Subgoal- and Goal-Related Prediction Errors in Medial Prefrontal Cortex
A longstanding view of the organization of human and animal behavior holds that behavior is hierarchically organized, meaning that it can be understood as directed towards achieving superordinate goals through subordinate goals, or subgoals. For example, the superordinate goal of making coffee can be broken down as accomplishing a series of subgoals, namely boiling water, grinding coffee, pouring cream, etc. Learning and behavioral adaptation depend on prediction-error signals, which have been observed in ventral striatum (VS) and medial prefrontal cortex (mPFC). In past work, we have shown that prediction error signals (PEs) can be linked not only to superordinate goals, but also to subgoals. Here we present two functional magnetic resonance imagining experiments that replicate and extend these findings. In the first experiment, we replicated the finding that mPFC signals subgoal-related PEs, independently of goal PEs. Together with our past work, this experiment reveals that BOLD responses to PEs in mPFC are unsigned. In the second experiment, we showed that when a task involves both goal and subgoal PEs, mPFC shows only goal-related PEs, suggesting that context or attention can strongly impact hierarchical PE coding. Furthermore, we observed a dissociation between the coding of PEs in mPFC and VS. These experiments suggest that the mPFC selectively attends to information at different levels of hierarchy depending on the task context.