The Electrophysiological Basis of Negative BOLD in Default Mode Network

Joanne R. Hale¹, Peter G. Morris¹, Matthew J. Brookes¹

The default mode network (DMN) has been widely investigated using BOLD fMRI; studies show it to be most active in the resting state with BOLD decreasing on task initiation. In this study, we employ parallel fMRI and magnetoencephalography (MEG) experiments to investigate electrophysiological processes that underlie negative BOLD changes. Using a working-memory task we characterise negative BOLD in DMN. Using MEG we show that marked decreases in high beta and gamma oscillations underlie negative haemodynamic change. Our study confirms a neural basis to BOLD in DMN, and adds weight to arguments suggesting that gamma oscillations and BOLD are intimately linked.