Consciousness in Coma?

Are coma patients still able of cognition and emotion and to what extend? Such questions can be investigated with auditory Event-Related Potentials (ERPs) and Skin Conductance Response (SCR). Cognitive functions were tested with several paradigms in 44 coma patients and emotional response in fifteen of them. In at least 7 % (N=44) of these patients an explicit semantic processing and thus a minimal remaining consciousness could not be excluded. This study is the first to demonstrate semantic processing in coma. We found a correlation between emotional SCR and level of consciousness as measured by the GCS and the Cook and Palma scores in agreement with the weak emotional SCR observed in these patients. Some ERPs, when observed in coma have also a prognosis value. We conducted a meta-analysis on 337 to 612 patients showing that the N100, the Mismatch Negativity, and the P300 predict awakening from coma. This work provides new insights on the coma state and suggests new methods of assessment of these patients for medical practitioners.