White Matter Integrity and Volumetrics in the Investigation of Structural Connectivity in School-Aged High Functioning Boys with ASD

Background: Given the frequent replication in ASD research of the findings of large brains, increased white matter and of atypical connectivity, it is important to investigate the nature and distribution of the tissue changes that may be contributing to these observed abnormalities.
Objectives: Our goal is to investigate white matter structural integrity in a well-characterized cohort using MRI methods to quantitate water diffusion properties, and to assess the relationship of these findings to neurocognitive phenotypic features.

Methods: High resolution Diffusion MRI and 1mm isotropic T1-weighted MPRAGE scans were acquired using  a 3T Siemens scanner on high-functioning 6-13 year olds with Autism Spectrum Disorder and age matched typically developing children.
Analytical methods include Voxelwise statistical analysis performed using FSL’s Tract Based Spatial Statistics (TBSS) tool and volume-based analyses using Freesurfer and manual volumetric analysis using segmentation and parcellation techniques from the Center for Morphometric Analysis at MGH.  TBSS was used to localize areas where group differences in white matter Fractional Anisotropy and Mean Diffusivity show significant differences.  Volumetric methods were then used to further quantify characteristics of regions with altered white matter properties. 
Results: Preliminary results indicate some differences in the measured DTI metrics, which will be presented in relation to whole-brain volumetric and neurocognitive data.
Conclusions: The use of several coordinated macroanatomic methods to assess white matter alterations in ASD is important for sharpening hypotheses about underlying microanatomic alterations contributory to abnormal connectivity.