NOCICEPTIVE PREDICTIVE PROCESSING AND ALLOSTATIC LOAD IN FIBROMYALGIA

Summary

Fibromyalgia syndrome is a severe chronic pain disorder of unknown origin. It leads to considerable psychological stress and severe limitations in quality of life, morbidity and even mortality. With an estimated prevalence of 2-5% in the general population, fibromyalgia syndrome is common and therefore has immense socio-economic relevance. For patients with fibromyalgia syndrome, therapy is difficult, treatment results are usually unsatisfactory, and the pathogenesis is still largely unknown. A disturbance of central nervous pain processing is assumed which leads to sensory hypersensitivity to pain with allodynia, i.e. the perception of benign, non-harmful stimuli is experienced as painful. Allodynia is a potential indicator of abnormal processing of sensory stimuli and can be seen as false perception or misinterpretation of threat signals.

In this study we will investigate whether computational modeling of central nervous system predictive processing of sensory information can explain the dysfunctional pain perception in fibromyalgia. Using a Pavlovian learning task, we aim to induce conditioned pain perceptions in patients with fibromyalgia syndrome and pain-free controls. Using a hierarchical probabilistic Gaussian filter model, we will analyze the different levels of the latent computational processes underlying the conditioned false-positive perceptions of pain in the response model of the participants. We will then use computational modeling of somatosensory perception to investigate whether fibromyalgia patients are more susceptible to conditioned sensory perceptions than pain-free controls when giving up conditioned perception, and whether this is related to the specific weighting of expectation states against sensory information. Similarly, computational modeling will be used to capture perceptual beliefs about stimulus contingency and the volatility of that contingency. Formally, we assume that fibromyalgia patients have a stronger weighting of previous expectation states compared to normal controls, while at the same time the false-positive rates in our conditioned perceptual paradigm increase. The sensory test paradigm developed in this study should make it possible to quantify the specific weighting of expected states versus sensory information in chronic pain disorders in the future and to identify novel biomarkers of pain chronification.