Modulation of medial prefrontal and inferior parietal cortices when thinking about past, present, and future selves.

Recent functional neuroimaging studies have shown that reflecting on representations of the present self versus temporally distant selves is associated with higher activity in the medial prefrontal cortex (MPFC). In the current fMRI study, we investigated whether this effect of temporal perspective is symmetrical between the past and future. The main results revealed that the MPFC showed higher activity when reflecting on the present self than when reflecting on past and future selves, with no difference between past and future selves. Temporal perspective also modulated activity in the right inferior parietal cortex but in the opposite direction, activity in this brain region being higher when reflecting on past and future selves relative to the present self (with again no difference between past and future selves). These findings show that differences in brain activity when thinking about current versus temporally distant selves are symmetrical between the past and the future. It is suggested that by processing degrees of self-relatedness, the MPFC might sustain the process of identifying oneself with current representations of the self, whereas the right inferior parietal cortex might be involved in distinguishing the present self from temporally distant selves.