The P300 event-related brain potential as an indirect index of pain in a dual-task paradigm

My dissertation examines the utility of the P300 event-related brain potential (ERP) as an objective, indirect index of pain in a dual-task paradigm. The primary task consisted of either experiencing ischemia-induced pain or feigning pain, and the secondary task was a 3-stimulus auditory discrimination to which ERPs were recorded (target oddballs (p =.1), nontarget distractors (p =.1), nontarget frequents (p =.8)). Real pain, but not feigned pain, was conceptualized as an inherently attention-absorbing task which decreases attentional resources. It was hypothesized that the P300s of the real-pain subjects, but not those of the feigned-pain subjects, would decrease during the pain conditions.;Results of the first experiment showed that the monetarily-motivated feigned-pain subjects were able to decrease their P300 amplitudes comparable to those of the real-pain subjects, but there were other unexpected real- versus feigned-pain differences. An individual classification rate of 79% (22/28) was obtained using multiple P300 and behavioral measures in a discriminatory analysis.;In a second experiment, I attempted to limit the ability of subjects to feign pain. An additional letter-repetition task was performed during the tone intertrial interval, in order to make it more difficult for the subjects to feign pain. In this study, an individual classification rate of 73% (8/11) was obtained using multiple P300 measures in a discriminatory analysis. However, different real- versus feigned-pain P300 effects were obtained in comparison to the results of the first experiment. It was hypothesized that the additional letter-repetition task caused these unexpected changes.;Therefore, in the third experiment I investigated the effects of the letter-repetition task within-subjects. ERPs were recorded in two conditions in which (1) subjects performed the auditory discrimination task alone, and (2) subjects simultaneously performed both the auditory discrimination and letter-repetition tasks. (There were no pain manipulations.) Results indicated that the addition of the letter-repetition task caused both P300 amplitude and latency changes.;I conclude that the P300 event-related potential objectively discriminates real- from feigned-pain subjects.