Group average activation maps of functional MRI: Methodology of identifying group brain areas activated during painful thermal stimuli, motor and vibrotactile tasks in humans

Pain perception activates a complex network of cortical regions. The functional specializations of the various components comprising this network remain for the most part unknown. Moreover, the cortical networks described for pain perception include cortical regions involved in touch perception, and motor execution. We performed functional MR[ (fMRI) studies to compare between cortical networks activated during a thermal painful stimulation with cortical networks activated during vibrotactile, and motor tasks. The fMRI scans for all three tasks were done in every subject, in single scanning sessions. This procedure enables the comparison between activation maps in individual subjects. A group average activation map was necessary to compare our fMRI results with earlier positron emission tomography (PET) studies of thermal pain, most of which have been based on group averages, and in order to examine the task dependent brain activations within a population of normal subjects. Here we describe the methodology developed for generating fMRI population activation maps.