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

Abstract

Functional magnetic resonance imaging (fMRI) was used to localize brain areas
\nthat were active during the observation of actions made by another individual.
\nObject- and non-object-related actions made with different effectors (mouth, hand
\nand foot) were presented. Observation of both object- and non-object-related
\nactions determined a somatotopically organized activation of premotor cortex. The
\nsomatotopic pattern was similar to that of the classical motor cortex homunculus.
\nDuring the observation of object-related actions, an activation, also
\nsomatotopically organized, was additionally found in the posterior parietal lobe.
\nThus, when individuals observe an action, an internal replica of that action is
\nautomatically generated in their premotor cortex. In the case of object-related
\nactions, a further object-related analysis is performed in the parietal lobe, as 
\nif the subjects were indeed using those objects. These results bring the previous
\nconcept of an action observation/execution matching system (mirror system) into a
\nbroader perspective: this system is not restricted to the ventral premotor
\ncortex, but involves several somatotopically organized motor circuits.