Temporal integration of pain from electrical stimulation of the skin.

The threshold of sensation and the threshold of pain in response to electrical stimulation (impulses of 1 msec duration) of the skin on the forearm or hand in individuals without pain were compared with the thresholds of individuals with chronic pain in the range 1 to 100 pulses per second repetition rate. The threshold of sensation in patients without pain was little affected by the repetition rate of the stimulation within the range studied, and the threshold for pain decreased exponentially with increasing repetition rate. In individuals with chronic pain the threshold of sensation was similar to that of individuals without pain over the entire range of stimulus repetition rates studied, but the threshold of pain in patients with pain was lower and less affected by the stimulus rate than it was in the individuals without pain, thus closer to the threshold of sensation.