Investigating the Neural Basis of Pain Sensitivity in Fibromyalgia Using Functional Magnetic Resonance Imaging

Abstract

Fibromyalgia (FM) is a chronic pain condition that is estimated to affect 2-5% of the global population. The cause of FM is currently unknown, although most evidence suggests it involves central sensitization. To determine the underlying neurological mechanism of this central sensitization, researchers have started to study pain processing in people with FM using functional magnetic resonance imaging (fMRI). The results from these studies have been inconsistent and appear to be related to the fMRI analysis method that is used. Model-driven analysis methods have consistently identified little to no differences in neurophysiological activity associated with pain processing between healthy and FM study groups. On the other hand, data-driven methods have consistently identified differences between the two study groups. The overall aim of this thesis was to determine if data-driven analysis methods provide information about pain processing that model-driven methods do not, and to use a data-driven method to improve our understanding of the possible mechanisms underlying central sensitization in FM. For the first objective, a model-driven and a data-driven analysis method were compared by analyzing datasets from two separate fMRI pain studies involving healthy controls and participants with FM. The results from this comparison were consistent with what has already been reported—that is, the model-driven analyses did not identify differences in pain processing between the two study groups, and the data-driven analyses did. To improve our understanding of the neural basis of pain sensitivity in FM, healthy controls and participants with FM were subjected to an identical ‘threat/safety’ fMRI paradigm, and the results were analyzed with the same data-driven method. Differences in brain activity between the two study groups were identified. Furthermore, the FM-specific brain activity suggests that central sensitization in FM is likely associated with dysfunctions in brain regions involved in the motivational-affective aspects of pain processing. These results emphasize the importance of data-driven analyses when studying pain processing and highlight aspects of pain processing specific to FM that deserve further investigation.