Effects of pain catastrophising on behavioural and cortical responses to pain-related stimuli

Pain catastrophising is an exaggerated negative mental set brought to bear during actual or anticipated pain experience (Sullivan et al., 2001b). People with high pain catastrophising were reported to perceive stronger pain intensity, attribute more pain to others, and solicit higher levels of social support from others when exposed to pain, relative to low pain catastrophisers (Sullivan et al., 2001b, Quartana et al., 2009). Three important models of pain catastrophising, the appraisal model, the attentional model, and the communal coping model, have been proposed to investigate the influence of pain catastrophising on pain-related outcomes. However, the neural basis of pain catastrophising in the social-emotional context among healthy people is poorly understood. This thesis utilised neuroimaging methods and novel experimental paradigms to explore effects of pain catastrophising on behavioural and cortical responses to pain-related stimuli in healthy people. It also investigates the associations between pain catastrophising and structural brain features. A comprehensive review of previous experimental findings was performed to identify novel research questions. Behavioural, eye movement, EEG and MRI data for 6 unique studies were collected. Chapter One features a review of relevant theories, studies, and findings pertaining to pain catastrophising. The specific research problems and hypotheses investigated in the thesis are explicitly described. Chapter Two describes the theory of the EEG, MRI and eye tracking methods used in the experimental chapters of the thesis. Chapter Three outlines the methods and materials used for each individual study. Chapter Four describes the experimental findings of the thesis. In the first study, a paradigm using a varying level of background noise was applied to evaluate the sensitivity to pain cues in high and low pain catastrophisers. No significant differences were found. In the second and third study, the eye tracking method and a dot-probe paradigm were used to measure the attentional processing to pain-related stimuli. High pain catastrophisers responded to probes after pain scenes slower compared to low pain catastrophisers. In the fourth study, ERP data revealed that high pain catastrophisers exhibited differences in ERP components and source activation patterns during the observation of pain pictures. The first four studies of this thesis reported that high pain catastrophisers attributed stronger pain to pain in others. In the fifth study, LEP data showed that high pain catastrophisers reduced perceived pain during viewing of comforting hand postures, and displayed enhanced ipsilateral operculo-insular activation to pictures not showing comforting gestures. In the final study of the thesis, a morphological analysis of cortical and subcortical structures was performed using high-resolution T1-weighted MR images. It demonstrated that alterations to the morphology of selected cortical regions and the dorsal striatum were associated with pain catastrophising. Chapter Five discusses the findings of each individual study in light of previous research and the implications and inferences that can be drawn from the data. Chapter Six represents a general discussion of the main findings of the thesis. This chapter examines how the findings of each individual study relate to the theories of pain catastrophising. The limitations of the thesis and the implications of the findings for future research are also discussed