Context-dependent effects of ketamine on emotional evidence integration

Understanding others' emotions requires continuously integrating noisy affective information as emotional states change over time. Research on emotion processing, however, has thus far focused on static environments or discrete events. Here, we developed a continuous emotional evidence integration task in which participants had to track the average emotional state in a rapidly changing sequence of faces under different levels of environmental volatility. This allowed us to examine emotion integration in changing environments. In online (n=92) and in-person (n=29) cohorts, participants integrated emotional information over longer timescales in stable environments while relying more strongly on recent evidence under volatility, consistent with principles established in perceptual decision-making. We further examined whether this process was modulated by ketamine, an NMDA receptor antagonist associated with evidence integration in the perceptual domain. We conducted a double-blind, placebo-controlled, within-subject study and probed emotion integration during the post-acute period, approximately 1.5 hours after the infusion. Ketamine modulated the temporal weighting of emotional evidence, shifting the balance between recent and past information depending on environmental volatility. Together, these findings show that emotional evidence integration dynamically adapts to the statistical structure of the environment and that ketamine can further modulate this process, which may have relevance for affective disorders.