Figure 3. Unthresholded patterns of SIIPS1 predictive weights for some regions-of-interest (ROIs).

The ROIs include the nucleus accumbens (NAc), hippocampus, amygdala, PHG and caudate. The unthresholded pattern map used to make predictions included both positive and negative weights in each region, suggesting more complex, fine-grained mapping between these regions and pain. (a) Serial coronal views of the predictive weights within the NAc, showing positive predictive weights in a shell-like region and negative weights in a core-like region, as identified in a previous fMRI-based parcellation study⁴⁴. Differential roles of the NAc shell (pro-pain) versus core (anti-pain) subdivisions have been shown in animal literature¹⁵,⁴⁶. (b) Serial coronal views of the hippocampus and amygdala ROIs. Positive weights are apparent in the superficial and central subdivisions in the amygdala (as defined by ref. 47), and negative weights is the laterobasal group. A recent meta-analysis found that the superficial sub-region is often reported in experimental pain studies⁵¹. In the hippocampus, positive weights were found in some areas covering cornu ammonis and dentate gyrus⁴⁷, and also near caudate tail. (c) Serial axial views of the PHG ROI show positive weights in the entorhinal cortex (as defined by ref. 47) and a peri-amydaloid areas, and negative weights in other parahippocampal areas. (d) three-dimensional surface map of the un-thresholded SIIPS1 pattern for the ROIs. The pattern showed differential roles of caudate tail (positive) versus head (largely negative, but mixed), as suggested in animal⁴⁹ and metaanalysis studies⁵⁰, which associate caudate tail with stable, learned stimulus value and sensorimotor functions, and caudate head with more flexible, context-dependent stimulus value.