Resting state brain connectivity of pain and fatigue is affected by performance of a fatiguing attention task in patients with chronic pain.

Fatigue is common in patients with chronic pain, but the neural underpinning of this symptom is still poorly understood. In this study, we aimed to investigate resting state connectivity correlates of pain and fatigue in patients with chronic pain. Twenty-four women with chronic pain, and 22 age-matched healthy controls underwent resting state functional magnetic resonance imaging (fMRI), performed a 20-min fatiguing attention task, and underwent an additional resting state fMRI examination. Patients with chronic pain reported a higher degree of both fatigue (p < 0.001) and pain (p < 0.001) than healthy controls. Significant group differences in connectivity to the lateral visual network, the salience network, the auditory network, the executive control network, and especially in regions within the default mode network were detected before the task. After the task, these differences were no longer statistically detectable, and only differences in connectivity between the basal ganglia network and the prefrontal areas between groups were observed. While differences in functional connectivity related to pain were present before performance of the task, only differences related to fatigue were found after the task. This finding indicates that processing of fatigue might overshadow processing of pain after performance of a fatiguing attention task in patients with chronic pain.