Optimizing the measurement of contact heat evoked potentials.

Our aim was to determine whether single trial averaging could improve quantification of contact heat evoked potentials measured from fixed position contact heat stimulation. Event-related brain potentials were measured in response to contact heat stimuli applied to the arm and the leg of 10 subjects via a circular thermode, using fixed and varied thermode positions at 41 degrees C and 51 degrees C. Contact heat evoked potentials were successfully recorded from varied position stimulation of the leg at 51 degrees C in 80% of subjects, but from only 60% of subjects using a fixed position. Contact heat evoked potentials were only identified in a small number of subjects when stimulating at 41 degrees C. The amplitude of the N2-P2 complex and pain intensity ratings were larger for the varied compared with the fixed thermode position and were also larger when stimulating the arm. Automated single trial analysis of the data resulted in larger amplitude of the N2-P2 complex than standard averaging. In conclusion, we have demonstrated that the reduced contact heat evoked potentials amplitude seen for fixed location stimulation can be improved with single-trial averaging.