Two networks involved in producing and realizing plans.

Planning is essential for normal daily activities. Although the dorsolateral prefrontal cortex (DLPFC) is thought to be crucially involved in planning, it remains to be understood whether this contribution is attributable to working memory requirements of the tasks and when it occurs, whether during initial planning or during subsequent plan execution. Here, we compared patterns of activation observed when participants planned and executed their plans to solve Tower of Hanoi problems to when they had to memorize and reproduce externally presented sequences of moves. The DLPFC was preferentially active during initial planning relative to both plan execution and initial memorization of sequences of moves. By contrast, plan execution relied on posterior temporal areas, inferior frontal regions and the dorsolateral premotor cortex. We attribute activation in DLPFC to generation and evaluation of abstract sequences of responses, and activation in the regions underlying plan execution to rehearsal of planned sequences of moves.