Independent samples t-tests, corrected with intensity and cluster-based thresholding, revealed 10 clusters (≥ 54 μl) in which MJ+ALC teens showed significantly lower FA than controls (see Table 2). The most prominent areas of diminished FA were in the left SLF, left postcentral sensory gyrus, and bilateral crus cerebri (P<0.001, see Figure 1). Temporal regions including the right superior temporal gyrus (P<0.001), projection fibers of the left temporo-thalamic tract (P<0.01), and right inferior longitudinal fasciculus (P<0.01) showed FA diminutions in MJ+ALC users, as did association fibers in right inferior frontal (P<0.001), left occipital-frontal (P<0.01), and splenium (P<0.01) regions (p-values refer to difference in the average FA value within each cluster). Interestingly, in three right hemisphere clusters, MJ+ALC users had higher FA than controls (P<0.001): the cuneus region of the occipital lobe, anterior limb of the internal capsule, and arcuate portion of the right SLF (see Table 2).
