Orbitofrontal cortex promotes trial-by-trial learning of risky, but not spatial, biases

Individual choices are not made in isolation but are embedded in a series of past experiences, decisions, and outcomes. The effects of past experiences on choices, often called sequential biases, are ubiquitous in perceptual and value-based decision-making, but their neural substrates are unclear. We trained rats to choose between explicitly cued guaranteed and probabilistic rewards in a task in which outcomes on each trial were independent. Behavioral variability often reflected the effects of previous trials, including increased willingness to take risks following risky wins, and spatial \"win-stay/lose-shift\" biases. Electrophysiological recordings from lateral orbitofrontal cortex (lOFC) revealed strong encoding of reward history and receipt, and optogenetic inhibition of lOFC during choice reporting eliminated rats increased preference for risk on subsequent trials following risky wins, but spared other sequential effects. Our data show that different sequential biases are neurally dissociable, and that the lOFCs role in adaptive behavior promotes learning of more abstract, task-specific biases (here, biases for the risky option), but not spatial ones. These data are consistent with proposals that the OFC represents the animals location in an abstract representation of task states, and highlight the lOFCs role in learning.