Objectives: To evaluate cortical information processing (particularly, semantic processing) in acute nontraumatic coma by means of event-related brain potentials (ERPs).
Methods: The tests included measures of obligatory auditory processing (N100), automatic (Mismatch Negativity) and controlled (P300) detection of stimulus deviance, and semantic processing (ERP effects in word pairs and sentences). The tests were presented to 20 healthy participants and 42 coma patients with Glasgow Coma Scale <9.
Results: Responders (ie, patients whose ERP data indicate that their brain was able to process the corresponding stimuli) were found in each ERP test, and their distribution was statistically different from that expected by chance. Particularly, 7 responders were found in the word pair paradigm and 3 responders in the sentence paradigm. The P300 responsiveness highly correlated with other ERP responses, with Glasgow Coma Scale and with the future development of coma (ie, P300 on day 4 was related to the clinical state on day 20).
Conclusions: Results suggest a wide range of cortical information processing in coma, including semantic processing. The question is discussed of whether, and to what extent, these processing operations are related to conscious awareness of stimuli.