional MRI (fMRI) to evaluate the status of network functional connectivity in children with FASD compared with control subjects.
Participants included 24 children with FASD, ages 10 to 17, and 31 matched controls. Neurocognitive tests were administered including Wechsler Intelligence Scales, California Verbal Learning Test (CVLT), and Behavior Rating Inventory of Executive Functioning. High-resolution anatomical MRI data and 6-minute resting-state fMRI data were collected. The resting-state fMRI data were subjected to a graph theory analysis, and 4 global measures of cortical network connectivity were computed: characteristic path length, mean clustering coefficient, local efficiency, and global efficiency.

Results revealed significantly altered network connectivity in those with FASD. The characteristic path length was 3.1% higher (p = 0.04, Cohen's d = 0.47), and global efficiency was 1.9% lower (p = 0.04, d = 0.63) in children with FASD compared with controls, suggesting decreased network capacity that may have implications for integrative cognitive functioning. Global efficiency was significantly positively correlated with cortical thickness in frontal (r = 0.38, p = 0.005), temporal (r = 0.28, p = 0.043), and parietal (r = 0.36, p = 0.008) regions. No relationship between facial dysmorphology and functional connectivity was observed. Exploratory correlations suggested that global efficiency and characteristic path length are associated with capacity for immediate verbal memory on the CVLT (r = 0.41, p = 0.05 and r = 0.41, p = 0.01, respectively) among those with FASD.
Resting-state functional connectivity measures provide new insight into the integrity of brain networks in clinical populations such as FASD. Results demonstrate that children with FASD have alterations in core components of network function and that these aspects of brain integrity are related to measures of structure and cognitive functioning.

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