Rule-dependent transformation of observed into self-actions in macaque ventral premotor cortex

The ventral premotor cortex (PMv) has been implicated in both action selection and the perception of observed actions, but it remains unclear whether PMv activity during action observation reflects the observed action itself, or variables related to the observers own action when the observed action becomes behaviourally relevant. Here, we recorded neural activity in macaque PMv during a task that dissociated observed action, rule context, and the subsequently selected self-action. Population activity during observation was already biased toward the upcoming self-action and became increasingly aligned with it. At the level of single neurons, subsets showed modulation by rule and required self-action beyond the observed action. Task-related variables coexisted during observation, rather than being organized into distinct sequential stages. These findings indicate that PMv activity during action observation is not solely determined by the observed action, but instead reflects variables related to the selection of the agents own action, consistent with a transformation from observed action to self-action.