Behavioral results. A, Ratings of anxiety during presentation of signals HA and LA before the onset of pain LT (bench control group, mean ± one SEM). B, Heart rate changes during presentation of signals HA and LA (scanner group, mean ± one SEM). C, Ratings of perceived pain intensity in conditions LT/LA, LT/HA, and HT/HA (scanner group, mean ± one SEM).