Mapping and Tracking the Flow of Brain Activations using MEG/EEG: Hypothesis and Methods

We introduce a mathematical tool for the exploration of spatiotemporal dynamics of brain activations as revealed by time-resolved brain mapping techniques. In that respect, Magneto (MEG) and Electroencephalography (EEG) source imaging has been considerably maturing in terms of leading access to the dynamics of brain activity. Here we suggest that the local analysis in space and time of the resulting source measures might be performed through the computation of a cortical displacement field within the optical flow framework. The theoretical principles of the method are briefly introduced and are subsequently illustrated by simulations. Finally, this technique was applied on brain image sequences from a ball-catching paradigm, in which significant structures of the resulting optical flow during the early brain response that accompanied the fall of the ball could be revealed.