A PET investigation of the attribution of intentions with a nonverbal task.

Several authors have demonstrated that theory of mind is associated with a cerebral pattern of activity involving the medial prefrontal cortex. This study was designed to determine the cerebral regions activated during attribution of intention to others, a task which requires theory-of-mind skills. Eight healthy subjects performed three nonverbal tasks using comic strips while PET scanning was performed. One condition required subjects to attribute intentions to the characters of the comic strips. The other two conditions involved only physical logic and knowledge about objects' properties: one condition involved characters, whereas the other only represented objects. The comparison of the attribution of intention condition with the physical logic with characters condition was associated with rCBF increases in the right middle and medial prefrontal cortex including Brodmann's area (BA) 9, the right inferior prefrontal cortex (BA 47), the right inferior temporal gyrus (BA 20), the left superior temporal gyrus (BA 38), the left cerebellum, the bilateral anterior cingulate, and the middle temporal gyri (BA 21). The comparison of the physical logic with characters condition and the physical logic without characters condition showed the activation of the lingual gyri (BA 17, 18, 19), the fusiform gyri (BA 37), the middle (BA 21) and superior (BA 22, 38) temporal gyri on both sides, and the posterior cingulate. These data suggest that attribution of intentions to others is associated with a complex cerebral activity involving the right medial prefrontal cortex when a nonverbal task is used. The laterality of this function is discussed.