An action-observation network in the common marmoset identified by ultra-high field fMRI

The observation of others’ actions activates a network of temporal, parietal and premotor/prefrontal areas in macaque monkeys and humans. This action-observation network (AON) has been shown to play important roles in understanding the actions of others, learning by imitation, and social cognition in both species. It is unclear whether a similar network exists in New World primates, which separated from Old Word Primates ∼ 35 million years ago. Here we used ultra-high field fMRI at 9.4T in awake common marmosets ( Callithrix jacchus ) while they watched videos depicting the upper-limb of conspecifics performing goal-directed (grasping food) or non-goal-directed actions. We found that the observation of goal-directed actions, compared to non-goal directed ones, activated a temporo-parieto-frontal network, including areas 6 and 45 in premotor and prefrontal cortices, areas PGa-IPa, FST and the TE complex in occipito-temporal region and areas V6A, MIP, LIP and PG in the occipito-parietal cortex. These results show remarkable overlap with the AON observed in humans and macaques. These results demonstrate the existence of an evolutionarily conserved AON that likely predates the separation of Old and New World primates.