When Ruth looked at the scans of her normal subjects, she found activation of DSN regions that previous researchers had described. I like to call this the Mohawk of self-awareness, the midline structures of the brain, starting out right above our eyes, running through the center of the brain all the way to the back. All these midline structures are involved in our sense of self. The largest bright region at the back of the brain is the posterior cingulate, which gives us a physical sense of where we are—our internal GPS. It is strongly connected to the medial prefrontal cortex (MPFC), the watchtower I discussed in chapter 4. (This connection doesn’t show up on the scan because the fMRI can’t measure it.) It is also connected with brain areas that register sensations coming from the rest of the body: the insula, which relays messages from the viscera to the emotional centers; the parietal lobes, which integrate sensory information; and the anterior cingulate, which coordinates emotions and thinking.
