Computational protocol: Worth the wait: effects of age of onset of marijuana use on white matter and impulsivity

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Protocol publication

[…] All processing of the diffusion-weighted images was performed using the FMRIB Software Library (version 4.1.9; http://www.fmrib.ox.ac.uk/fsl). Images were corrected for motion and eddy current to remove nonlinear artifacts and distortion from the datasets by applying affine alignment of each diffusion-weighted image to the first volume of the diffusion data without gradient (b = 0). A binary mask was generated from b = 0 image using the Brain Extraction Tool and tensors were fit using the b factor and diffusion direction matrix. Eigenvalues and eigenvectors were calculated for each voxel resulting in diffusion-weighted scalar maps, including whole brain FA and MD. These scalar maps were then aligned to standard space using the steps described for Tract-Based Spatial Statistics (TBSS), also part of the FSL package. Finally, FA and MD values were extracted in the anatomical regions defined by the John Hopkins University White Matter Label Atlas by registering the white matter labels to subject space using the inverse of the transform previously used to register subject data to standard space. In order to assess white matter differences in regions previously examined (Gruber et al. ), we limited our selection of atlas labels to the following bilateral brain regions: genu of the corpus callosum, corona radiata, and internal and external capsule. […]

Pipeline specifications

Software tools FSL, BET
Application Magnetic resonance imaging
Organisms Cannabis sativa