Psychobiological mechanisms of impaired reward processing in chronic pain

点击翻译按钮获取中文摘要

Chronic pain is a major problem causing immense personal suffering and enormous socioeconomic costs. Although pain research has made great progress in the last decades, effective therapy options are still limited. This lack is probably caused by pain research largely focusing on molecular and neuronal mechanisms of nociception (i.e. the neural process of encoding of stimuli that damage or threaten to damage tissues), neglecting multifaceted experiences when being in pain. Recently, the potential etiological and pathogenetic role of emotional-motivational processing when being in pain, going beyond nociceptive processing, has been emphasized. A negative hedonic shift that is mirrored in a shift from nociceptive to emotional-motivational brain circuits has been described in chronic pain. Such a shift is assumed to cause rewarding stimuli as being perceived as less rewarding. However, the currently available data does not allow a conclusion on whether reward processing is truly altered in chronic pain patients and the psychobiological mechanisms of such a shift remain elusive. Providing a conceptual mechanism-oriented framework, the present project aims to characterize alterations in the processing of reward and corresponding neural correlates in patients with chronic pain. For this purpose, 50 patients with chronic back pain and 50 healthy controls will participate each in one functional magnetic resonance imaging (fMRI) and one laboratory session. In the fMRI session, motivation and hedonic experience and corresponding neural correlates related to monetary wins and losses as powerful secondary rewards and punishment and acute pain stimuli as a prototype of aversive stimuli and their avoidance as a rewarding event will be investigated as well as weighting of monetary rewards against avoidance of pain, when both are present concurrently. The laboratory session comprises an assessment of the motivation and hedonic experience of food-related stimuli as potent primary rewards at implicit and explicit levels and a comprehensive clinical assessment. Analysis of behavioral together with imaging data is aimed at testing specifically proposed alterations in brain circuits related to behavioral alterations to close a gap in the available literature. The chosen experimental paradigms allow a specific evaluation and differentiation of alterations in the processing of rewarding stimuli, which have been proposed as underlying the exacerbation of the chronification of pain, including affective comorbidities, thus being important from a theoretical, but also clinical perspective. Expected results will provide a necessary basis for future work, paving the way for exploiting mechanisms related to reward processing that are dysfunctional in chronic pain in mechanism-based interventions for the treatment of chronic pain.