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Fronto-striatal connectivity predicts patience
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diffusivity (MD), measuring the amount of diffusion (Basser and Pierpaoli, 1996). White matter pathways were reconstructed using deterministic streamline tractography, based on the Fiber Assignment by Continuous Tracking (FACT) algorithm (Mori et al., 1999). Within each voxel of the cerebral white matter, 8 streamlines were started, following the computed diffusion directions from voxel to voxel until one of the stopping criteria was reached (being FA<0.1, sharp turn of 45 degrees or more, or exceeding brain tissue). This procedure resulted in a collection of reconstructable white matter tracts, from which fiber tracts of interest could be selected.
Figure 1. The frontostriatal WM tract within an individual subject is displayed in yellow, with the striatum and PFC as inclusion ROIs. Red regions display the VOI. The VOI was created across the whole sample; a voxel was included when it had a frontostriatal fiber running through in at least 50% of the total sample.
Frontostriatal volume of interest
We used a ‘volume of interest’ (VOI) to measure fronto-striatal white matter tracts as described by Peper et al. (2013). The VOI requires that the fiber tracts that are reconstructed for each subject in native space, are put into model space in order to create the VOI (for a detailed description, see Peper et al. (2013)). In short, tracts were required to run through both the striatum and PFC to be included as fronto-striatal white matter. Inclusion regions-of-interest (ROIs) were based on the automatic anatomical labeling (AAL) template (Tzourio-Mazoyer et al., 2002), including the caudate, putamen, and pallidum (AAL regions 71–76), as well as the dorsolateral, ventrolateral, and ventromedial prefrontal cortices (AAL regions 5– 10; 13– 16; 25–28). The ROIs were dilated with 2 voxels in all directions to ensure that they penetrate the white matter. Exclusion ROIs were the genu of the corpus
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