Hysteresis of slow-wave activity saturation but not behavioral responsiveness. Cumulative distribution functions of the concentrations associated with (A) loss and recovery of behavioral responsiveness (LOBR and ROBR) and (B) slow-wave activity saturation (SWAS) on induction and emergence from propofol anesthesia. A comparison for 50% of volunteers indicates a significant hysteresis in the concentration required to achieve slow-wave activity saturation (Ce_SWAS) but not for behavioral responsiveness. The data in (B) correspond to the mean Ce_SWAS for all 31 electroencephalogram channels for each of the 16 individuals who participated in study 1.