Functional MRI Study of Pressure Pain and Its Modulation Using Mental Imagery
Principal Investigator: Charles S. Cleeland, Ph.D.
This study used functional magnetic resonance imaging (fMRI) to map areas of activation in the brain due to pain, and to assess the changes in the levels of activation when the perceived level of pain was modulated by mental imagery.
- To measure the changes in blood flow that occur in the brain during the presentation of an experimental pain stimulus (Complete)
- To determine whether these changes in blood flow are affected by the use of mental imagery to decrease the pain (Complete)
- To determine if there is a dissociation between the effects of mental imagery on the perceived "intensity" and "unpleasantness" of pain (Complete)
In this study, the pressure algometer was used to induce pain in human volunteers. To experience pain using the pressure algometer, the volunteer places his or her index finger in a plexiglass apparatus and a weight is placed on top of it.
This is a within-subjects design. Each subject received one fMRI scanning session that included three different pain conditions: "control", "toward" and "away." In the "control" condition, the subject was verbally instructed to imagine the non-weighted pressure algometer as painful. During the "toward" condition, the subject was verbally instructed to focus on the pain resulting from the application of the weighted algometer. During the "away" condition, the subject was distracted from the pain using verbally-cued mental imagery.
The intensity and unpleasantness of pain are measured separately using 0-10 self-report scales. Brain activation is measured by the changes in blood flow observed in fMRI scans.
The subjective mean post-experiment rating of pain intensity was 2.9 in the away state and 6.5 in the toward state. As a comparison, the mean rating in the pre-imaging session (without verbal cueing to focus toward or away from the pain) was 5.4.
This study demonstrated the utility of fMRI for the evaluation of the cortical representation of pain and its modulation by mental imagery, and reinforced previous studies that have demonstrated the involvement of the anterior cingulate cortex and insular cortex in the processing of painful stimuli. The use of fMRI in studies of pharmacological and behavioral interventions should provide a powerful tool for studying the poorly understood mechanisms responsible for the effects of these interventions.
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