Cognitive neuroscience investigations of the role of the somatosensory system in health and disease

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There has been a recent surge in the number of studies using functional magnetic resonance imaging (fMRI) to investigate the cortical and subcortical processing of somatosensation (including, touch, pain and thermosensation) in the human brain. These studies have benefited from the advent of vibrotactile and thermal stimulus delivery systems able to work within MR environments but with precise (electrically-driven) stimulus control capabilities. The proposed research will make use of such devices to investigate the neurophysiological and neuropsychological basis of tactile and nociceptive processing in both healthy controls and patients with somatic disorders. Specifically, in collaboration with expert colleagues in the fields of tactile attention, clinical somatoform disorder and clinical pain we aim to develop a programme of research investigating how the tactile and nociceptive systems function normally when attending and responding to stimulation of the body: using both behavioural measures of performance and neuroimaging measures of brain activity. We will begin by investigating the neurophysiological and neuropsychological interaction between touch and pain within the human brain, with a particular focus on the parietal lobes (anterior and posterior). Previous functional imaging studies have positied a role for the parietal lobes in the human perception of pain but acknowledge the functional heterogeneity of this area. For example, re-organisation within primary somatosensory cortex is believed to contribute to Phantom Limb Pain, whilst disruption of sensory input from the thalamus to the parietal opercular region (either through lesion or tumour compression) causes severe pain in extremities (so called `Central Pain¿ or `Post-Stroke Pain¿) and loss of normal tactile sensation. Similarly, area 7b in the posterior parietal cortex has been implicated not only in the ability to perceive pain, but also in the ability to attend to a painful stimulus on the body, to predict the sensory consequences of an upcoming painful event and the multisensory representation of pain. Our aim is to investigate whether the attentional modulation of pain and touch is disrupted in patients with somatic disorders (for which an adequate organic explanation for the symptoms cannot be found) as we suggest that abnormal inhibitory attentional mechanisms (through the parietal lobes and their outputs to the prefrontal and anterior cingulated cortices) may be responsible for conditions such as non-specific low back pain and medically unexplained symptoms.