Investigating Perceptual Processing and Training in Fibromyalgia

Abstract

Fibromyalgia is a chronic pain condition associated with widespread pain, in addition to symptoms such as muscle stiffness and severe fatigue. Pain symptoms include the amplification of painful stimuli (hyperalgesia) and the perception of non-painful stimuli as painful (allodynia). Emerging evidence has suggested that disturbances in pain processing in fibromyalgia may be associated with altered bodily perception, including difficulties discriminating between incoming tactile stimuli (e.g. impairments in two-point discrimination ability). In line with this, the Bayesian Brain Model of chronic pain suggests that innocuous stimuli may result in painful experiences when an individual has difficulty discriminating the nature and intensity of incoming sensory information. Improving discrimination abilities through perceptual training paradigms may therefore have the potential to reduce pain in people with fibromyalgia, something that has been found to be effective in other chronic pain conditions. In addition to pain symptoms, recent research has found that people with fibromyalgia report increased unpleasantness of sensations in other modalities, including sounds and lights. This could suggest a global disturbance in sensory discrimination abilities in fibromyalgia, although few studies have addressed this directly. Such studies could have important implications for interventions where training discrimination performance in one modality could influence symptoms in another. The overall aims of this thesis were twofold. The first aim was to gain a greater understanding of how perception is affected across sensory modalities in fibromyalgia. The second aim was to develop a perceptual training protocol targeted towards people with fibromyalgia. Study one explored self-reported measures of intolerance (unpleasantness) and subjective perceptual ability (discrimination abilities) across sensory modalities in fibromyalgia. In line with previous findings, people with fibromyalgia reported increased intolerance across sensory modalities. Contrary to expectation, however, people with fibromyalgia also reported enhanced subjective perceptual ability for the majority of sensory modalities. Exploratory cluster analyses highlighted three main fibromyalgia subgroups who significantly differed in their sensory features, highlighting the heterogeneity of people with the condition. Using psychophysical methods, study two measured intensity discrimination thresholds for tactile, auditory and painful stimuli to provide a more objective measure of perceptual ability across modalities in fibromyalgia. Although this study had limited statistical power and a floor effect for the tactile modality, a trend was found towards smaller discrimination thresholds across the auditory and pain modalities in fibromyalgia indicative of enhanced perception, seemingly at odds with previous findings. These discrepancies could also be explained by the potential heterogeneity of the condition. To address the second aim, study three involved testing proof of concept of an intensity discrimination training paradigm in a pain-free sample. Study four involved investigating the feasibility and acceptability of a three-week homebased auditory perceptual training protocol in people with fibromyalgia. In both training studies, training consisted of trial-by-trial feedback where participants were asked to make judgements about which of two stimuli was most intense. In study three participants' intensity discrimination performance got significantly worse after training which was attributed to boredom and limited room for improvement. In study four, the training protocol was found to be acceptable and feasible, suggesting promise for the use of an at home training protocol using auditory stimuli for people with fibromyalgia. Taken together, these studies suggest that fibromyalgia is a heterogenous condition in terms of perceptual processing and that training paradigms may be suitable for only a subset of people with fibromyalgia.

Date of Award	7 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Richard Brown (Main Supervisor) & Ellen Poliakoff (Co Supervisor)