fMRI pain activation in the periaqueductal gray in healthy volunteers during the cold pressor test

The periaqueductal gray (PAG), a brain area belonging to the descending pain modulatory system, plays a crucial role in pain perception. Little information is available on the relationship between PAG activation and perceived pain intensity. In this study, we acquired functional magnetic resonance imaging (fMRI) scans from the PAG during the cold pressor test, a model for tonic pain, in 12 healthy volunteers. fMRI data were acquired with a 12-channel head-coil and a 3-Tesla scanner and analyzed with Statistical Parametric Mapping (SPM8) software. During the cold pressor test, fMRI showed significant activation clusters in pain-related brain areas: bilateral middle and superior frontal gyrus, anterior cingulate cortex and thalamus, left insula, right inferior frontal gyrus, left inferior temporal gyrus and in the bilateral PAG (cluster level corrected threshold p