Pain
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Chronic pain is a highly prevalent and severely disabling disease that is associated with substantial changes of brain function. Such changes have mostly been observed when analyzing static measures of resting-state brain activity. However, brain activity varies over time, and it is increasingly recognized that the temporal dynamics of brain activity provide behaviorally relevant information in different neuropsychiatric disorders. ⋯ As microstate D has previously been related to attentional networks and functions, these abnormalities might relate to dysfunctional attentional processes in chronic pain. Subgroup analyses replicated microstate D changes in patients with chronic back pain, while patients with chronic widespread pain did not show microstates alterations. Together, these findings add to the understanding of the pathophysiology of chronic pain and point to changes of brain dynamics specific to certain types of chronic pain.
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Accumulating evidence suggests hippocampal impairment under the chronic pain phenotype. However, it is unknown whether neuropathic behaviors are related to dysfunction of the hippocampal circuitry. Here, we enhanced hippocampal activity by pharmacological, optogenetic, and chemogenetic techniques to determine hippocampal influence on neuropathic pain behaviors. ⋯ Altogether, these results imply that downregulation of the DH circuitry during chronic neuropathic pain aggravates pain-related behaviors. Conversely, activation of the DH reverses pain-related behaviors through local excitatory and opioidergic mechanisms affecting DH functional connectivity. Thus, this study exhibits a novel causal role for the DH but not the VH in controlling neuropathic pain-related behaviors.
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Meta Analysis
Effectiveness of placebo interventions for patients with non-specific low back pain: a systematic review.
Little is known about the effectiveness of placebo interventions in patients with nonspecific low back pain (LBP). This systematic review assessed the magnitude of the effects of placebo interventions as compared to no intervention in randomized controlled trials (RCTs) including patients with LBP. Embase, MEDLINE (Ovid), and Cochrane CENTRAL databases were searched from inception to December 5, 2019. ⋯ These results show placebo interventions are more effective than no intervention at short-term follow-up in patients with chronic LBP. However, the magnitude of the effects is probably not clinically relevant (approximately 8 points on a 0-100 pain scale). Future research should identify effect modifiers and causal mechanisms explaining the short-term effects of placebo interventions in patients with chronic LBP.