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Towards a neurocognitive model of pain-related fear

Book - Dissertation

Contemporary biopsychosocial models of chronic pain, such as the fear-avoidance model (Vlaeyen et al., 2016; Vlaeyen and Linton, 2012, 2000), posit that pain-related fear plays a pivotal role in the development and maintenance of the disability experienced by patients. Yet, as discussed in Chapter 1, our knowledge of the neuro-cognitive mechanisms underlying pain-related fear is limited. This led us to develop an experimental paradigm that mimicked the pain-related fear individuals with chronic pain may experience as a consequence of stimulus-evoked pain (e.g., allodynia; perceiving non-painful touch as painful) or as a consequence of stimulus-independent pain (e.g., spontaneous pain fluctuations). We developed a classical cued and contextual fear conditioning paradigm that employed innocuous vibrotactile stimulation of the fingers as conditioned stimuli (CSs) and painful electrocutaneous stimulation of the ipsilateral wrist as an unconditioned stimulus (US). With this paradigm and meta-analytic methods, we addressed the following research questions: 1) do participants acquire (Chapter 2), generalize (Chapter 3), and extinguish (Chapter 2) conditioned fear responses to touch when associated with pain? 2) Are the neural correlates of pain-related fear comparable to the neural correlates of other conditioned fears (using merely aversive, non-painful stimuli as USs) (Chapter 4)? 3) What are the neural networks related to fear of touch (Chapter 5)?We found that participants successfully acquired and extinguished both cued and contextual fear of touch (Chapter 2). However, we did not find evidence of fear generalization to novel touch (Chapter 3). From these results we conclude that pain-related fear responses to innocuous touch can develop and reduce in a manner consistent with contemporary associative learning theories, although the spreading of fear of touch requires further investigation. We found that the neural network relating to the acquisition of cued fear of touch included regions involved in emotional learning processes (putamen, angular gyrus, anterior insula, and ventromedial prefrontal cortex/vmPFC), motor regions (primary motor cortex/MI and supplementary motor area/SMA), and somatosensory regions (primary and secondary somatosensory cortices/SI and SII). The neural correlates of contextual fear of touch were limited to the bilateral caudate nuclei (Chapter 5). These results, combined with our finding that the primary somatosensory cortex (SI) is differentially recruited for pain-related fear compared to other conditioned fears (Chapter 4), points to a crucial role for somatosensory processing in the experience of pain-related fear. In Chapter 6, we discuss the potential implications of these findings, and directions for future research that could build on this work
Publication year:2021