Background & Aims
A growing body of research suggests visual network structures are implicated in pain processing and placebo conditioning. For example, previous literature indicates changes in functional connectivity in occipital regions are associated with the degree of pain relief and recovery rate from delayed-onset muscle soreness. However, how the function of visual network structures may underlie pain processing and expectancy-based placebo manipulation remains poorly understood. This current study aimed to investigate the task-dependent functional connectivity of the visual network during painful stimulation and to characterize the changes in task-dependent functional connectivity after administration of a placebo cream.
Methods
Fifty-five healthy pain-free adults over the age of 18 (M = 22.8, SD = 7.75) were recruited (65.5% women). Participants completed a baseline pain administration followed by a session with a topical placebo cream. During the placebo session, participants were given an expectancy-enhancing instruction set. Painful heat stimulation was assessed via a 0-100 visual analog scale (VAS). Painful heat stimuli were applied to the thenar eminence of the right palm using an fMRI-safe thermode. Stimulus intensity was individually calibrated to produce a 40 out of 100 pain rating on the VAS. Participants completed approximately 12 functional scans, with pain ratings assessed after each scan. Generalized psychophysiological interaction analysis was used to compare the functional connectivity during painful stimulation to warmth stimulation. The following regions were used as seeds: primary visual, ventral visual, and bilateral dorsal visual networks. All regions were defined using the CONN toolbox.
Results
Overall, there was a significant reduction in pain intensity ratings in the placebo session compared to the baseline session (t(54)=3.27, p<.05, Cohen’s d=.44). Results revealed that increased FC between the medial visual network and bilateral insular cortex was negatively associated with percent pain reduction. Increased FC between the occipital visual network and the caudate was negatively associated with percent pain reduction. Lastly, increased FC between the bilateral lateral visual network and the middle frontal gyrus was positively associated with percent pain reduction.
Conclusions
Taken together, the results suggest all three visual network regions had significant changes in FC during painful stimulation that were associated with changes in reported pain intensity ratings. This provides further mechanistic evidence that visual network-related structures may be directly involved in acute pain processing and placebo analgesia. Future research should consider using visual network-related regions as a priori seeds to further characterize the relationship between occipital structures and pain processing.
References
Bush, N. J., Robinson, M., Bryan, M., Staud, R., & Boissoneault, J. (2021). Task-dependent functional connectivity of pain-related brain regions is related to magnitude of placebo analgesia. The Journal of Pain, 22(5), 603. https://doi.org/10.1016/j.jpain.2021.03.102
Bush, N. J., Schneider, V., Sevel, L., Bishop, M. D., & Boissoneault, J. (2021). Associations of Regional and Network Functional Connectivity With Exercise-Induced Low Back Pain. The Journal of Pain, 22(12), 1606–1616. https://doi.org/10.1016/j.jpain.2021.05.004
Kong, J., Loggia, M. L., Zyloney, C., Tu, P., LaViolette, P., & Gollub, R. L. (2010). Exploring the brain in pain: Activations, deactivations and their relation. Pain, 148(2), 257. https://doi.org/10.1016/j.pain.2009.11.008
Mayr, A., Jahn, P., Stankewitz, A., Deak, B., Winkler, A., Witkovsky, V., Eren, O., Straube, A., & Schulz, E. (2021). Patients with chronic pain exhibit individually unique cortical signatures of pain encoding. Human Brain Mapping, 43(5), 1676–1693. https://doi.org/10.1002/hbm.25750
Presenting Author
Nicholas J. Bush
Poster Authors
Nicholas Bush
PhD
University of Minnesota - Twin Cities
Lead Author
Topics
- Placebo