dMRI (jointly with traditional MRI) provides a detailed anatomical view of the brain. It allows the recovery of the fiber structure of the white matter: these are the electrical connexions between distant cortical areas. But dMRI does not provide any clue on:
- the connexions may be incomplete and/or erroneous,
- the actual use of connexions during brain activity,
- the actual communication pattern along time for a given task.
On the opposite, EEG and MEG (jointly named MEEG) provide (after source reconstruction) time courses of the activity of the cortical areas. It is possible to recover some connectivity information from these time courses, but these are purely signal-based and do not take into account the anatomy, so that the results are often ambiguous. Furthermore, the regularization that is used for source reconstructions is based on mathematical a priori, and does not benefit from knowledge on actual brain structure.