Dissociable neural systems support retrieval of how and why action knowledge.

In everyday discourse, people typically represent actions in one of two ways: how they are performed or why they are performed. In the present study, we determined the neural systems that support these natural modes of representing actions. Participants underwent functional magnetic resonance imaging while identifying how and why people perform various familiar actions. Identifying how actions are performed produced activity in premotor areas that support the execution of actions and in higher-order visual areas that support the perception of action-related objects; this finding supports an embodied view of action knowledge. However, identifying why actions are performed preferentially engaged areas of the brain associated with representing and reasoning about mental states; these areas were right temporoparietal junction, precuneus, dorsomedial prefrontal cortex, and posterior superior temporal sulcus. Our results suggest that why action knowledge is not sufficiently constituted by information in motor and visual systems, but requires a system for representing states of mind, which do not have reliable motor correlates or visual appearance.