2.6. Whole‐brain fixel‐based analysis

To perform FBA between different time points, general linear models were applied for each fixel as implemented in the most recent version of MRtrix3, which enables longitudinal FBA. In a paired t‐test design, repeated measures of fixel metrics were compared between T1 and T2, T1 and T3 as well as T1 and T4 separately for patients with left‐ and right hemispheric stroke. To allow for smoothing and a statistical inference informed by the template tractogram, connectivity‐based fixel enhancement was applied (Raffelt et al., 2015). Permutation‐based correction for family‐wise errors was performed on resulting p‐values using the recommended, FWE‐corrected threshold of p < .05 (Nichols & Holmes, 2002; Winkler, Ridgway, Webster, Smith, & Nichols, 2014).