Abnormalities in the brain system subserving internally focused activity in schizophrenia and bipolar disorder may have important implications for understanding the emergence of aberrant mental states. This approach is promising because most psychopathology is not task-related, but rather arises spontaneously during interactions with the environment. Therefore, networks that modulate these spontaneous interactions are suitable foci of inquiry. For example, these findings may arise from abnormalities in long-tract signaling (Kubicki et al., 2007) and a breakdown in activity integration among multiple brain areas, ultimately manifesting as disordered processing of emotion, thought, or perception. Our current understanding of large-scale neural networks, however, is not sufficient to make predictions about which DMN abnormalities contribute to which clinical presentations. To this end, we need studies of large-scale neural networks which examine network characteristics under clinically relevant experimental conditions (Greicius 2008).
