The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Luis Garcialarrea - One of the best experts on this subject based on the ideXlab platform.
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Insular limbic dissociation to intra epidermal electrical aδ activation a comparative study with thermo nociceptive laser stimulation
European Journal of Neuroscience, 2018Co-Authors: Maud Frot, Hélène Bastuji, Caroline Perchet, Koichi Hagiwara, Luis GarcialarreaAbstract:: Intra-epidermal electrical stimulation (IEES) has been shown to activate selectively Aδ fibers subserving spinothalamic-mediated sensations. Owing to electrically induced highly synchronous afferent volleys, IEES induces Aδ-mediated evoked potentials at nonpainful intensities, contrasting with thermo-nociceptive laser pulses which entail painful pricking sensations. Here, we recorded intracortical responses from sensory and limbic-cognitive regions of human subjects in response to IEE and laser stimuli, in order to test the hypothesis that IEES could dissociate the sensory from nonsensory networks of nociceptive processing. Intracortical evoked potentials were obtained in 11 epileptic patients with stereotactically implanted electrodes in sensory regions receiving spinothalamic afferents (Posterior Insula), limbic regions receiving spino-parabrachial input (amygdalar nucleus), and high-order affective-cognitive regions (anteromedial frontal cortex, including perigenual anterior cingulate and rostromedial prefrontal areas). Responses in the sensory Posterior Insula were of similar amplitude and latency to IEE and laser stimuli (after accounting for heat-transduction time of laser), and consistent in both cases with spinothalamic activation. However, responses to IEES in the amygdala and the anteromedial frontal regions were inconsistent and significantly smaller compared to those evoked to the laser stimulation. Thus, IEES can effectively activate the spinothalamic-sensory system with little recruitment of affective-motivational networks, including those triggered by spino-parabrachio-amygdalar projections. The fact that identical sensory responses were associated to either painful or nonpainful percepts underscores that subjective pain perception is not solely dependent on the sensory recruitment, but rather on the combined activation of sensory, limbic and cognitive areas with precise spatiotemporal relations.
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pain syndromes and the parietal lobe
Handbook of Clinical Neurology, 2018Co-Authors: Luis Garcialarrea, François MauguièreAbstract:Pain was considered to be integrated subcortically during most of the 20th century, and it was not until 1956 that focal injury to the parietal opercular-Insular cortex was shown to produce selective loss of pain senses. The parietal operculum and adjacent Posterior Insula are the main recipients of spinothalamic afferents in primates. The innermost operculum appears functionally associated with the Posterior Insula and can be segregated histologically, somatotopically and neurochemically from the more lateral S2 areas. The Posterior Insula and Medial Operculum (PIMO) encompass functional networks essential to initiate cortical nociceptive processing. Destruction of this region selectively abates pain sensations; direct stimulation generates acute pain, and epileptic foci trigger painful seizures. Lesions of the PIMO have also high potential to develop central pain with dissociated loss of pain and temperature. The PIMO region behaves as a somatosensory area on its own, which handles phylogenetically old somesthetic capabilities based on thinly myelinated or unmyelinated inputs. It integrates spinothalamic-driven information - not only nociceptive but also innocuous heat and cold, crude touch, itch, and possibly viscero-somatic interoception. Conversely, proprioception, graphesthesia or stereognosis are not processed in this area but in S1 cortices. Given its anatomo-functional properties, thalamic connections, and tight relations with limbic and multisensory cortices, the region comprising the inner parietal operculum and Posterior Insula appears to contain a third somatosensory cortex contributing to the spinothalamic attributes of the final perceptual experience.
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o1 comparison between intra epidermal electrical and laser stimulations an intracranial evoked potential study
Clinical Neurophysiology, 2017Co-Authors: Koichi Hagiwara, Maud Frot, Hélène Bastuji, Caroline Perchet, Luis GarcialarreaAbstract:Objectives Intra-epidermal electrical stimulation (IES) is considered to stimulate selectively and directly A δ fibres, by-passing the heat-mediated receptor process of laser stimulation. However, there has been only extra-cranial data to argue such fiber selectivity. Here, we recorded intracranial responses to IE and laser stimulations, to assess whether the two types of stimulation can demonstrate identical responses in precisely-localized brain regions. Methods We analysed intracranial evoked potentials to IE and laser (Nd:YAP) stimulations in 11 epileptic patients with stereotactically-implanted electrodes in the spinothalamic-receiving Posterior Insula (12 contacts) and affective-cognitive regions (amygdala, 8 contacts; anteromedial frontal region, 13 contacts). Results While both IE and laser stimuli were perceived as ‘pricking’ sensations, those elicited by IES were of lesser intensity and intrusiveness. In the Posterior Insula, IES-evoked and laser-evoked potentials were similar in waveform and amplitude. Peak-latencies were significantly shorter for IES than for laser, the mean latency difference being of 15.8 ms. In both the amygdala and anteromedial frontal regions, amplitudes were significantly attenuated for IES, as compared to laser. Discussion The latency difference in the Posterior Insula was concordant with the heat-transduction time of laser, suggesting the ability of IES to activate selectively the spinothalamic system. The depressed activations in the amygdala and anteromedial frontal regions, while preserved in the Posterior sensory Insula, were compatible with modest attentional-affective drive for IES. Conclusions IES can effectively activate the A δ -mediated sensory-encoding system (Posterior Insula) at non-nociceptive levels of stimulus intensity. Significance IES can minimize aversive reactions of patients while ensuring spinothalamic-specific sensory assessment.
Koichi Hagiwara - One of the best experts on this subject based on the ideXlab platform.
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Insular limbic dissociation to intra epidermal electrical aδ activation a comparative study with thermo nociceptive laser stimulation
European Journal of Neuroscience, 2018Co-Authors: Maud Frot, Hélène Bastuji, Caroline Perchet, Koichi Hagiwara, Luis GarcialarreaAbstract:: Intra-epidermal electrical stimulation (IEES) has been shown to activate selectively Aδ fibers subserving spinothalamic-mediated sensations. Owing to electrically induced highly synchronous afferent volleys, IEES induces Aδ-mediated evoked potentials at nonpainful intensities, contrasting with thermo-nociceptive laser pulses which entail painful pricking sensations. Here, we recorded intracortical responses from sensory and limbic-cognitive regions of human subjects in response to IEE and laser stimuli, in order to test the hypothesis that IEES could dissociate the sensory from nonsensory networks of nociceptive processing. Intracortical evoked potentials were obtained in 11 epileptic patients with stereotactically implanted electrodes in sensory regions receiving spinothalamic afferents (Posterior Insula), limbic regions receiving spino-parabrachial input (amygdalar nucleus), and high-order affective-cognitive regions (anteromedial frontal cortex, including perigenual anterior cingulate and rostromedial prefrontal areas). Responses in the sensory Posterior Insula were of similar amplitude and latency to IEE and laser stimuli (after accounting for heat-transduction time of laser), and consistent in both cases with spinothalamic activation. However, responses to IEES in the amygdala and the anteromedial frontal regions were inconsistent and significantly smaller compared to those evoked to the laser stimulation. Thus, IEES can effectively activate the spinothalamic-sensory system with little recruitment of affective-motivational networks, including those triggered by spino-parabrachio-amygdalar projections. The fact that identical sensory responses were associated to either painful or nonpainful percepts underscores that subjective pain perception is not solely dependent on the sensory recruitment, but rather on the combined activation of sensory, limbic and cognitive areas with precise spatiotemporal relations.
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Convergence of sensory and limbic noxious input into the anterior Insula and the emergence of pain from nociception
Nature Publishing Group, 2018Co-Authors: Hélène Bastuji, Maud Frot, Caroline Perchet, Koichi Hagiwara, Luis Garcia-larreaAbstract: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’
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o1 comparison between intra epidermal electrical and laser stimulations an intracranial evoked potential study
Clinical Neurophysiology, 2017Co-Authors: Koichi Hagiwara, Maud Frot, Hélène Bastuji, Caroline Perchet, Luis GarcialarreaAbstract:Objectives Intra-epidermal electrical stimulation (IES) is considered to stimulate selectively and directly A δ fibres, by-passing the heat-mediated receptor process of laser stimulation. However, there has been only extra-cranial data to argue such fiber selectivity. Here, we recorded intracranial responses to IE and laser stimulations, to assess whether the two types of stimulation can demonstrate identical responses in precisely-localized brain regions. Methods We analysed intracranial evoked potentials to IE and laser (Nd:YAP) stimulations in 11 epileptic patients with stereotactically-implanted electrodes in the spinothalamic-receiving Posterior Insula (12 contacts) and affective-cognitive regions (amygdala, 8 contacts; anteromedial frontal region, 13 contacts). Results While both IE and laser stimuli were perceived as ‘pricking’ sensations, those elicited by IES were of lesser intensity and intrusiveness. In the Posterior Insula, IES-evoked and laser-evoked potentials were similar in waveform and amplitude. Peak-latencies were significantly shorter for IES than for laser, the mean latency difference being of 15.8 ms. In both the amygdala and anteromedial frontal regions, amplitudes were significantly attenuated for IES, as compared to laser. Discussion The latency difference in the Posterior Insula was concordant with the heat-transduction time of laser, suggesting the ability of IES to activate selectively the spinothalamic system. The depressed activations in the amygdala and anteromedial frontal regions, while preserved in the Posterior sensory Insula, were compatible with modest attentional-affective drive for IES. Conclusions IES can effectively activate the A δ -mediated sensory-encoding system (Posterior Insula) at non-nociceptive levels of stimulus intensity. Significance IES can minimize aversive reactions of patients while ensuring spinothalamic-specific sensory assessment.
Irene Tracey - One of the best experts on this subject based on the ideXlab platform.
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neural basis of induced phantom limb pain relief
Annals of Neurology, 2019Co-Authors: Irene Tracey, Melvin Mezue, Sanne Kikkert, Jacinta Oshea, David Henderson Slater, Heidi Johansenberg, Tamar R MakinAbstract:Objective Phantom limb pain (PLP) is notoriously difficult to treat, partly due to an incomplete understanding of PLP-related disease mechanisms. Noninvasive brain stimulation (NIBS) is used to modulate plasticity in various neuropathological diseases, including chronic pain. Although NIBS can alleviate neuropathic pain (including PLP), both disease and treatment mechanisms remain tenuous. Insight into the mechanisms underlying both PLP and NIBS-induced PLP relief is needed for future implementation of such treatment and generalization to related conditions. Methods We used a within-participants, double-blind, and sham-controlled design to alleviate PLP via task-concurrent NIBS over the primary sensorimotor missing hand cortex (S1/M1). To specifically influence missing hand signal processing, amputees performed phantom hand movements during anodal transcranial direct current stimulation. Brain activity was monitored using neuroimaging during and after NIBS. PLP ratings were obtained throughout the week after stimulation. Results A single session of intervention NIBS significantly relieved PLP, with effects lasting at least 1 week. PLP relief associated with reduced activity in the S1/M1 missing hand cortex after stimulation. Critically, PLP relief and reduced S1/M1 activity correlated with preceding activity changes during stimulation in the mid- and Posterior Insula and secondary somatosensory cortex (S2). Interpretation The observed correlation between PLP relief and decreased S1/M1 activity confirms our previous findings linking PLP with increased S1/M1 activity. Our results further highlight the driving role of the mid- and Posterior Insula, as well as S2, in modulating PLP. Lastly, our novel PLP intervention using task-concurrent NIBS opens new avenues for developing treatment for PLP and related pain conditions. ANN NEUROL 2019;85:59-73.
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corrigendum the dorsal Posterior Insula subserves a fundamental role in human pain
Nature Neuroscience, 2015Co-Authors: Andrew R Segerdahl, Melvin Mezue, Thomas W Okell, John T Farrar, Irene TraceyAbstract:Nat. Neurosci. 18, 499–500 (2015); published online 9 March 2015; corrected after print 26 March 2015 In the version of this article initially published, the labels were reversed for the solid and dotted lines in Figure 2c. The error has been corrected in the HTML and PDF versions of the article.
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the dorsal Posterior Insula is not an island in pain but subserves a fundamental role response to evidence against pain specificity in the dorsal Posterior Insula by davis et al
F1000Research, 2015Co-Authors: Andrew R Segerdahl, Melvin Mezue, Thomas W Okell, John T Farrar, Irene TraceyAbstract:An interesting and valuable discussion has arisen from our recent article (Segerdahl, Mezue et al., 2015) and we are pleased here to have the opportunity to expand on the various points we made. Equally important, we wish to correct several important misunderstandings that were made by Davis and colleagues that possibly contributed to their concerns about power when assessing our paper (e.g. actual subject numbers used in control experiment and the reality of the signal-to-noise and sampling of the multi-TI technique we employed). Here, we clarify the methods and analysis plus discuss how we interpret the data in the Brief Communication noting that the extrapolation and inferences made by Davis and colleagues are not consistent with our report or necessarily, in our opinion, what the data supports. We trust this reassures the F1000Research readership regarding the robustness of our results and what we actually concluded in the paper regarding their possible meaning. We are pleased, though, that Davis and colleagues have used our article to raise an important discussion around pain perception, and here offer some further insights towards that broader discussion.
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the dorsal Posterior Insula subserves a fundamental role in human pain
Nature Neuroscience, 2015Co-Authors: Andrew R Segerdahl, Melvin Mezue, Thomas W Okell, John T Farrar, Irene TraceyAbstract:Using a quantitative perfusion imaging technique, the authors investigated in healthy humans what brain regions encode a slowly varying tonic pain state. Only a small region in the contralateral dorsal Posterior Insula tracked the full pain experience, suggesting it is the homolog of a nociception-specific region found in animals.
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multiple somatotopic representations of heat and mechanical pain in the operculo Insular cortex a high resolution fmri study
Journal of Neurophysiology, 2010Co-Authors: Ulf Baumgartner, Rolfdetlef Treede, Gian Domenico Iannetti, L Zambreanu, Peter Stoeter, Irene TraceyAbstract:Whereas studies of somatotopic representation of touch have been useful to distinguish multiple somatosensory areas within primary (SI) and secondary (SII) somatosensory cortex regions, no such analysis exists for the representation of pain across nociceptive modalities. Here we investigated somatotopy in the operculo-Insular cortex with noxious heat and pinprick stimuli in 11 healthy subjects using high-resolution (2 × 2 × 4 mm) 3T functional magnetic resonance imaging (fMRI). Heat stimuli (delivered using a laser) and pinprick stimuli (delivered using a punctate probe) were directed to the dorsum of the right hand and foot in a balanced design. Locations of the peak fMRI responses were compared between stimulation sites (hand vs. foot) and modalities (heat vs. pinprick) within four bilateral regions of interest: anterior and Posterior Insula and frontal and parietal operculum. Importantly, all analyses were performed on individual, non-normalized fMRI images. For heat stimuli, we found hand-foot somatotopy in the contralateral anterior and Posterior Insula [hand, 9 ± 10 (SD) mm anterior to foot, P < 0.05] and in the contralateral parietal operculum (SII; hand, 7 ± 10 mm lateral to foot, P < 0.05). For pinprick stimuli, we also found somatotopy in the contralateral Posterior Insula (hand, 9 ± 10 mm anterior to foot, P < 0.05). Furthermore, the response to heat stimulation of the hand was 11 ± 12 mm anterior to the response to pinprick stimulation of the hand in the contralateral (left) anterior Insula (P < 0.05). These results indicate the existence of multiple somatotopic representations for pain within the operculo-Insular region in humans, possibly reflecting its importance as a sensory-integration site that directs emotional responses and behavior appropriately depending on the body site being injured.
Maud Frot - One of the best experts on this subject based on the ideXlab platform.
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Insular limbic dissociation to intra epidermal electrical aδ activation a comparative study with thermo nociceptive laser stimulation
European Journal of Neuroscience, 2018Co-Authors: Maud Frot, Hélène Bastuji, Caroline Perchet, Koichi Hagiwara, Luis GarcialarreaAbstract:: Intra-epidermal electrical stimulation (IEES) has been shown to activate selectively Aδ fibers subserving spinothalamic-mediated sensations. Owing to electrically induced highly synchronous afferent volleys, IEES induces Aδ-mediated evoked potentials at nonpainful intensities, contrasting with thermo-nociceptive laser pulses which entail painful pricking sensations. Here, we recorded intracortical responses from sensory and limbic-cognitive regions of human subjects in response to IEE and laser stimuli, in order to test the hypothesis that IEES could dissociate the sensory from nonsensory networks of nociceptive processing. Intracortical evoked potentials were obtained in 11 epileptic patients with stereotactically implanted electrodes in sensory regions receiving spinothalamic afferents (Posterior Insula), limbic regions receiving spino-parabrachial input (amygdalar nucleus), and high-order affective-cognitive regions (anteromedial frontal cortex, including perigenual anterior cingulate and rostromedial prefrontal areas). Responses in the sensory Posterior Insula were of similar amplitude and latency to IEE and laser stimuli (after accounting for heat-transduction time of laser), and consistent in both cases with spinothalamic activation. However, responses to IEES in the amygdala and the anteromedial frontal regions were inconsistent and significantly smaller compared to those evoked to the laser stimulation. Thus, IEES can effectively activate the spinothalamic-sensory system with little recruitment of affective-motivational networks, including those triggered by spino-parabrachio-amygdalar projections. The fact that identical sensory responses were associated to either painful or nonpainful percepts underscores that subjective pain perception is not solely dependent on the sensory recruitment, but rather on the combined activation of sensory, limbic and cognitive areas with precise spatiotemporal relations.
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Convergence of sensory and limbic noxious input into the anterior Insula and the emergence of pain from nociception
Nature Publishing Group, 2018Co-Authors: Hélène Bastuji, Maud Frot, Caroline Perchet, Koichi Hagiwara, Luis Garcia-larreaAbstract: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’
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o1 comparison between intra epidermal electrical and laser stimulations an intracranial evoked potential study
Clinical Neurophysiology, 2017Co-Authors: Koichi Hagiwara, Maud Frot, Hélène Bastuji, Caroline Perchet, Luis GarcialarreaAbstract:Objectives Intra-epidermal electrical stimulation (IES) is considered to stimulate selectively and directly A δ fibres, by-passing the heat-mediated receptor process of laser stimulation. However, there has been only extra-cranial data to argue such fiber selectivity. Here, we recorded intracranial responses to IE and laser stimulations, to assess whether the two types of stimulation can demonstrate identical responses in precisely-localized brain regions. Methods We analysed intracranial evoked potentials to IE and laser (Nd:YAP) stimulations in 11 epileptic patients with stereotactically-implanted electrodes in the spinothalamic-receiving Posterior Insula (12 contacts) and affective-cognitive regions (amygdala, 8 contacts; anteromedial frontal region, 13 contacts). Results While both IE and laser stimuli were perceived as ‘pricking’ sensations, those elicited by IES were of lesser intensity and intrusiveness. In the Posterior Insula, IES-evoked and laser-evoked potentials were similar in waveform and amplitude. Peak-latencies were significantly shorter for IES than for laser, the mean latency difference being of 15.8 ms. In both the amygdala and anteromedial frontal regions, amplitudes were significantly attenuated for IES, as compared to laser. Discussion The latency difference in the Posterior Insula was concordant with the heat-transduction time of laser, suggesting the ability of IES to activate selectively the spinothalamic system. The depressed activations in the amygdala and anteromedial frontal regions, while preserved in the Posterior sensory Insula, were compatible with modest attentional-affective drive for IES. Conclusions IES can effectively activate the A δ -mediated sensory-encoding system (Posterior Insula) at non-nociceptive levels of stimulus intensity. Significance IES can minimize aversive reactions of patients while ensuring spinothalamic-specific sensory assessment.
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Human SII and Posterior Insula Differently Encode Thermal Laser Stimuli
Cerebral Cortex, 2006Co-Authors: Maud Frot, François Mauguière, Luis Garcia-larrea, Michel MagninAbstract:The SII area and the Posterior Insular region are both activated by thermal stimuli in functional imaging studies. However, controversy remains as to a possible differential encoding of thermal intensity by each of these 2 contiguous areas. Using CO(2) laser stimulations, we analyzed the modifications induced by increasing thermal energy on evoked potentials recorded with electrodes implanted within SII and Posterior Insula in patients referred for presurgical evaluation of epilepsy. Although increasing stimulus intensities enhanced both SII and Insular responses, the "dynamics" of their respective amplitude changes were different. SII responses were able to encode gradually the intensity of stimuli from sensory threshold up to a level next to pain threshold but tended to show a ceiling effect for higher painful intensities. In contrast, the Posterior Insular cortex failed to detect nonnoxious laser pulses but reliably encoded stimulus intensity variations at painful levels, without showing saturation effects for intensities above pain threshold. According to these results, one can assume that Insular cortex could be more involved in the triggering of affective recognition of, and motor reaction to, noxious stimuli, whereas SII would be more dedicated to finer-grain discrimination of stimulus intensity, from nonpainful to painful levels.
François Mauguière - One of the best experts on this subject based on the ideXlab platform.
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pain syndromes and the parietal lobe
Handbook of Clinical Neurology, 2018Co-Authors: Luis Garcialarrea, François MauguièreAbstract:Pain was considered to be integrated subcortically during most of the 20th century, and it was not until 1956 that focal injury to the parietal opercular-Insular cortex was shown to produce selective loss of pain senses. The parietal operculum and adjacent Posterior Insula are the main recipients of spinothalamic afferents in primates. The innermost operculum appears functionally associated with the Posterior Insula and can be segregated histologically, somatotopically and neurochemically from the more lateral S2 areas. The Posterior Insula and Medial Operculum (PIMO) encompass functional networks essential to initiate cortical nociceptive processing. Destruction of this region selectively abates pain sensations; direct stimulation generates acute pain, and epileptic foci trigger painful seizures. Lesions of the PIMO have also high potential to develop central pain with dissociated loss of pain and temperature. The PIMO region behaves as a somatosensory area on its own, which handles phylogenetically old somesthetic capabilities based on thinly myelinated or unmyelinated inputs. It integrates spinothalamic-driven information - not only nociceptive but also innocuous heat and cold, crude touch, itch, and possibly viscero-somatic interoception. Conversely, proprioception, graphesthesia or stereognosis are not processed in this area but in S1 cortices. Given its anatomo-functional properties, thalamic connections, and tight relations with limbic and multisensory cortices, the region comprising the inner parietal operculum and Posterior Insula appears to contain a third somatosensory cortex contributing to the spinothalamic attributes of the final perceptual experience.
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Vestibular responses to direct stimulation of the human Insular cortex
Annals of neurology, 2014Co-Authors: Laure Mazzola, Isabelle Faillenot, François Mauguière, Christophe Lopez, Florian Chouchou, Jean IsnardAbstract:Objective: The present study provides a functional mapping of vestibular responses in the human Insular cortex. Methods: A total of 642 electrical stimulations of the Insula were performed in 219 patients, using stereotactically implanted depth electrodes, during the presurgical evaluation of drug-refractory partial epilepsy. We retrospectively identified 41 contacts where stimulation elicited vestibular sensations (VSs) and analyzed their location with respect to (1) their stereotactic coordinates (for all contacts), (2) the anatomy of Insula gyri (for 20 vestibular sites), and (3) the probabilistic cytoarchitectonic maps of the Insula (for 9 vestibular sites). Results: VSs occurred in 7.6% of the 541 evoked sensations after electrical stimulations of the Insula. VSs were mostly obtained after stimulation of the Posterior Insula, that is, in the granular Insular cortex and the postcentral Insular gyrus. The data also suggest a spatial segregation of the responses in the Insula, with the rotatory and translational VSs being evoked at more Posterior stimulation sites than other less definable VSs. No left-right differences were observed. Interpretation: These results demonstrate vestibular sensory processing in the Insula that is centered on its Posterior part. The present data add to the understanding of the multiple sensory functions of the Insular cortex and of the cortical processing of vestibular signals. The data also indicate that lesion or dysfunction in the Posterior Insula should be considered during the evaluation of vestibular epileptic seizures.
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Human SII and Posterior Insula Differently Encode Thermal Laser Stimuli
Cerebral Cortex, 2006Co-Authors: Maud Frot, François Mauguière, Luis Garcia-larrea, Michel MagninAbstract:The SII area and the Posterior Insular region are both activated by thermal stimuli in functional imaging studies. However, controversy remains as to a possible differential encoding of thermal intensity by each of these 2 contiguous areas. Using CO(2) laser stimulations, we analyzed the modifications induced by increasing thermal energy on evoked potentials recorded with electrodes implanted within SII and Posterior Insula in patients referred for presurgical evaluation of epilepsy. Although increasing stimulus intensities enhanced both SII and Insular responses, the "dynamics" of their respective amplitude changes were different. SII responses were able to encode gradually the intensity of stimuli from sensory threshold up to a level next to pain threshold but tended to show a ceiling effect for higher painful intensities. In contrast, the Posterior Insular cortex failed to detect nonnoxious laser pulses but reliably encoded stimulus intensity variations at painful levels, without showing saturation effects for intensities above pain threshold. According to these results, one can assume that Insular cortex could be more involved in the triggering of affective recognition of, and motor reaction to, noxious stimuli, whereas SII would be more dedicated to finer-grain discrimination of stimulus intensity, from nonpainful to painful levels.