Sleep is divided into REM and NREM, which is further divided into Stages 1 through 3. In the deepest levels of sleep, how does the connectivity between the medial prefrontal and anterior cingulate cortex, the left and right inferior parietal cortex (IP), and the posterior cingulate (PC) change?
a) It is weakened
b) It is strengthened
c) There is no change
d) Additional brain areas come online