The Cerebral cortex is part of the brain. This neurological location was where Ceti eels would wrap themselves around, in a humanoid host. This left said-host vulnerable to suggestion. As the eels grew, putting pressure on the cortex, the victim would experience maddening pain to the point of death. (TOS movie: The Wrath of Khan) The Tigan interface technology downloaded information directly into the cerebral cortex. (TNG comic: "History Lesson")