ReviewFunctional imaging of brain responses to pain. A review and meta-analysis (2000)Appréciation par l’imagerie fonctionnelle des réponses cérébrales à la douleur. Revue et méta-analyse.
Section snippets
CBF studies using PET
Even though the physiological significance of rCBF changes with regard to neural activity is not clearly established, there is considerable evidence that local CBF changes are generated by metabolic products of synaptic function, and therefore reflect variations in local synaptic activity 147, 148. The short scan duration (50–120 s) and inter-scan interval (10–15 min) permit multiple studies in rapid succession, therefore allowing comparisons between consecutive functional states, including the
Responses to acute pain in normal volunteers
Table I summarises the results of previously published PET studies in normal subjects. In a decreasing order of consistency, hemodynamic responses to acute pain in normal subjects have been observed in the following brain areas: insular and SII cortices (primarily contralateral to stimulation but also ipsilateral); anterior cingulate cortex (ACC, Brodmann areas [BA] 24 and 32); thalamus (primarily contralateral to stimulation but often bilateral); SI cortex contralateral to stimulation;
Spontaneous pain in patients with neuropathic pain
Spontaneous pain is difficult to investigate using functional imaging due to the need to compare in the same subjects a painful versus a pain-free condition. This binary situation is rare in clinical practice and the literature is therefore restricted to a few reports, in patients with either cancer pain alleviated by cordotomy [48], ongoing neuropathic pain alleviated by anaesthetic blocks [76], or central pain treated with motor cortex stimulation 67, 119. One common finding in these studies
Functional imaging and subcomponents of the pain experience
Imaging studies in recent years have allowed the visualisation of a number of brain regions which consistently respond to pain with changes in blood flow. These cortical targets appear to subserve different aspects of the multidimensional pain experience; thus, the sensory-discriminative aspects of pain perception appear to implicate the lateral thalamus, primary and second somatosensory regions and the insular cortex, while the additional activation of posterior parietal and prefrontal
Conclusion
This review has shown a good deal of convergent data and promising results that should, in the next years, improve our understanding of pain processing in the brain. In spite of the remaining discrepancies and interpretive difficulties, analysis of the literature shows an overall coherent picture of brain networks involved in pain processing, in fact much more coherent than what emerges from current meta-analyses in other fields of brain imaging [55]. We believe that pain imaging studies are
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