Neural bases of behavior selection without an objective correct answer

Life choice (e.g. occupation choice) often includes situations with two or more possible answers. How does the brain respond to such conflict-ridden situations? We investigated whether the dorsal anterior cingulate cortex (dACC) evaluates the degree of conflict between possible answers. Additionally, we investigated whether the medial prefrontal cortex (MPFC) or the medial temporal lobe (MTL) has a function in behavior selection with plural possible answers. We used an occupational choice task (e.g. which occupation do you think you could do better?—dancer or chemist) with two possible answers and a word-length task (e.g. which word is longer?—dentist or comedian) that has a correct answer. The conflicts in each task were manipulated. Results showed that the dACC and the MTL were activated when the conflict during occupational choice was large, and that the MPFC and posterior cingulate cortex were activated more in the occupational choice task than in the word-length task. Our results show that the dACC evaluates the degree of conflict between possible answers, and that the MTL, MPFC, and posterior cingulate cortex have a function in behavior selection without an objective correct answer. It is thought that the MTL functions to reduce conflict when a large-conflict is detected in the dACC. Furthermore, the MPFC and posterior cingulate are thought to have a function of biasing any of the plural answers in behavior selection without an objective answer.