Semantic processing in comatose patients with intact temporal lobes as reflected by the N400 event-related potential

The present study aimed at determining whether the N400 effect (an ERP index of semantic processing) for spoken words occurs in comatose patients. The patients, treated in an intensive care unit, scored less than 8 points in the glasgow coma score at the time of the recording. Semantically related and unrelated spoken word pairs were delivered to patients through headphones at a rate of 1/3 s. Patients with an intact temporal lobe exhibited differential N400-like responses for semantically related and unrelated word pairs, which suggests that word semantics can be processed even in the comatose state. In contrast, patients with an injured temporal lobe showed no such effect.