Group statistical comparison t maps (radiological convention; p<0.05, corrected), overlaid on high resolution anatomical images in Talairach space, showing in 11 healthy subjects significant differences in the brainstem during brush to either secondary area versus brush to the primary following heat/capsaicin application to the right ophthalmic division of the trigeminal nerve versus brush to the untreated skin of the same cutaneous territory. In blue are represented the clusters more activated during primary versus secondary dynamic mechanical allodynia, the opposite is true for the activation in the caudal medulla shown in yellow/red.
(MRF = medulla reticular formation; PRF = pons reticular formation; dlPAG = dorsolateral PAG; Med Thal = medial thalamus; IC = inferior colliculus).