16 September 2020: What is the contribution of human orbitofrontal cortex to decision making?

Thorsten Kahnt
Department of Neurology
Northwestern University Feinberg School of Medicine

Research across species has shown that the orbitofrontal cortex (OFC) is important for decision making. However, it is less clear what specific computations are carried out in this region that make it so important for this function. Recent work from our lab and others has shown that OFC activity is correlated with expectations about specific outcomes. In this talk, I will present evidence from functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) experiments suggesting that outcome expectations in OFC are required for decisions that are based on inferred or simulated outcomes, as opposed to behavior that can be based on direct experience alone. Because OFC is not directly accessible to TMS, we utilize network-targeted TMS and apply continuous theta burst stimulation (cTBS) to sites in lateral PFC that are individually selected to be functionally connected to the OFC. We show that OFC network-targeted cTBS selectively disrupts choices that require subjects to infer outcomes, without affecting choices that can be based on direct experiences alone. These findings suggest that the OFC contributes to decision making by representing associative relationships that can be used to simulate outcomes when direct experience is missing.