Thursday 20 March 2014

The EEG view of the default mode network

Studies of self-referential processing and mind wandering point to the role of the default mode network (DMN), which is prominent when there are no task domains.  Most recent studies of the DMN use fMRI.  An interesting study of the DMN was done by Chen et al (2008) with EEG.  Using a high density 128 channel array, 15 healthy female subjects were tested in eyes-closed and eyes-open conditions and given no other instructions than to relax, the idea being that this would represent the DMN.

According to the authors, their findings show
...the dominant spectral field powers entails a constellation of large low-frequency delta activity at the prefrontal area, much smaller theta activity at fronto-central area, alpha-1 activity at the anterior-posterior area, alpha-2 and beta-1 at the posterior area, and high-frequency beta-2 and gamma activities at the prefrontal area. Compared to the eyes-open resting state, the delta field power is enhanced at the prefrontal area while the theta, alpha-1, alpha-2 and beta-1 powers are reduced in the respective areas. Greater inter-individual variability in field power can be seen in the eyes-closed than the eyes-open state. In the eyes-closed state, the prefrontal delta field power is correlated with both beta-1 and gamma field powers, while these two high-frequency field powers are mutually correlated at the same area.

This study provides a useful reference point for understanding what the DMN looks like in terms of EEG, and, in particular, the findings can be useful in interpreting the fMRI and EEG studies of what occurs in meditation.

Chen, A. C., Feng, W., Zhao, H., Yin, Y., & Wang, P. (2008). EEG default mode network in the human brain: spectral regional field powers. Neuroimage41(2), 561-574.

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