In mania, the DMN is characterized by abnormalities in key nodes of the limbic system (mPFC and hippocampus) where abnormalities have been documented in bipolar disorder (Öngür and Price 2000). At the same time, lateral parietal areas show synchronous activity with the DMN, and a nearby although not identical region is correlated with the level of manic symptomatology (as measured by the YMRS). Reduced coherence in limbic regions and increased coherence in other cortical regions may be consistent with the dysregulated emotional processing and increased goal directed activities seen in mania (Strakowski et al., 2005; Phillips et al., 2003). Consistent with the involvement of this brain region in bipolar disorder, manic episodes have been reported following lesions of the parietal cortex (Fenn and George 1999). The finding of greater than normal coherence within the V1 component in bipolar disorder suggests that the inappropriate recruitment of posterior cortical regions into large-scale neural networks is not restricted to the DMN in this condition. This suggestion is also consistent with previous findings of visual processing abnormalities in bipolar disorder (Chen et al., 2006; Miller et al., 2003).
