focused on the subgenual cingulate cortex (Mayberg et al., 2005), dorsolateral prefrontal cortex (for example see (Seminowicz et al., 2004)) and the default mode network (DMN). Reported functional connectivity abnormalities include decreased corticolimbic connectivity (especially with the dorsal anterior cingulate), increased connectivity within the DMN, especially in the subgenual prefrontal cortex, and decreased connectivity between DMN and caudate (Seminowicz et al., 2004; Anand et al., 2005a, 2005b, 2009; Greicius et al., 2007; James et al., 2009; Bluhm et al., 2009a). Increased subbgenual connectivity has been related to depression severity (Greicius et al., 2007), and algorithms based on functional connectivity can distinguish between depressed and control subjects (Craddock et al., 2009) and predict treatment response (Seminowicz et al., 2004). Similarly, EEG functional connectivity studies have suggested a role for a pathological global increase in functional connectivity within alpha and theta frequency bands (Fingelkurts et al., 2007), and that functional networks during sleep are topologically different in acutely depressed patients versus normal controls (Leistedt et al., 2009). Most intriguingly, a recent analysis applying graph theoretic techniques to resting-state fMRI functional connectivity data demonstrated a significant decrease in mean path length in depressed patients, primarily due to an increase in functional connectivity within
