Hippocampal and midbrain activation to different event types during learning. The relationship between (A) hippocampal and (B) midbrain activation during learning and generalization performance at test was strongest for the F2–S1 learning trials. Regression analyses (left) revealed that subsequent generalization correlated with learning-phase activation increases to F2–S1 trials in both bilateral hippocampus (data shown for right hippocampus) and midbrain (Ps<.05, corrected); no other correlations survived correction for multiple comparisons. Similarly, increased activation during learning of F2–S1 events showed the strongest difference across ‘good’ and ‘poor’ generalization subgroups. The ‘good’ (Ps<0.05), but not the ‘poor’ (Ps>0.40), generalization group demonstrated a significant increase in bilateral hippocampal and midbrain activation from early to late learning of F2–S1 trials. In the midbrain, this increase was selective to the F2–S1 trials, whereas in the hippocampus, a qualitatively similar effect was observed for the F1–S1 and F1–S2 trials (see Supplemental Results). Error bars +/− S.E.M.