Abstract
The purpose of this experiment was to examine the effects of the intensity of pain-eliciting stimulus and the variety of ISI (inter-stimulus interval) upon the ERPs (event related brain potentials) and the magnitude estimation of perceived pain.
Twenty payed undergraduates, 10 males and 10 females, served as subjects. Each subject received a total of 32 trials. In each trial, 20 electric pulse trains were given through the needle electrode which touched the skin of the back of right index finger. The mean ISI was 2 s. In the variable ISI condition, the ISI varied 1-3 s randomly. The intensity of the stimulus varied from 10 to 40 V with a 10 V step among trials.
The grand mean ERPs (Fig. 3) were shown to have two major components, EN (early negativity) with a peak latency of 120-140ms and LPC (late positive component) with a peak latency of 250-350ms. EN was dominant on Fz and LPC on Cz. The amplitude of LPC and the magnitude estimation of perceived pain significantly increased with the stimulus intensity. The amplitude of EN was significantly larger in variable-ISI condition than constant-ISI condition. It was suggested that the LPC of ERPs recorded from the central areas (Cz) seemed to be the best index of perceived pain.
