Figure 7:

Case C: failure of the canonical HRF to capture BOLD responses resulting in an incorrect sign of effect estimation. The focal effect is the group HRF difference in the incongruent condition. The voxel at the cross-hair (X, Y, Z) = (−7, −52, 18) is located in the right medial frontal gyrus. Each vertical bar or shaded band indicates one standard error. The estimated HRFs had a small to negligible overshoot with a relatively large undershoot, which is dramatically different from the assumed HRF. Thus, the canonical approach failed to accurately capture the group difference in peak height. In comparison, morphological characterization through HRF estimation provided strong statistical evidence for the presence of a group difference. The other two HRFs (BP con, and HV con) and neighboring voxels shared a similar HRF pattern (not shown here).