Hippocampal and midbrain activation during learning predicts correct responding on the generalization trials at test. (A) Map-wise regression analyses revealed that the change in activation from early to late learning in left hippocampus (−28,−9,−17; 27 voxels), right hippocampus (31,−5,−20; 22 voxels), and a bilateral midbrain complex (3,−18,−12; 50 voxels) correlated with % correct generalization performance at test (P<0.001, extent threshold 5 voxels; P<0.05, small volume corrected for the hippocampus and midbrain). (B) BOLD % signal change data extracted from these hippocampal and midbrain regions (inclusive of all above-threshold voxels within a 6-mm sphere surrounding the peak voxel) confirmed the strong correlation between learning-phase activation increases and generalization performance. (C) When participants were median split based on generalization performance at test, an increase in hippocampal and midbrain activation from early to late learning was observed in participants who generalized well (‘good’ group), but not in participants who generalized poorly (‘poor’ group). Error bars +/− S.E.M.