The files include feature spaces derived from voxel-wise gray matter volumes from the IXI dataset (https://brain-development.org/ixi-dataset/). T1-weighted images were preprocessed using Computational Anatomy Toolbox (CAT) version 12.8 (https://neuro-jena.github.io/cat/) and normalized gray matter segments (linear and non-linearly modulated) were used to calculate features. First, a whole-brain mask was used to select 238,955 voxels. Then, smoothing (S) with either 4 or 8 mm FWHM Gaussian kernel and resampling (R) using linear interpolation to 4 or 8 mm spatial resolution was applied (S4_R4: 29,852 features and S4_R8: 3747 features). IXI data is made available under the Creative Commons CC BY-SA 4.0 International license. If you use these features/data please acknowledge the source of the IXI data i.e., https://brain-development.org/ixi-dataset/.