COVID-19 Journal Club
The COVID-19 Global Pandemic has posed significant challenges to the pain community. To reinforce the message that the we—those who do human pain research—are part of a community, I put together the COVID-19 Journal Club (or as some like to call it, the #PainStars Forum). It's an opportunity to connect, to remain intellectually stimulated, to learn, and to keep up with the literature.
We meet over Zoom every month. The specifics, papers, and link to the Zoom will be posted here. We look forward to seeing you all.
Wednesday, January 27, 2021, 1 pm EST
Title: Sex differences in brain modular organization in chronic pain
Presented by: Dr. Camille Fauchon, Postdoctoral Fellow (PI: Karen Davis), Krembil Brain Institute, University Health Network, Canada
Abstract: Men and women can exhibit different pain sensitivities and many chronic pain conditions are more prevalent in one sex. Although there is evidence of sex differences in the brain, it is not known whether there are sex differences in the organization of large-scale functional brain networks in chronic pain. Here, we used graph theory with modular analysis and machine-learning of resting-state (RS)-fMRI data from 220 participants; 155 healthy controls and 65 individuals with chronic low back pain due to ankylosing spondylitis (AS), a form of arthritis.We found an extensive overlap in the graph partitions with the major brain intrinsic systems (i.e., default mode, central, visual and sensorimotor modules), but also sex-specific network topological characteristics in healthy people and those with chronic pain. People with chronic pain exhibited higher cross-network connectivity, and sex-specific nodal graph properties changes (i.e., Hubs disruption), some of which were associated with the severity of the chronic pain condition. Females exhibited atypically higher functional segregation in the mid- and subgenual cingulate cortex and lower connectivity in the network with the default mode and fronto-parietal modules; whereas males exhibited stronger connectivity with the sensorimotor module. Classification models on nodal graph metrics could classify an individuals' sex and whether they have chronic pain with high accuracies (77-92%). These findings highlight the organizational abnormalities of RS-brain networks in people with chronic pain and provide a framework to consider sex-specific pain therapeutics.
Relevant Paper: https://pubmed.ncbi.nlm.nih.gov/33044396/
Meeting ID: 842 4763 0994
Wednesday, February 17, 2021, 3 pm EST
Title: Chronic pain precedes disrupted eating behavior in back pain patients
Presented by: Dr. Paul Geha, Assistant Professor, University of Rochester, USA
Abstract: Chronic low-back pain (CLBP) and obesity are interrelated, but the mechanisms of this interaction are still poorly understood. We have previously shown that patients with CLBP exhibit blunted hedonic response to highly palatable fat-rich food and disrupted satiety signals. This observation is consistent with the reorganization of the nucleus accumbens observed in CLBP patients, and the role of this striatal area in the hedonic perception of highly palatable foods. Here we asked how eating behavior would be affected in back pain patients before and after they transition to chronic pain or recover from it, and how does hedonic perception of fat-rich food relate to the properties of the nucleus accumbens in this patients’ population. Therefore, we tested sub-acute back pain patients and healthy controls at baseline when back pain was 6-12 weeks old, and at approximately one-year follow-up using behavioral assays and structural brain imaging. Likewise, we tested a cohort of CLBP patients at one time point. CLBP patients and, surprisingly, sub-acute back pain patients who recovered at follow-up (SBPr) showed disrupted eating behavior while sub-acute back pain patients who persisted in having pain at follow-up (SBPp) had an intact eating behavior. However, only SBPp patients at baseline and follow-up, and CLBP patients, showed a direct relationship between hedonic perception of fat-rich food and nucleus accumbens volume. Our data reproduces our previous findings and suggest that disrupted eating behavior sets in after pain chronification and is directly related to the properties of nucleus accumbens.
Meeting ID: 834 7571 0509
Wednesday, March 3, 2021, 1 pm EST
Title: Confidence in subjective pain is predicted by reaction time during decision making
Presented by: Troy Dildine, PhD Candidate (Atlas Lab), NCCIH/NIH and Karolinska Institute
Abstract: Self-report is the gold standard for measuring pain. However, decisions about pain can vary substantially within and between individuals. We measured whether self-reported pain is accompanied by metacognition and variations in confidence, similar to perceptual decision-making in other modalities. Eighty healthy volunteers underwent acute thermal pain and provided pain ratings followed by confidence judgments on continuous visual analogue scales. We investigated whether eye fixations and reaction time during pain rating might serve as implicit markers of confidence. Confidence varied across trials and increased confidence was associated with faster pain rating reaction times. The association between confidence and fixations varied across individuals as a function of the reliability of individuals’ association between temperature and pain. Taken together, this work indicates that individuals can provide metacognitive judgments of pain and extends research on confidence in perceptual decision-making to pain.
Relevant Paper: https://www.nature.com/articles/s41598-020-77864-8
Meeting ID: 868 4882 1728
Tuesday, March 30, 2021, 1 pm EST
Title: Forced choices reveal a trade-off between cognitive effort and physical pain
Presented by: Todd Vogel, PhD Candidate (PI: Dr. Mathieu Roy), Department of Psychology, McGill University, Montréal, Canada
Abstract: Cognitive effort is described as aversive, and people will generally avoid it when possible. This aversion to effort is believed to arise from a cost–benefit analysis of the actions available. The comparison of cognitive effort against other primary aversive experiences, however, remains relatively unexplored. Here, we offered participants choices between performing a cognitively demanding task or experiencing thermal pain. We found that cognitive effort can be traded off for physical pain and that people generally avoid exerting high levels of cognitive effort. We also used computational modelling to examine the aversive subjective value of effort and its effects on response behaviours. Applying this model to decision times revealed asymmetric effects of effort and pain, suggesting that cognitive effort may not share the same basic influences on avoidance behaviour as more primary aversive stimuli such as physical pain.
Meeting ID: 853 3610 9070
Tuesday, April 20, 2021, 3 pm EST
Title: A picture is worth a thousand words: linking fibromyalgia pain widespreadness from digital pain drawings with pain catastrophizing and brain cross-network connectivity
Presented by: Dr. Vitaly Napadow, Associate Professor in Radiology, Harvard Medical School, USA
Abstract: Pain catastrophizing is prominent in chronic pain conditions such as fibromyalgia, and has been proposed to contribute to the development of pain widespreadness. However, the brain mechanisms responsible for this association are unknown. We hypothesized that increased resting Salience Network (SLN) connectivity to nodes of the Default Mode Network (DMN), representing previously reported pain-linked cross-network enmeshment, would be associated with increased pain catastrophizing and widespreadness across body sites.We applied functional Magnetic Resonance Imaging (fMRI) and digital pain drawings (free-hand drawing over a body outline, analyzed using conventional software for multivoxel fMRI analysis) to investigate precisely-quantified measures of pain widespreadness and the associations between pain catastrophizing (Pain Catastrophizing Scale, PCS), resting brain network connectivity (Dual-regression Independent Component Analysis, 6-minute multiband accelerated fMRI), and pain widespreadness in fibromyalgia patients (N=79).Fibromyalgia patients reported pain in multiple body areas (most frequently the spinal region, from the lower back to the neck), with moderately high pain widespreadness (mean±SD: 26.1±24.1 percent of total body area), and high PCS scores (27.0±21.9, scale range: 0-52), which were positively correlated (r=0.26,p=0.02). A whole-brain regression analysis focused on SLN connectivity indicated that pain widespreadness was also positively associated with SLN connectivity to the Posterior Cingulate Cortex (PCC), a key node of the DMN. Moreover, we found that SLN-PCC connectivity statistically mediated the association between pain catastrophizing and pain widespreadness (p=0.01).In conclusion, we identified a putative brain mechanism underpinning the association between greater pain catastrophizing and a larger spatial extent of body pain in fibromyalgia, implicating a role for brain SLN-DMN cross-network enmeshment in mediating this association.
Relevant Paper: https://pubmed.ncbi.nlm.nih.gov/33230008/
Meeting ID: 817 7935 5356