  While many human imaging methodologies probe the structural and functional
connectivity of the brain, techniques to investigate cortical networks in a
causal and directional manner are critical but limited. The use of iEEG enables
several approaches to directly characterize brain regions that are functionally
connected and in some cases also establish directionality of these connections.
In this chapter we focus on the basis, method and application of the
cortico-cortical evoked potential (CCEP), whereby electrical pulses applied to
one set of intracranial electrodes yields an electrically-induced brain
response at local and remote regions. In this chapter, CCEPs are first
contextualized within common brain connectivity methods used to define cortical
networks and how CCEP adds unique information. Second, the practical and
analytical considerations when using CCEP are discussed. Third, we review the
neurophysiology underlying CCEPs and the applications of CCEPs including
exploring functional and pathological brain networks and probing brain
plasticity. Finally, we end with a discussion of limitations, caveats, and
directions to improve CCEP utilization in the future.
