151. Salience and Default Mode Network Coupling Role in Expectancy-Mood Interactions in Depression

Reinforcement learning (RL) models of antidepressant placebo effects suggest that expectancies –encoded in the salience network (SN)– trigger mood changes that are perceived as reward signals. Yet, the mechanisms underlying these expectancy-mood interactions are still unknown. We hypothesized that greater SN-default mode network (DMN) coupling facilitates the shift from greater salience attribution to contextual cues (e.g., placebo) to context-dependent mood regulation in the DMN. To test this hypothesis, we examined SN-DMN functional connectivity as a moderator between antidepressant expectancies and placebo-induced mood improvement both acutely and over time.