Sensitivity to reward and punishment and the prefrontal cortex in major depression.

Background: Patients with major depressive disorder (MDD) show neuropsychological impairments, including deficient executive functions and altered sensitivity to reward and punishment.

Methods: Executive functions (Wisconsin Card Sorting Test, WCST) and contingency learning based on the cumulative effect of reward and punishment (Iowa Gambling Test, IGT) were assessed in 30 medicated patients with unipolar MDD and in 20 healthy control volunteers. In the classic ABCD version of the IGT, advantageous decks are characterized by immediate small reward but even smaller future punishment. In the modified EFGH version, advantageous decks are characterized by immediate large punishment but even larger future reward.

Results: Patients with MDD were impaired in the WCST and in the ABCD version of the IGT but showed normal performances on the EFGH task. Depression, but not executive dysfunctions, significantly predicted performances on the EFGH task: less severe depressive symptoms were associated with better performances on the EFGH task.

Limitations: The sample size was small and only few neuropsychological tests were used. Unmedicated patients were not assessed. Individual personality style, response strategies, and behavioral impulsivity were not investigated.

Conclusions: Medicated patients with MDD show altered sensitivity to reward and punishment: immediate large reward enhanced related response patterns even when the strategy was disadvantageous and immediate large punishment did not prohibit related response patterns. Impairments in emotional decision-making were not a pure consequence of executive dysfunctions.