The Neural System of Postdecision Evaluation in Rostral Frontal Cortex during Problem-solving Tasks

Little attention has been paid to the postdecision processing in fMRI studies with task paradigms in which there was no explicit feedback. Although late-onset BOLD responses were previously observed in the lateral frontopolar cortex after the familiar-novel decision on visually presented words, the nature of neural activations that caused the late-onset BOLD responses remained elusive. We here found, in human experts conducting complicated problem-solving tasks in their expertise domain, that the rostral frontal cortex, including the lateral frontopolar cortex, along with the anterior inferior parietal lobule, was activated only during the postdecision period, although there was no feedback. That is, these areas showed late-onset BOLD responses, and fitting of the BOLD responses with different models indicates that they were caused by neural activations that occurred after the decision. However, there was no response after performing a sensory-motor control task, and the magnitude of postdecision activations was correlated with the degree of uncertainty about the preceding decision, which suggests that the postdecision neural activations were associated with the preceding decision procedure. Furthermore, the same set of areas was more strongly activated when the subject explicitly rethought the preceding problem. These results suggest that the rostral frontal cortex, together with anterior inferior parietal lobule, comprises a network for uncertainty monitoring and exploration of alternative resolutions in postdecision evaluation. The present results thus introduce a new aspect of the functional gradient along the rostrocaudal axis in the frontal cortex.