Human Posterior Insula Functional Connectivity Differs Between Electrical Pain and the Resting State.

The objective in this study was to directly compare MRI-based functional connectivity between conditions of rest and painful electrical nerve stimulation for key regions involved in pain processing: the anterior and posterior insula and the anterior cingulate cortex. Electric nerve stimulation, rated 7/10 for pain, was delivered to the right index finger of 14 healthy pain-free adult volunteers in four 30-sec blocks and continuously for 2 min. Functional connectivity maps obtained at rest and during both pain tasks were compared using seed time courses from the left anterior and posterior insula and anterior cingulate. Significant Pain versus Rest connectivity differences were consistently shown for the posterior insula, notably to the posterior cingulate and precuneus, while minimal and inconsistent differences were observed for the anterior insula and anterior cingulate. This study reinforces the known differences that can occur with changes in seed region selection in functional connectivity analysis. It also presents preliminary evidence that functional connectivity for the left posterior insula can potentially differentiate the presence of acute right-sided electrical pain from the nonpainful resting state.