In an exploratory analysis, we also identified alterations in BOLD signal timecourse within the DMN in bipolar disorder and schizophrenia. Spontaneous neuronal oscillations are a major feature of brain networks, and they support the representation and consolidation of information (Buzsaki and Draguhn 2004). Low frequency oscillations are dysregulated in bipolar disorder and schizophrenia, suggesting significant abnormalities in underlying brain circuits and increased noise in the network. Bipolar disorder subjects showed a more extreme pattern, where very low frequency power was reduced and high frequency (>0.1 Hz) power was increased. There was no relationship between manic or psychotic symptoms and timecourse abnormalities, perhaps due to small sample size or because timecourse abnormality is a trait-like feature of mania.
