Abstract
Two parallel di-synaptic routes convey nociceptive input to the telencephalon: the spino-thalamic system projecting principally to the posterior insula, and the spino-parabrachial pathway reaching the amygdalar nucleus. Interplay between the two systems underlies the sensory and emotional aspects of pain, and was explored here in humans with simultaneous recordings from the amygdala, posterior and anterior insulae. Onsets of thermo-nociceptive responses were virtually identical in the posterior insula and the amygdalar complex, but no significant functional connectivity was detected between them using coherence analysis. Anterior insular sectors responded with ~30 ms delay relative to both the posterior insula and the amygdala. While intra-insular functional correlation was significant during the whole analysis period, coherence between the anterior insula and the amygdala became significant after 700 ms of processing. Phase lags indicated information transfer initially directed from the amygdalar complex to the insula. Parallel but independent activation of sensory and limbic nociceptive networks appear to converge in the anterior insula in less than one second. While the anterior insula is often considered as providing input into the limbic system, our results underscore its reverse role, i.e., receiving and integrating very rapidly limbic with sensory input, to initiate a perceptual decision on the stimulus ‘painfulness’.
Highlights
Pain is a complex experience involving sensory, cognitive and motivational components
We tested the above hypothesis by analysing nociceptive-specific evoked potentials and functional connectivity in 10 epileptic patients with electrodes simultaneously implanted in the posterior and anterior insular sectors, as well as in the amygdalar nucleus
The results suggest that, during the first second that follows a noxious stimulus, an initial parallel and uncorrelated nociceptive processing in sensory and limbic systems is rapidly followed by a functional convergence of both toward the anterior insula
Summary
Pain is a complex experience involving sensory, cognitive and motivational components Such diversity is supported by a variety of ascending systems conveying nociceptive information from the spinal cord to the telencephalon, of which the two main disynaptic routes are the spino-thalamo-cortical (STC) and the spino-parabrachial-amygdalar pathways. We tested the above hypothesis by analysing nociceptive-specific evoked potentials and functional connectivity in 10 epileptic patients with electrodes simultaneously implanted in the posterior and anterior insular sectors, as well as in the amygdalar nucleus Such exceptional access to responses in the three regions allowed analysing both response timing and functional inter-areal relationships via phase-coherence, and generated a comprehensive image of the activities of the three structures. The results suggest that, during the first second that follows a noxious stimulus, an initial parallel and uncorrelated nociceptive processing in sensory and limbic systems is rapidly followed by a functional convergence of both toward the anterior insula
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
