[Clinical epileptology and clinical system neuroscience: two sides of the same coin]

It is the cortices and the cortico-cortical connections that are involved in manifestation of normal cortical functions as well as production of seizure symptoms. In this sense, presurgical evaluation of patients with intractable partial epilepsy helps us delineate cortical functions and networks at the individual level. In return, the advancement of clinical system neuroscience brought us better understanding and evaluation of clinical epileptology as follows. Electrical cortical stimulation in epilepsy surgery can delineate the cortex responsible for a particular task by making transient focal functional impairment, which is in sharp contrast to chronic stroke lesions that are relatively large and usually associated with cortical plastic compensation. For example, this gold-standard mapping method recently demonstrated the presence of anterior ventral language pathway by revealing active engagement of the anterior part of the superior temporal gyrus in speech perception. Cortico-cortical evoked potential (CCEP) is a new in vivo electrical tract tracing method for presurgical evaluation. It promises to refine our understanding of surgical candidacy, first through a more precise and tailored evaluation of the seizure network in each individual patient, and second through greater understanding of the functional systems of the brain involved, such as language, praxis and cognitive motor control.