Nociception | EPFL Graph Search

vignette|Fibres nerveuses sensorielles stimulées au-delà de l'intensité nocive provoquant une douleur nociceptive. La nociception est une fonction défensive présente chez les vertébrés ainsi que chez les invertébrés. C'est une fonction permettant l'intégration, au niveau du système nerveux central, d'un stimulus potentiellement nocif via l'activation des nocicepteurs cutanés, viscéraux, musculaires et articulaires. Le transport de l'information sensorielle par les nerfs se fait de la périphérie (lieu de transduction d'un message potentiellement nocif en nociception) jusqu'au thalamus. La nociception est souvent décrite comme transmettant les messages "douloureux", cependant cette conception est erronée. En effet la nociception et la douleur sont deux choses différentes . Il existe un grand corpus de preuve dissociant la nociception de la douleur, montrant qu'il n'existe pas de lien de causalité entre le premier et le second . V

Seeing and identifying with a virtual body decreases pain perception

Olaf Blanke, Bigna Lenggenhager, Roland von Känel

Pain and the conscious mind (or the self) are experienced in our body. Both are intimately linked to the subjective quality of conscious experience. Here, we used virtual reality technology and visuo-tactile conflicts in healthy subjects to test whether experimentally induced changes of bodily self-consciousness (self-location; self-identification) lead to changes in pain perception. We found that visuo-tactile stroking of a virtual body but not of a control object led to increased pressure pain thresholds and self-location. This increase was not modulated by the synchrony of stroking as predicted based on earlier work. This differed for self-identification where we found as predicted that synchrony of stroking increased self-identification with the virtual body (but not a control object), and positively correlated with an increase in pain thresholds. We discuss the functional mechanisms of self-identification, self-location, and the visual perception of human bodies with respect to pain perception.

2011

An insular cortex - lateral amygdala network in fear learning

Shriya Palchaudhuri

Animals are capable of evaluating sensory cues for possible threats and adapting their behaviours accordingly. Fear learning is an evolutionarily conserved behaviour crucial for animal survival, during which sensory percepts with a negative reinforcing quality, also called unconditioned stimuli (US), influence the valence of initially neutral sensory cues (conditioned stimulus, CS). The lateral amygdala (LA) is thought to integrate information about sensory cues like tones (the CS), and information about primary reinforcers like painful stimuli (the US). Nevertheless, synaptic afferents to the LA and upstream brain areas remain understudied in fear learning. The posterior insular cortex (pInsCx) has been shown to project to the LA and is known to be a multimodal sensory area which processes auditory, somatosensory-nociceptive, and interoceptive information, making it an interesting brain area with a putative role in fear learning. My PhD thesis therefore aimed to investigate a possible connection from the pInsCx to the LA, and the role of this pathway in the fear learning circuitry. I first used anatomical anterograde and retrograde tracing strategies in the mouse to study the afferents to the LA. Besides previously known inputs, I found that the granular (GI) and the dysgranular (DI) areas of the pInsCx strongly project to the anterior LA. With optogenetically-assisted circuit mapping (OACM), I found a glutamatergic monosynaptic connection from the pInsCx to LA principal neurons that, in agreement with the anatomical findings, was localized more to the anterior LA. In comparison, a well-studied auditory thalamic (MGm/PIN) input was localized more to the posterior LA. Despite this regional input specificity, ~30% LA principal neurons received projections from both areas. Thus, in the first part, using anatomical tracing and OACM, I have unambiguously shown a robust functional excitatory connection from the pInsCx (GI/DI) to the LA.In the second part of my thesis, I aimed to characterize the role of the pInsCx and the pInsCx-LA pathway in fear learning. Using archaerhodopsin-mediated optogenetic inhibition, I found that silencing of footshock-driven activity of pInsCx neurons in-vivo, partially blocks auditory-cued fear memory. These results were also supported by chemogenetic silencing of the pInsCx during the training day, which led to a modest impairment of fear retrieval a day later. Next, to investigate the role of the pInsCx-LA projection more specifically, I used a retrograde expression approach to silence LA-projectors during the footshock, which again, suppressed fear memory one day later. In further ex-vivo experiments, I found that EPSCs at the pInsCx-LA connection exhibited an increased AMPA/NMDA ratio following fear learning, indicating that plasticity occurs at this pathway during fear learning. Finally, miniature microscopic Ca2+ imaging of LA neurons combined with halorhodopsin-mediated axon inhibition, showed that the pInsCx-LA excitatory synapse contributes to transmitting footshock information to a sub-population of LA neurons. This study unravels the relationship between two serial nodes, the pInsCx and the LA, in the fear learning network. Thus, the pInsCx-LA connection is a novel pathway in auditory-cued fear memory that is strengthened with learning and that partly provides aversive information to the amygdala.

EPFL2022

An insular cortex - lateral amygdala network in fear learning

Shriya Palchaudhuri

EPFL2022