Fig. 1

Experimental paradigm. A computer-controlled infusion method was used to achieve propofol target effect-site concentrations of 1 and 3 μg/mL. The target effect-site concentration level was measured for 6 min and then increased to 3 μg/mL. Every 6-min observation period was divided into three phases, and each phase lasted for 2 min. TAES was administrated at the phases two and five, respectively