Predicting pain: differential pain thresholds during self-induced, externally induced, and imagined self-induced pressure pain

During self-induced pain, a copy of the motor information from the body's own movement may help predict the painful sensation and cause downregulation of pain. This phenomenon, called sensory attenuation, enables the distinction between self-produced stimuli vs stimuli produced by others. Sensory attenuation has been shown to occur also during imagined self-produced movements, but this has not been investigated for painful sensations. In the current study, the pressure pain thresholds of 40 healthy participants aged 18 to 35 years were assessed when pain was induced by the experimenter (other), by themselves (self), or by the experimenter while imagining the pressure to be self-induced (imagery). The pressure pain was induced on the participants left lower thigh (quadriceps femoris) using a handheld algometer. Significant differences were found between all conditions: other and self (P < 0.001), other and imagery (P < 0.001), and self and imagery (P = 0.004). The mean pressure pain threshold for other was 521.49 kPa (SE = 38.48), for self 729.57 kPa (SE = 32.32), and for imagery 618.88 kPa (SE = 26.67). Thus, sensory attenuation did occur both in the self condition and the imagery condition. The results of this study may have clinical relevance for understanding the mechanisms involved in the elevated pain thresholds seen in patients with self-injury behavior and the low pain thresholds seen in patients with chronic pain conditions. Imagery of sensory attenuation might also be used to alleviate the pain experience for patients undergoing procedural pain.