Responsiveness test and classification of the state of consciousness
During the experiment, the subjects were lying on bed with custom-made response handles secured to their wrists. Responsiveness was tested with a standardized prerecorded auditory request “press the handles twice” (R-test). Responding was practiced before the anesthesia. The R-test was presented with Presentation 17.0 stimulus delivery and experimental control software system (Neurobehavioral Systems Inc), and stimuli were delivered via headphones. The request was presented once at 2.5-min intervals throughout the experiment. A response to the R-test categorized the subject as responsive for the subsequent 2.5-min period. No response to R-test resulted in the subject being classified as unresponsive for the subsequent 2.5-min period.Targeting an ECThe categorization of subjects as connected or disconnected was based on (1) responsiveness classification and (2) structured interviews conducted at the end of the treatment period (