The role of medial prefrontal cortex in processing emotional self-referential information: a combined TMS/fMRI study

In this study we investigate the neural basis of emotional content in self-referential processing by using a combination of off-line repetitive Transcranial Magnetic Stimulation (rTMS) applied to the medial prefrontal cortex (mPFC) and whole-brain functional Magnetic Resonance Imaging (fMRI).We applied effective or ineffective (sham) 1-Hz rTMS to the mPFC of 14 healthy participants who immediately thereafter underwent fMRI while performing a personality attribution task to self or to others. rTMS produced an increase in the participants' reaction time (≈ 60 msec) when processing negative attributes. The neuroimaging findings indicated the involvement of a network of cortical nodes distant from those at the stimulation site; these distant nodes showed task-specific changes in blood oxygen level-dependent (BOLD) activity after effective TMS. The posterior cingulate cortex seemingly encoded the negative dimension of stimuli, but it did not differentiate between self or other. On the contrary the left angular gyrus and the left anterior temporal cortex showed changes indicating encoding of negative self-directed categorization. The mPFC region did not show effects of rTMS along the self-other dimension, but only along the affective dimension. The results indicate that the mPFC is a pivotal node in a cortical network that supports affective referential reasoning. Therefore, a key function of mPFC seems to be related to the processing of negative attributes. In the other nodes of the network the two dimensions of self-other attribution and affective attribution are partially independent, but largely overlapping with different degrees of local specialization.