Tracing toothache intensity in the brain.

Identification of brain regions that differentially respond to pain intensity may improve our understanding of trigeminally mediated nociception. This report analyzed cortical responses to painless and painful electrical stimulation of a right human maxillary canine tooth. Functional magnetic resonance images were obtained during the application of five graded stimulus strengths, from below, at, and above the individually determined pain thresholds. Study participants reported each stimulus on a visual rating scale with respect to evoked sensation. Based on hemodynamic responses of all pooled stimuli, a cerebral network was identified that largely corresponds to the known lateral and medial nociceptive system. Further analysis of the five graded stimulus strengths revealed positive linear correlations for the anterior insula bilaterally, the contralateral (left) anterior mid-cingulate, as well as contralateral (left) pregenual cingulate cortices. Cerebral toothache intensity coding on a group level can thus be attributed to specific subregions within the cortical pain network.