Figure 1.

Workflow for computing complex brain torque profiles. A: FSL preprocessing for normalizing the native brain volume to the standard MNI152 template using a 7 degrees of freedom (DOF) transformation. B: FreeSurfer processing on the spatially normalized brain volume to reconstruct cortical hemispheric surfaces. C: FreeSurfer surface-based interhemispheric registration to establish vertex-wise interhemispheric correspondence. D: Correcting for mis-registration of the brain mid-sagittal plane (MSP) by rotating the brain surface with an 3D angle between MSP and the plane x = 0. MSP was extracted as the plane best fitting the two hemispheric medial surfaces. E: FreeSurfer morphologic closing to fill sulci and smooth the cortical surface. F: Computing petalia and shift as the respective displacements of the left and right frontal/occipital extreme points along the antero-posterior and dorso-ventral axes respectively. Estimating bending as the angles between the planes best fitting the interhemispheric fissure in the frontal/occipital regions and MSP. G: Measuring left-right asymmetries in hemispheric width (Asym_width) and perimeter (Asym_perimeter) in 60 contiguous coronal brain slices. Sectional hemispheric width and perimeter was measured as the bounding box width and the average pial surface length at two ends of each brain slice respectively. H: Computing interhemispheric surface positional asymmetries along the left-right axis (Asym_LR) as vertex-wise differences in the distances to MSP on the x-axis, and asymmetries along the antero-posterior (Asym_AP) and dorsal-ventral axis (Asym_DV) as the vertex-wise relative displacements on the y- and z-axes respectively.