Exploratory study of the effect of brain tumors on the default mode network

Resting state functional magnetic resonance imaging (RS-fMRI) is a popular method of visualizing functional networks in the brain. One of these networks, the default mode network (DMN), has exhibited altered connectivity in a variety of pathological states, including brain tumors. However, very few studies have attempted to link the effect of tumor localization, type and size on DMN connectivity. We collected RS-fMRI data in 73 patients with various brain tumors and attempted to characterize the different effects these tumors had on DMN connectivity based on their location, type and size. This was done by comparing the tumor patients with healthy controls using independent component analysis (ICA) and seed based analysis. We also used a multi-seed approach described in the paper to account for anatomy distortion in the tumor patients. We found that tumors in the left hemisphere had the largest effect on DMN connectivity regardless of their size and type, while this effect was not observed for right hemispheric tumors. Tumors in the cerebellum also had statistically significant effects on DMN connectivity. These results suggest that DMN connectivity in the left side of the brain may be more fragile to insults by lesions.