We presented many trial-unique, relatively new, meaningless hand-finger actions without goals to observers to observe and to imitate during PET scanning. These actions were not trained before the experiment. The main results were that de activation in the prefrontal cortex was observed during imitation of hand-finger actions compared with the observation and the rest conditions. These results were discussed in relation to the problems of the self and the other in which the prefrontal cortex is involved. No activation was observed in Broca's area during observation and imitation of actions employed in the present experiment. A large number of trial-unique, new actions without goals may be responsible for the absence of activation in Broca's area.

Part 1: Brain and Evolution