TRACULA (TRActs Constrained by UnderLying Anatomy) is a tool for automatic reconstruction of a set of major white-matter pathways from diffusion-weighted MR images. It uses global probabilistic tractography with anatomical priors. Prior distributions on the neighboring anatomical structures of each pathway are derived from an atlas and combined with the FreeSurfer cortical parcellation and subcortical segmentation of the subject that is being analyzed to constrain the tractography solutions. This obviates the need for user interaction, e.g., to draw ROIs manually or to set thresholds on path angle and length, and thus automates the application of tractography to large datasets.


TRACULA in FreeSurfer 7.2:

TRACULA in FreeSurfer 6.0:

TRACULA in FreeSurfer 5.3:

TRACULA in FreeSurfer 5.2:

TRACULA in FreeSurfer 5.1:


All preprocessing of the diffusion-weighted images and reconstruction of the pathways is done by the trac-all script. Several options for this analysis stream can be set by the user in a configuration file (dmrirc file), which is passed as an argument to trac-all. For more information, see:

In summary the trac-all script can be used to:

Different command-line options allow the user to run all the above processing steps sequentially or only a single step.

The final output of TRACULA, the concatenation of the volumetric distributions of all reconstructed pathways, is a file called merged_*.mgz (the actual name depends on processing options). It can be visualized with freeview's -tv option, which displays the volumetric distributions of the pathways as isosurfaces like the ones shown in the image above.

A "robust max" thresholding is used within dmri_mergepaths and dmri_pathstats (i.e. the 99th percentile of the values in path.pd.nii.gz). This is to avoid cases where the absolute max is an outlier, which would cause the threshold to be too high and the isosurface in freeview to be generated from too few voxels.

Note that, because TRACULA relies on the underlying anatomy as derived from the FreeSurfer cortical parcellation and subcortical segmentation, these need to be generated before running trac-all. This means that before you run trac-all you will have to analyze your subjects' anatomical images with recon-all and make sure that they have a good-quality mri/aparc+aseg.mgz.


For step-by-step instructions on how to set up and run TRACULA, see the following tutorials from the FreeSurfer training workshop:

Related slide presentations from the workshop are available here:


If you use TRACULA, please cite:

If you use our measures of head motion, please cite:

If you use the longitudinal stream of TRACULA, please cite: