NeuroImage
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Clinical Trial
Somatotopic organisation of the human insula to painful heat studied with high resolution functional imaging.
Pain perception is a multidimensional phenomenon, derived from sensory, affective, cognitive-evaluative and homeostatic information. Neuroimaging studies of pain perception have investigated the role of primary somatosensory cortex (SI); however, they have typically failed to demonstrate the expected somatotopy. An alternative network for the sensory component of pain has been proposed, involving a temperature and pain-specific nucleus of the thalamus (VMpo) and its projections to dorsal posterior insula (dpIns). ⋯ Single subject analysis demonstrated that only coordinates for dpIns activation were significantly dependent on stimulus location (Hotelling's Trace, P = 0.012). Coordinates for face (paired t test, P = 0.004) and hand (P < 0.001) activity were more lateral than those for foot, whilst face activation was anterior to the foot (P = 0.037). Based on single subject analyses, the average standard space (MNI) coordinates for face, hand and foot activity were (-40,-16,11), (-40,-19,14) and (-35,-21,11) respectively.
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The relationship between pain and cognitive function is of theoretical and clinical interest, exemplified by observations that attention-demanding activities reduce pain in chronically afflicted patients. Previous studies have concentrated on phasic pain, which bears little correspondence to clinical pain conditions. Indeed, phasic pain is often associated with differential or opposing effects to tonic pain in behavioral, lesion, and pharmacological studies. ⋯ This pain-related activity in medial prefrontal cortex and cerebellum was modulated by the demand level of the cognitive task. Our findings highlight a role for these structures in the integration of motivational and cognitive functions associated with a physiological state of injury. Within the limitations of an experimental model of pain, we suggest that the findings are relevant to understanding both the neurobiology and pathophysiology of chronic pain and its amelioration by cognitive strategies.