Departmental Colloquium by Peter Dayan (Max Planck for Biological Cybernetics)
Savouring and its Modulation by Prediction Errors
Humans and animals apparently extract intrinsic value from anticipating, or savoring, impending rewards. Further, when these outcomes are uncertain, people typically prefer to know their fate in advance. We link these two phenomena through the suggestion that reward prediction errors occasioned by the revelation can boost the level of savoring. The result is a behavioural anomaly that has consequences for maladaptivity such as gambling. We formalize this proposal, and investigate its neurobiology in humans using fMRI. In a task involving delayed probabilistic rewards, we found that participants had a greater preference for advance information for greater delays and lower probabilities, consistent with the boosting hypothesis. Ventromedial prefrontal cortex (vmPFC) encoded the time-varying anticipatory value signal predicted by the behavioral model. Reward prediction errors, encoded in dopaminergic midbrain, were coupled to vmPFC via hippocampus. We suggest that boosting might be driven by enhanced hippocampus-based imagination of future outcomes.
This is joint work with Kyo Iigaya, Tobias Hauser, Zeb Kurth-Nelson, John O'Doherty and Ray Dolan.