2.6.2. Correlations between white-matter tract count and behavior
To investigate the relation between learning and white-matter
tract count, we computed Spearman correlations between the
individual tract count in each voxel and RL accuracy for each seed
mask, age group, and condition (Fig. 2D). Again, only correlations
with p-value < 0.005 were considered significant (in line with de
Wit et al., 2012; van den Brink et al., 2014), and only clusters of at
least 50 voxels are reported. Note, however, that although tract
count correlated with behavior in these clusters these findings do
not necessarily indicate the terminal points of any tract. Rather, it
remains possible that these findings indicate differences within
tracts that traverse these areas. FAvalues were included as covariate
in all correlations to ensure that correlations were not biased by
local white-matter density. Because of a lack of systematic differences,
the final results are pooled over all 6 striatal seed regions.