Neurofunctional modulation of brain regions by the observation of pointing and grasping actions.

Previous neuroimaging research on healthy humans has provided evidence for a neural system underlying the observation of another person's hand actions. However, whether the neural processes involved in this capacity are activated by the observation of other transitive hand actions such as pointing remains unknown. Therefore, using functional magnetic resonance imaging we investigated the neural mechanisms underlying the observation of static images representing the hand of a human model pointing to an object (pointing condition), grasping an object (grasping condition), or resting in proximity of an object (control condition). The results indicated that activity within portions of the lateral occipitotemporal and the somatosensory cortices modulates according to the type of observed transitive actions. Specifically, these regions were more activated for the grasping than for the pointing condition. In contrast, the premotor cortex, a neural marker of action observation, did not show any differential activity when contrasting the considered experimental conditions. Our findings may provide novel insights regarding a possible role of extrastriate and somatosensory brain areas for the perception of distinct types of human hand-object interactions.