Object presence modulates activity within the somatosensory component of the action observation network

In the present study, we used functional magnetic resonance imaging to investigate the influence that the presence of an object, intended as the target for an action, might have on the neural circuit underlying the observation of the movement of others (action observation network [AON]). This system entails a simulation process of the observed movement occurring via the recruitment of the motor and somatosensory cortices involved in the execution of such movement. Here, participants were requested to observe grasping actions ending behind a partition knowing in advance whether a target-object would be present (i.e., object-directed action) or absent (i.e., non object-directed action). These “action” conditions were compared with “control” conditions in which a stationary hand was presented either alone or together with the target-object hidden behind the partition. Activation within most regions of the AON was similar for observing partially occluded object-related and non object-related actions. However, within one of the regions belonging to the AON, namely in the somatosensory cortices, blood oxygen level–dependent activity was modulated by the presence of a target-object. We interpreted such modulation as demonstration of the differential involvement of the somatosensory component of the AON for the coding of these 2 types of actions.