What is the role of orbitofrontal cortex in dopamine dependent reinforcement learning ? !

Orbitofrontal cortex (OFC) has been implicated in signalling reward expectancies, but its exact role , and how this differs from that the role of ventral striatum (VS), is an open question. One idea is that VS is the seat of value learning in model-free, dopamine-dependent reinforcement learning, while OFC represents values in dopamine-independent model-based learning. However, recent results [1] show that unilateral OFC lesions significantly alter dopaminergic prediction error signalling, as recorded from single units in the VTA of rats performing a learning task (described in [2]).