[Cognitive processes in unconscious patients? A brain mapping study of the P300 potential].

P300 is the most investigated component of the event-related potentials. Being the correlate of an active target discrimination and decision making process it is seen as related to cognition. Such elementary cognitive processes--as expressed in P300--can happen even in states of coma. In four of 35 comatose patients with diffuse head injury we were able to measure the P3-wave showing frontal and parietal components. Accordingly some unawakable patients can still recognize differences in pitch. The structure of components and their psychophysiological meaning are discussed.