Our findings are consistent with behavioral studies showing decision-making deficits on the Iowa Gambling Task (IGT) in patients with ventral medial OFC lesions (16). Like patients with ventral medial frontal lesions, SDI are impaired on the IGT (27,28,29,30), although the impairments are less severe (30,28,31). This is consistent with our data suggesting that controls avoid “bad” decks over time more than SDI, but the differences were not significant. The negative correlation between medial OFC GM volume and decision to avoid bad cards is consistent with a role of OFC in evaluating expected outcomes. The correlation seemed mainly driven by controls, not SDI. We subsequently analyzed whether OFC GM correlated with abstinence, as such a relationship could suggest that chronic drug exposure influenced the OFC GM finding. However, there was no relationship between abstinence and morphology. On the other hand, the lack of a relationship does not imply a pre-morbid deficit as a number of other factors including severity of drug dependence, number or type of substances, and environmental factors could contribute to the findings. The possibilities of a pre-morbid condition, post-drug effect, or a combination remain equally likely.
