Standard and individually determined thermal pain stimuli induce similar brain activations.

BACKGROUND

Several functional magnetic resonance imaging (fMRI) studies use thermal pain stimuli to determine brain activation patterns during pain. Studies use either a standard temperature condition for all participants or an individualized temperature condition based on the individually determined pain threshold of the participant. The aim of the present study was to compare both conditions in the same participants.

METHODS

Eighteen healthy participants (21-29 years) underwent four fMRI runs, in each of which they received three types of thermal stimuli: neutral (32 °C), warm (37 °C) and painfully hot. In two runs, the painfully hot stimulus was set at a standard temperature of 46 °C; in the other two runs, the temperature was set at the subject's individual pain threshold (46-48 °C). fMRI (blood oxygen level dependent) was performed on a 1.5 T MR scanner (GE Signa). Pre-processing and statistical analyses were performed using Statistical Parametric Mapping (SPM8) software.

RESULTS

While the stimulation temperatures were lower in the standard temperature condition, both conditions activated the same brain regions. When comparing the conditions directly to each other, we did not find significantly different grey matter activation patterns.

CONCLUSIONS

The similar activation patterns between the two conditions suggest that it is not necessary to use individualized stimuli per se. The temperature of 46 °C appeared to be an adequate temperature for standardized stimulation to observe significant brain activations related to thermal pain.