Dissociable substrates for body motion and physical experience in the human action observation network.

Observation of human actions recruits a well-defined network of brain regions, yet the purpose of this action observation network (AON) remains under debate. Some authors contend that this network has developed to respond specifically to observation of human actions. Conversely, others suggest that this network responds in a similar manner to actions prompted by human and non-human cues, and that one's familiarity with the action is the critical factor that drives this network. Previous studies investigating human and non-human action cues often confound novelty and stimulus form. Here, we used a dance-learning paradigm to assess AON activity during observation of trained and untrained dance cues where a human model was present or absent. Results show that individual components of the AON respond differently to the human form and to dance training. The bilateral superior temporal cortex responds preferentially to videos with a human present, regardless of training experience. Conversely, the right ventral premotor cortex responds more strongly when observing sequences that had been trained, regardless of the presence of a human. Our findings suggest that the AON comprises separate and dissociable components for motor planning and observing other people's actions.