Action observation activates premotor and parietal areas in a somatotopic manner: an fMRI study

Functional magnetic resonance imaging (fMRI) was used to localize brain are as that were active during the observation of actions made by another indiv idual. Object- and non-object-related actions made with different effectors (mouth, hand and foot) were presented. Observation of both object- and non -object-related actions determined a somatotopically organized activation o f premotor cortex. The somatotopic pattern was similar to that of the class ical motor cortex homunculus. During the observation of object-related acti ons, an activation, also somatotopically organized, was additionally found in the posterior parietal lobe. Thus, when individuals observe an action, a n internal replica of that action is automatically generated in their premo tor cortex. In the case of object-related actions, a further object-related analysis is performed in the parietal lobe, as if the subjects were indeed using those objects. These results bring the previous concept of an action observation/execution matching system (mirror system) into a broader persp ective: this system is not restricted to the ventral premotor cortex, but i nvolves several somatotopically organized motor circuits.