The impact of gliomas on resting-state oscillatory activity and connectivity: A magnetoencephalography study

Gliomas disturb brain functions, contributing to abnormal neuronal activity and connectivity changes that can be effectively investigated using magnetoencephalography (MEG). In this work, we used MEG to evaluate frequency-specific alterations of brain activity and functional connectivity in glioma patients. Two consecutive 5-min sessions of eyes-closed resting-state brain activity were recorded from ten glioma patients and ten age-matched healthy subjects. Modulations of power and functional connectivity, within the patient group and between patients and the healthy control group, were assessed in terms of the Neural Activity Index and the Multivariate Interaction Measure, respectively. These quantities were calculated in individualized frequency bands (delta, theta, lower alpha, upper alpha and beta) to account for changes in spectral peaks in patients. We report a decrease in power in tumor and peri-tumor regions in the upper-alpha and beta bands with respect to the rest of the brain, paired to a decrease in lower and upper-alpha band functional connectivity of the tumor and peri-tumor regions. In comparison with healthy subjects, we observe a global enhancement in power in lower-alpha in patients. Overall, our study shows that glioma infiltration can widely influence brain local and long-range synchrony in an individualized frequency-specific manner.