EFFECTS OF OPERANTLY CONDITIONING THE AMPLITUDE OF THE P200 PEAK OF THE SEP ON PAIN SENSITIVITY AND THE SPINAL NOCICEPTIVE WITHDRAWAL REFLEX IN HUMANS

This study attempted to replicate and extend earlier work that reporte d that the amplitude of the P200 peak of the human somatosensory evoke d potential (SEP) can be increased and decreased when reward is made c ontingent upon change and that these changes are accompanied by altera tions in pain sensitivity. Twenty-one subjects were able to make the a mplitude of the P200 peak evoked by sural nerve stimulation larger dur ing increased training (up-training) than during decreased training (d own-training). There were no differences in the sural nerve compound a ction potential between up-training and down-training. This finding de monstrates that the change in P200 amplitude was not due to a change i n stimulus efficacy, but rather to a change within the central nervous system. Subjective pain ratings and a nociceptive spinal reflex were the same in up-training as in down-training. Thus, conditioned changes in P200 amplitude do not alter pain sensitivity.