C- and A delta-fibre mediated thermal perception: response to rate of temperature change using method of limits

Studies investigating the effect of rate of temperature change on thermal t hresholds have used a variety of different methods and threshold combinatio ns, and many display incomplete reporting of statistical analyses. It has b een suggested that C- and A delta -fibre mediated thresholds differ in thei r reaction to different rates of temperature change. Ten healthy female vol unteers (aged 18-26 years; mean 21 +/- S.D. 2.53) undertook cold sensation (CS), warm sensation (WS), cold pain (CP) and heat pain (HP) threshold dete rminations on the thenar eminence of the dominant hand. Rates of temperatur e change of 0.5, 1, 2.5 and 4 degreesC/s were used, with a modified method of limits. Adaptation temperature was 32 degreesC and thermode size 3 cm x 3 cm. Results showed a significant increase in WS, HP and CP thresholds wit h increased rates of temperature change (all p < 0.001), but no significant change for CS (p = 0.653). These results suggest that thresholds with a C- fibre component (WS, HP and CP) and those that are Ad-fibre mediated (CS) b ehave differently. A traditional explanation of measurement artefact alone is insufficient in rationalizing these results, with additional factors pot entially involved. Slow rates of temperature change were shown to reduce me an intra-individual differences in recorded threshold values, and also to a bolish ceiling effects with HP threshold determinations. Clinically, theref ore, using slow rates of temperature change with method of limits has a ran ge of benefits over and above simply minimizing measurement artefact.