Role of Central Serotonin in Anticipation of Rewarding and Punishing Outcomes: Effects of Selective Amygdala or Orbitofrontal 5-HT Depletion

Understanding the role of serotonin (or 5-hydroxytryptamine, 5-HT) in aversive processing has been hampered by the contradictory find-ings, across studies, of increased sensitivity to punishment in terms of subsequent response choice but decreased sensitivity to punish-ment-induced response suppression following gross depletion of central 5-HT. To address this apparent discrepancy, the present study determined whether both effects could be found in the same animals by performing localized 5-HT depletions in the amygdala or orbitofrontal cortex (OFC) of a New World monkey, the common mar-moset. 5-HT depletion in the amygdala impaired response choice on a probabilistic visual discrimination task by increasing the effective-ness of misleading, or false, punishment and reward, and decreased response suppression in a variable interval test of punishment sensi-tivity that employed the same reward and punisher. 5-HT depletion in the OFC also disrupted probabilistic discrimination learning and de