Analysis of connectivity in the resting state of the default mode of brain function: a major role for the cerebellum?

Low frequency (< 0.1 Hz) oscillations in resting state fMRI signal have been studied for some years and are now attracting interest in terms of their relationship to the so-called 'default mode' of the brain. The default mode network is identified as those brain areas which are active during rest and is believed to be associated with background environmental surveillance. In this study, we carry out a comprehensive analysis of the default mode network in the resting state across the whole brain, using a combination of model-based and data-driven approaches: a cosine basis set approach, the independent component analysis (ICA) and functional connectivity analysis. The correlated regions with low frequency fluctuations revealed by all three methods include a number of key nodes of the proposed default-mode network. Most importantly we have also identified the cerebellum and angular gyrus as possible major default mode nodes.