Abstract
Purpose: To analyze the principles that guide inference of covert cognitive functions and consciousness in patients with extremely severe brain damage on the basis of neurophysiological test results. Methods: (1) A quantitative analysis of a range of possible inferences based on neurophysiological findings in low- and non-responsive patients; (2) a logical analysis of the various possible orders of application of neurophysiological tests in such patients. Results: Surprisingly, improvement of neurophysiological test qualities contributes to the improvement of diagnostic results less than some other factors, such as the structure of the patient population, the quality of the previous clinical diagnosis, and the variability of the methods used. Conclusions: A sequential decision procedure is suggested. Different test paradigms should be combined most effectively to arrive at a reliable evaluation of cognitive functions in this patient population.