Effects of attention on the intensity and unpleasantness of thermal pain.

Both experimental and clinical studies have shown that psychological manipulations, such as hypnosis, behavioral modification and cognitive-behavioral therapy, can reduce reports of pain. Although these are complex procedures, one important variable common to each is direction of attention. We have previously demonstrated in both humans and monkeys a method for monitoring and manipulating attention toward or away from a painful stimulus and have shown that changes in the direction of attention alter the ability to discriminate noxious heat stimuli. The present study assessed whether these changes in discrimination were accompanied by changes in the perception of pain intensity and/or unpleasantness. These data confirm that both the speed and accuracy of detecting changes in noxious heat stimuli are decreased when the subject attends to another stimulus modality. In addition, they show that direction of attention affects the perceived intensity and unpleasantness of painful stimuli in a similar manner. Our previous findings of attention-related modulation of nociceptive neuronal activity in the medullary dorsal horn suggest that these attention-dependent changes in sensory-discriminative and affective components of pain are mediated at early stages of sensory processing.