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Title: Attentional modulations of pain perception: evidence from laser evoked potentials
Tutor: Giandomenico, Iannetti
Keywords: nociception
event related potentials
laser evoked potentials
Issue Date: 15-Jan-2010
Abstract: This thesis aims to provide a contribution to the current neurophysiological and psychophysiological understanding of nociception and pain processing in humans. The introduction of high-power, radiant heat stimulators (lasers) in sensory physiology has revolutionised the study of the nociceptive system. Laser pulses activate Aδ and/or C skin nociceptors selectively, i.e. without coactivating deeper, tactile mechanoreceptors, and elicit brain responses that can be detected using electroencephalography, and are called laser-evoked potentials (LEP). This was the technique applied in the two experimental studies reported in the present thesis work. The doctoral dissertation is organized in five chapters. Chapter 1 – Introduction - defines the concepts of nociception and pain. It also provides an introduction to the event related potential technique (ERP), a description of basic biophysics and neurophysiology related to LEP recording, followed by a literature review of its related cortical generators. In addition, the Chapter attempts to draw an elementary parallel between LEPs and other EPs elicited by stimuli belonging to other sensory modalities. Chapter 2 – Determinants of vertex potentials – describes the determinants of neural processes of pain perception and support their interpretation through a neurocognitive model of attention. The mechanism of attention allows allocating resources for selection and integration of this process with working memory requirements. More in detail, cognitive science suggested that the attention mechanism can be divided into two categories: stimulus-driven (or ‘bottom-up’) and goal-directed (or ‘top-down’). ‘Top-down’ and ‘bottom-up’ are treated as key interpretative categories to explain the findings reported in this thesis. Infact, they are metaphors which are used to represent information processing in a hierarchical fashion, where lower levels of processing would rely on the physical features of the stimulus while higher levels would involve comparisons with information stored in memory, selection of relevant information in competition and response to the stimulus. A review of selected literature in the field or ERP studies of sensory processing is provided and interpreted within this framework. The thesis aims to contribute to the understanding of both ‘bottom-up’ and ‘top-down’ mechanisms of attention during nociceptive processing, with two distinct experiments. Chapter 3 – Contribution to the analysis of ‘bottom-up features: “Dishabituation of laser-evoked EEG responses: dissecting the effect of certain and uncertain changes in stimulus modality” - presents a study where the hypothesis that a change of modality (from auditory to nociceptive and vicerversa, rather than no change at all) can significantly modulate brain responses (no matter the subjects expectation of this change) has been tested. The results of this study bring support for a determinant role of saliency (here modulated by the novelty introduced by a change in the stimulus modality) in affecting brain responses to the sensory input. Chapter 4 - Hypnotic modulation of sensory and affective dimensions of pain: a top-down signature on pain experience - introduces a study where hypnotic suggestions were used to draw subject’s attention either on intensity or on unpleasantness of pain perception. Thus, the study aimed to investigate whether this manipulation could induce a dissociation between this two measure of subjective experience and whether LEP could reflect the role of focused attention and expectation in indexing changes of subjective feeling. The results are discussed according to previous literature and to a neurocognitive model of pain processing as observed during an altered state of consciousness known to heighten the fronto-parietal network of sustained attention. In Chapter 5 - General discussion - the findings related to these two different research lines are integrated and discussed considering the existing theoretical accounts. The critical assumption is that the understanding of pain processing would largely benefit from the application of an attention-driven interpretative framework within which can be included different theoretical-epistemological views concerning (II) the Bayesian inference in perception, (III) the motivational account of pain monitoring and control, (IV) the neuroanatomy of homeostatic feeling of body integrity and self-regulation. As conclusive remark, the work presented in this thesis wish to highlight the importance of a renewed concept of ‘pain matrix’, based on its function of potential threat detector and action planner, in order to preserve the integrity of the body. In addition, the interpretation of pain as homeostatic-motivational force naturally carries us to consider the ‘pain matrix’ not as a sensory-specific cortical network but rather as an action-specific network, representing the activity by which the individual identifies and responds purposefully to a sudden, potential threat inside or outside of the body.
Research interests: - Neurophysiology and Psychophysiology of sensory representation; - Neurophysiology and Psychophysiology of pain perception; - Psychophysiology of pain observation and empathy for other's pain; - EEG, ERP, LEP, TMS techniques; - Psychology and Neuroscience of placebo/nocebo phenomena, hypnosis and suggestibility; - Psychology and Neuroscience of emotion and attention; - Bioelectromagnetism and biological effects of electromagnetic fields
Personal skills keywords: Develop and maintain multiple projects and collaborations
Show initiative, work independently and be self-reliant
Self-discipline, motivation and thoroughness
Keeping abreast of current developments/future trends in the research domain
Effectively implement research methodology and data analysis

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