Internal medicine

Pathology

Receptor

Placebo

Serotonin

Punishment (psychology)

Mood

Serotonergic

Psychiatry

Developmental psychology

Cognitive psychology

Psychology

Alternative medicine

Citalopram

Stimulus (psychology)

Medicine

Communications Biology

Instrumental learning is driven by a history of outcome success and failure. Here, we examined the impact of serotonin on learning from positive and negative outcomes. Healthy human volunteers were assessed twice, once after acute (single-dose), and once after prolonged (week-long) daily administration of the SSRI citalopram or placebo. Using computational modelling, we show that prolonged boosting of serotonin enhances learning from punishment and reduces learning from reward. This valence-dependent learning asymmetry increases subjects' tendency to avoid actions as a function of cumulative failure without leading to detrimental, or advantageous, outcomes. By contrast, no significant modulation of learning was observed following acute SSRI administration. However, differences between the effects of acute and prolonged administration were not significant. Overall, these findings may help explain how serotonergic agents impact on mood disorders.

Serotonin modulates asymmetric learning from reward and punishment in healthy human volunteers