Medial prefrontal cortex dissociation between self and others in a referential task: An fMRI study based on word traits

• We measured brain activity during self and other referential tasks.
• We used two types of trait words defined by reaction time for each participant.
• Activation differed across self and other only in the slow word condition.
• The self-slow condition showed greater activation in the ventromedial PFC.
• The other-slow condition showed greater activation in the middle temporal gyrus.

A number of recent neuroimaging studies using self referential tasks have investigated whether self referential processing depends on a unique neural basis that operates specifically in the medial prefrontal cortex. However, these studies have provided contradictory results despite the use of similar methodologies. We hypothesized that these discrepancies are partially related to the task-difficulty that presents dissociations reaction times in the self- and other-referential tasks. We therefore measured brain activity during self and other referential tasks to determine if such activity can be dissociated according to the reaction times (fast versus slow) for the trait words. Activation differed across self and other only in the slow word condition. The self referential condition with slow reaction time produced greater activation in the ventromedial prefrontal cortex, whereas the other referential condition with slow reaction time produced activation of the middle temporal gyrus. Results suggested that the task-difficulty might affect whether or not brain activities within MPFC would be dissociated between self- and other-referential processing.