Warm-, hot- and pain-related neural activities depending on baseline skin temperatures.

BACKGROUND: This study investigated the characteristics of temperature-related evoked neural activities to baseline skin temperatures on target and adjacent sites using contact heat evoked potentials (CHEPs).

METHODS: Contact heat evoked potentials were recorded from 12 normal subjects during three stimuli: target temperatures for "warm", "hot" and "pain" were set at 41, 46 and 51 °C, respectively. The baseline temperature was separately set at 30, 35 and 40 °C under all conditions, and a heat pulse was delivered over the right forearm at 41 °C under the warm condition, at 46 °C under the hot condition and at 51 °C under the pain condition.

RESULTS: The N2-P2 amplitude was significantly larger at the 40 °C baseline than at the 30 and 35 °C baselines during the pain condition, whereas no significant differences were observed during the hot and warm conditions. In addition, the effects of an interference warm stimulation to adjacent sites were examined; however, no significant effects were observed.

CONCLUSIONS: These results suggest that the priming effects of temperature on CHEPs were only observed under the pain condition, indicating the specificity of thermal pain, as well as a difference in the neural mechanisms responsible for thermal noxious and innocuous processing in human brains.

SIGNIFICANCE: This study using CHEPs shows the importance of baseline and target skin temperatures to investigate the characteristics of temperature-related neural activities. This measure may contribute to understanding of warm-, hot-, and pain-related neural activities in human brains.