Highlights d Medial prefrontal cortex (mPFC) persistently encodes valuebased decision variables d Relative value signals are stable, and total value signals decay d Persistent decision variables are weakly represented in premotor cortex d mPFC projections to dorsomedial striatum persistently represent decision variables

Serotonin neurons modulate learning rate through uncertainty Highlights d Mice demonstrate variable behavioral flexibility during decision making d Flexible behavior can be characterized as meta-learning guided by uncertainty d Serotonin neuron activity correlates with expected and unexpected uncertainty d Reversible inhibition of serotonin neuron activity impairs meta-learning

Parallel processing circuits are thought to dramatically expand the network capabilities of the nervous system. Magnocellular and parvocellular oxytocin neurons have been proposed to subserve two parallel streams of social information processing, which allow a single molecule to encode a diverse array of ethologically distinct behaviors, although to date direct evidence to support this hypothesis is lacking. Here we provide the first comprehensive characterization of magnocellular and parvocellular oxytocin neurons, validated across anatomical, projection target, electrophysiological, and transcriptional criteria. We next used novel multiple feature selection tools in Fmr1 KO mice to provide direct evidence that normal functioning of the parvocellular but not magnocellular oxytocin pathway is required for autism-relevant social reward behavior. Finally, we demonstrate that autism risk genes are uniquely enriched in parvocellular oxytocin neurons. Taken together these results provide the first evidence that oxytocin pathway specific pathogenic mechanisms account for social impairments across a broad range of autism etiologies.