The nociceptive system, from which pain emerges as a percept, may be viewed as a dual afferent sensory network whose peripheral inputs are conveyed by Ad- and C-fibres.
Human electrophysiological studies, using event-related brain potentials (ERP), as well as human neuroimaging studies, using functional magnetic resonance imaging (fMRI) and positron-emitting tomography, have shown that a nociceptive event elicits brain responses within an extensive cortical network, bilaterally involving secondary somatosensory, insular, and anterior cingulate cortices.
The respective involvement of these cortical responses to the perception of pain is quite largely unknown. A number of studies have pointed at the similarities between nociceptive evoked potentials and late evoked potentials, which may be elicited by a sensory stimulus regardless of its modality.
Determining whether all or part of the ERP and fMRI activity elicited by a nociceptive stimulus reflects brain processes truly specific of the nociceptive system constitutes the first objective of this research project.
Human electrophysiological studies have shown the existence of significant interactions between the central processing of Ad- and C-fibre nociceptive input but also between the central processing of nociceptive and non-nociceptive somatosensory input. Indeed, reproducible C-fibre ERPs appear to be recorded only if concurrent activation of Ad-nociceptors is avoided.
Similarly, reproducible Ad-fibre ERPs appear to be recorded only if concurrent activation o f non-nociceptive Aß-fibres is avoided. Better understanding the mechanisms which condition the triggering of nociception-related ERP and fMRI activity constitutes the second objective of the project.
By providing some insight as to the functional significance of ERP and fMRI correlates of nociception-related brain processes, this proposal may contribute to the development of novel diagnostic tools and therapeutic strategies for the treatment of pain.
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