What Are the Advantages and Challenges of Simultaneous Scalp EEG and Intracranial EEG Data Recording?

Scalp and intracranial electroencephalography are both based on the recording of field potentials, i.e., electrical potentials in the extracellular space. Thanks to recent technological developments, simultaneous recordings of EEG and iEEG provide complementary information to understand brain functions. The relationship of the cortical source activity with their scalp and intracranial EEG correlates is still not very well known. Since some cortical sources are not directly visible in scalp EEG recordings, it gives the false impression of no electrical contribution and thus that scalp electrodes are unnecessary. In this chapter, I illustrate the importance to record and precisely analyze scalp EEG in combination with intracranial EEG. First, the technical challenges imposed by combination of the two EEG methods are described. Then, historical aspects and the main findings of the first simultaneous scalp and intracranial EEG recordings since the mid-1950s are presented. Finally, applications and future perspectives in cognitive, clinical, and computational neuroscience are discussed.