Functional Magnetic Resonance Imaging of the Human Brainstem and Cervical Spinal Cord during Cognitive Modulation of Pain.

Pain is a complex sensory experience, and cognitive factors such as attention can influence its perception. Modulation of pain involves a network of subcortical structures; however, the role and relationship of these regions in cognitive modulation of pain are not well understood. The aims of this research were to evaluate the behavioral effect of cognitive modulation of pain and investigate the neural correlates of this mechanism in the brainstem and cervical spinal cord (SC), using functional magnetic resonance imaging (fMRI) and structural equation modeling (SEM). We applied noxious thermal stimulation on the C6 dermatome to 12 healthy female participants while they performed the n-Back task. Our findings demonstrate a significant attenuation in pain perception across the group as a result of the task, along with high intersubject variability in the degree of modulation. Using fMRI, our studies characterize neural responses in subcortical regions that are involved in the modulation of pain. SEM analysis reveals connectivity between the brainstem and SC at the group and individual levels, depending on cognitive load and degree of pain modulation, respectively. All together, our research demonstrates the behavioral effect of cognitive modulation on pain and provides insight into the subcortical neural response to the process.