- Institute of Neuroscience (IONS)
Université catholique de Louvain
53, Avenue Mounier (UCL53.75)
B1200, Brussels, Belgium - +32 2 764 9349
- Gamma Band Oscillations, Somatosensory Neuroscience, Event-Related Potentials, Pain, Neuroscience, Thermal Nociception, and 6 moreIndependent Component Analysis, Chronic Pain, Steady State Visual Evoked Potentials, Functional Magnetic Resonance Imaging, Electroencephalography, and Dynamic Causal Modellingedit
- My main research interest is to understand how the human brain processes nociceptive sensory input, and how this lead... moreMy main research interest is to understand how the human brain processes nociceptive sensory input, and how this leads to the perception of pain.
See also : Letswave, a free, open-source EEG signal-processing toolbox, developed to perform fast multi-subject analysis of event-related potentials and steady-state evoked potentials with specific focus on time-frequency and single-trial analysis methods. http://nocions.webnode.com/letswaveedit
Background IMI2-PainCare-BioPain-RCT3 is one of four similarly designed clinical studies aiming at profiling a set of functional biomarkers of drug effects on the nociceptive system that could serve to accelerate the future development of... more
Background IMI2-PainCare-BioPain-RCT3 is one of four similarly designed clinical studies aiming at profiling a set of functional biomarkers of drug effects on the nociceptive system that could serve to accelerate the future development of analgesics, by providing a quantitative understanding between drug exposure and effects of the drug on nociceptive signal processing in human volunteers. IMI2-PainCare-BioPain-RCT3 will focus on biomarkers derived from non-invasive electroencephalographic (EEG) measures of brain activity. Methods This is a multisite single-dose, double-blind, randomized, placebo-controlled, 4-period, 4-way crossover, pharmacodynamic (PD) and pharmacokinetic (PK) study in healthy subjects. Biomarkers derived from scalp EEG measurements (laser-evoked brain potentials [LEPs], pinprick-evoked brain potentials [PEPs], resting EEG) will be obtained before and three times after administration of three medications known to act on the nociceptive system (lacosamide, pregaba...
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Anesthesie-Reanimation - Epreuve corrigee par l'auteur. Disponible en ligne depuis le 06/03/2018
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g. hand movements to feel a texture or identify an object). These exploratory movements are often rhythmic, and it has been suggested... more
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g. hand movements to feel a texture or identify an object). These exploratory movements are often rhythmic, and it has been suggested that movement-perception shaping could be supported by movement-induced neural entrainment. In auditory perception, the shaping of perception by movement has been reported in humans using behavioral methods, but neurophysiological evidence is lacking. To fill this gap, we took advantage of a specific context, music. Participants listened to a cyclical rhythm before and after moving the body on this rhythm according to a specific meter. We found that the brain responses to the rhythm as recorded with EEG after body movement was significantly enhanced at meter frequencies to which participants had moved. These results provide evidence that body movement can shape selectively the subsequent perception and neural representation of auditory rhythms.
Whether the cortical processing of nociceptive input relies on the activity of nociceptive-specific neurons or whether it relies on the activity of non-specific neuronal populations remains a matter of intense debate. Here, we address... more
Whether the cortical processing of nociceptive input relies on the activity of nociceptive-specific neurons or whether it relies on the activity of non-specific neuronal populations remains a matter of intense debate. Here, we address this question using EEG “frequency-tagging” of steady-state evoked potentials (SS-EPs) combined with an intermodal selective attention paradigm to test whether the cortical processing of nociceptive input relies on nociceptive-specific neuronal populations which can be selectively modulated by top-down attention. Specifically, we hypothesized that if the cortical processing of nociceptive and non-nociceptive sensory inputs involves distinct neuronal populations, selective attention would selectively enhance the SS-EPs elicited by the attended stream of sensory input. Conversely, if the cortical processing of the two sensory inputs involves the same neuronal populations, selective attention would indistinctly enhance the responses elicited by the attend...
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A recent animal study showed that high frequency electrical stimulation (HFS) of C-fibres induces a gliogenic heterosynaptic long-term potentiation at the spinal cord that is hypothesized to mediate secondary hyperalgesia in humans. Here... more
A recent animal study showed that high frequency electrical stimulation (HFS) of C-fibres induces a gliogenic heterosynaptic long-term potentiation at the spinal cord that is hypothesized to mediate secondary hyperalgesia in humans. Here this hypothesis was tested by predominantly activating C-fibre nociceptors in the area of secondary mechanical hyperalgesia induced by HFS in humans. It is shown that heat perception elicited by stimuli predominantly activating C-fibre nociceptors is greater, as compared to the control site, after HFS in the area of secondary mechanical hyperalgesia. This is the first study that confirms in humans the involvement of C-fibre nociceptors in the changes in heat sensitivity in the area of secondary mechanical hyperalgesia induced by HFS. It has recently been shown that high frequency electrical stimulation (HFS) of C-fibres induces a gliogenic heterosynaptic long-term potentiation (LTP) at the spinal cord in animals, which has been hypothesized to be th...
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Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we examined whether dexterous manipulation, a highly habitual and seemingly automatic behavior, involves high order cognitive functions.... more
Simultaneous execution of cognitive and sensorimotor tasks is critical in daily life. Here, we examined whether dexterous manipulation, a highly habitual and seemingly automatic behavior, involves high order cognitive functions. Specifically, we explored the impact of reducing available cognitive resources on the performance of a precision grip-lift task in healthy participants of three age groups (18-30, 30-60 and 60-75 years). Participants performed a motor task in isolation (M), in combination with a low-load cognitive task (M + L), and in combination with a high-load cognitive task (M + H). The motor task consisted in grasping, lifting and holding an apparatus instrumented with force sensors to monitor motor task performance. In the cognitive task, a list of letters was shown briefly before the motor task. After completing the motor task, one letter of the list was shown, and participants reported the following letter of the list. In M + L, letters in the list followed the alpha...
When we touch an object or explore a texture, frictional strains are induced by the tactile interactions with the surface of the object. Little is known about how these interactions are perceived, although it becomes crucial for the... more
When we touch an object or explore a texture, frictional strains are induced by the tactile interactions with the surface of the object. Little is known about how these interactions are perceived, although it becomes crucial for the nascent industry of interactive displays with haptic feedback (e.g. smartphones and tablets) where tactile feedback based on friction modulation is particularly relevant. To investigate the human perception of frictional strains, we mounted a high-fidelity friction modulating ultrasonic device on a robotic platform performing controlled rubbing of the fingertip and asked participants to detect induced decreases of friction during a forced-choice task. The ability to perceive the changes in friction was found to follow Weber's Law of just noticeable differences, as it consistently depended on the ratio between the reduction in tangential force and the pre-stimulation tangential force. The Weber fraction was 0.11 in all conditions demonstrating a very ...
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To investigate whether cool-evoked potentials (CEP) elicited by brisk innocuous cooling of the skin could serve as an alternative to laser-evoked potentials (LEP), currently considered as the best available neurophysiological tool to... more
To investigate whether cool-evoked potentials (CEP) elicited by brisk innocuous cooling of the skin could serve as an alternative to laser-evoked potentials (LEP), currently considered as the best available neurophysiological tool to assess the spinothalamic tract and diagnose neuropathic pain. A novel device made of micro-Peltier elements and able to cool the skin at -300 °C/s was used to record CEPs elicited by stimulation of the hand dorsum in 40 healthy individuals, characterize the elicited responses, and assess their signal-to-noise ratio. Various stimulation surfaces (40 mm and 120 mm), cooling ramps (-200 °C/s and -133 °C/s) and temperature steps (20 °C, 15 °C, 10 °C, 5 °C) were tested to identify optimal stimulation conditions. CEPs were observed in all conditions and subjects, characterized by a biphasic negative-positive complex maximal at the vertex (Cz), peaking 190-400 ms after stimulus onset, preceded by a negative wave over central-parietal areas contralateral to the...
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Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs), which reflect the activity of both modality-specific and supramodal cortical generators overlapping in time and space. When stimuli... more
Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs), which reflect the activity of both modality-specific and supramodal cortical generators overlapping in time and space. When stimuli are delivered at long and variable intervals (10-15 seconds), supramodal components appear as a large negative-positive biphasic deflection maximal at the scalp vertex (vertex wave) and dominate over modality-specific components. Stimulus repetition at 1 Hz induces a strong habituation of these supramodal components, which largely reflect stimulus saliency and behavioural relevance. However, the effect of stimulus repetition on lateralized modality-specific components is less clear. To comprehensively characterize how the different ERP waves habituate over time, we recorded the ERPs elicited by 60 identical somatosensory stimuli (either non-nociceptive Aβ or nociceptive Aδ), delivered at 1 Hz to healthy human participants. We show that the well-descr...
The human auditory system presents a remarkable ability to detect rapid changes in fast, continuous acoustic sequences, as best illustrated in speech and music. However, the neural processing of rapid auditory contrast remains largely... more
The human auditory system presents a remarkable ability to detect rapid changes in fast, continuous acoustic sequences, as best illustrated in speech and music. However, the neural processing of rapid auditory contrast remains largely unclear, probably due to the lack of methods to objectively dissociate the response components specifically related to the contrast from the other components in response to the sequence of fast continuous sounds. To overcome this issue, we tested a novel use of the frequency-tagging approach allowing contrast-specific neural responses to be tracked based on their expected frequencies. The EEG was recorded while participants listened to 40-s sequences of sounds presented at 8Hz. A tone or interaural time contrast was embedded every fifth sound (AAAAB), such that a response observed in the EEG at exactly 8 Hz/5 (1.6 Hz) or harmonics should be the signature of contrast processing by neural populations. Contrast-related responses were successfully identifi...
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Sensitization is a form of implicit learning produced by the exposure to a harmful stimulus. In humans and other mammals, sensitization after skin injury increases the responsiveness of peripheral nociceptors and enhances the synaptic... more
Sensitization is a form of implicit learning produced by the exposure to a harmful stimulus. In humans and other mammals, sensitization after skin injury increases the responsiveness of peripheral nociceptors and enhances the synaptic transmission of nociceptive input in the central nervous system. Here, we show that sensitization-related changes in the central nervous system are not restricted to nociceptive pathways and, instead, also affect other sensory modalities, especially if that modality conveys information relevant for the sensitized body part. Specifically, we show that after sensitizing the forearm using high-frequency electrical stimulation (HFS) of the skin, visual stimuli projected onto the sensitized forearm elicit significantly enhanced brain responses. Whereas mechanical hyperalgesia was present both 20 and 45 minutes after HFS, the enhanced responsiveness to visual stimuli was present only 20 minutes after HFS. Taken together, our results indicate that sensitizati...
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The role of the primary somatosensory cortex (S1) in vibrotaction is well established. In contrast, its involvement in nociception remains debated. Here, we test whether S1 is similarly involved in the processing of non-nociceptive and... more
The role of the primary somatosensory cortex (S1) in vibrotaction is well established. In contrast, its involvement in nociception remains debated. Here, we test whether S1 is similarly involved in the processing of non-nociceptive and nociceptive somatosensory input in humans by comparing the after-effects of high-definition transcranial direct current stimulation (HD-tDCS) of the primary sensorimotor cortex on the event-related potentials (ERPs) elicited by non-nociceptive and nociceptive somatosensory stimuli delivered to the ipsilateral and contralateral hand. Cathodal HD-tDCS significantly affected the responses to non-nociceptive somatosensory stimuli delivered to the contralateral hand: both early-latency ERPs from within S1 (N20 wave elicited by transcutaneous electrical stimulation of the median nerve) and late-latency ERPs elicited outside S1 (N120 wave elicited by short-lasting mechanical vibrations delivered to the index fingertip, thought to originate from bilateral ope...
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The recording of event-related brain potentials triggered by a transient heat stimulus is used extensively to study nociception and diagnose lesions or dysfunctions of the nociceptive system in humans. However, these responses are related... more
The recording of event-related brain potentials triggered by a transient heat stimulus is used extensively to study nociception and diagnose lesions or dysfunctions of the nociceptive system in humans. However, these responses are related exclusively to the activation of a specific subclass of nociceptive afferents: quickly-adapting thermonociceptors. In fact, except if the activation of Aδ fibers is avoided or if A fibers are blocked, these responses specifically reflect activity triggered by the activation of Type 2 quickly-adapting A fiber mechano-heat nociceptors (AMH-2). Here, we propose a novel method to isolate, in the human electroencephalogram (EEG), cortical activity related to the sustained periodic activation of heat-sensitive thermonociceptors, using very slow (0.2Hz) and long-lasting (75s) sinusoidal heat stimulation of the skin between baseline and 50°C. In a first experiment, we show that when such long-lasting thermal stimuli are applied to the hand dorsum of healthy volunteers, the slow rises and decreases of skin temperature elicit a consistent periodic EEG response at 0.2Hz and its harmonics, as well as a periodic modulation of the magnitude of theta, alpha and beta band EEG oscillations. In a second experiment, we demonstrate using an A fiber block that these EEG responses are predominantly conveyed by unmyelinated C fiber nociceptors. The proposed approach constitutes a novel mean to study C fiber function in humans, and to explore the cortical processing of tonic heat pain in physiological and pathological conditions.
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Transient nociceptive stimuli elicit consistent brain responses in the primary and secondary somatosensory cortices (S1, S2), the insula and the anterior and mid-cingulate cortex (ACC/MCC). However, the functional significance of these... more
Transient nociceptive stimuli elicit consistent brain responses in the primary and secondary somatosensory cortices (S1, S2), the insula and the anterior and mid-cingulate cortex (ACC/MCC). However, the functional significance of these responses, especially their relationship with sustained pain perception, remains largely unknown. Here, using functional magnetic resonance imaging, we characterize the differential involvement of these brain regions in the processing of sustained nociceptive and non-nociceptive somatosensory input. By comparing the spatial patterns of activity elicited by transient (0.5 ms) and long-lasting (15 and 30 s) stimuli selectively activating nociceptive or non-nociceptive afferents, we found that the contralateral S1 responded more strongly to the onset of non-nociceptive stimulation as compared to the onset of nociceptive stimulation and the sustained phases of nociceptive and non-nociceptive stimulation. Similarly, the anterior insula responded more stron...
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Transient nociceptive stimuli elicit consistent brain responses in the primary and secondary somatosensory cortices (S1, S2), the insula and the anterior and mid-cingulate cortex (ACC/MCC). However, the functional significance of these... more
Transient nociceptive stimuli elicit consistent brain responses in the primary and secondary somatosensory cortices (S1, S2), the insula and the anterior and mid-cingulate cortex (ACC/MCC). However, the functional significance of these responses, specially their relationship with sustained pain perception, remains largely unknown. Here, using functional magnetic resonance imaging, we characterize the differential involvement of these brain regions in the processing of sustained nociceptive and non-nociceptive somatosensory input. By comparing the spatial patterns of activity elicited by transient (0.5 ms) and long-lasting (15 and 30 s) stimuli selectively activating nociceptive or non-nociceptive afferents, we found that the contralateral S1 responded more strongly to the onset of non-nociceptive stimulation as compared to the onset of nociceptive stimulation and the sustained phases of nociceptive and non-nociceptive stimulation. Similarly, the anterior insula responded more strongl...
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It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of... more
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of auditory perception by movement in humans by taking advantage of a specific context: music. Participants listened to a repeated rhythmical sequence before and after moving their bodies to this rhythm in a specific meter. We found that the brain responses to the rhythm (as recorded with electroencephalography) after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. These results provide evidence that body movement can selectively shape the subsequent internal representation of auditory rhythms.
Research Interests:
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of... more
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of auditory perception by movement in humans by taking advantage of a specific context: music. Participants listened to a repeated rhythmical sequence before and after moving their bodies to this rhythm in a specific meter. We found that the brain responses to the rhythm (as recorded with electroencephalography) after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. These results provide evidence that body movement can selectively shape the subsequent internal representation of auditory rhythms.
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Using high-density EEG recording, sixteen observers were asked to detect a face while stimulated with only white noise (400 different templates of 32× 43 pixels, to mirror the aspect ratio of a face). Superstitious perceptions occur... more
Using high-density EEG recording, sixteen observers were asked to detect a face while stimulated with only white noise (400 different templates of 32× 43 pixels, to mirror the aspect ratio of a face). Superstitious perceptions occur whenever the observer believes that a face is ...
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F114 PARALLEL PROCESSING OF NOCICEPTIVE AND NON-NOCICEPTIVE SOMATOSENSORY INFORMATION IN S1 AND S2: EVIDENCE FROM DYNAMIC CAUSAL MODELLING OF fMRI DATA-Liang-2012-European Journal of Pain Supplements-Wiley Online Library
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S165 PHASE-LOCKED AND NON PHASE-LOCKED EEG RESPONSES ELICITED BY INTRANASAL NOCICEPTIVE CHEMOSENSORY STIMULATION TO EXPLORE TRIGEMINAL FUNCTION IN HUMANS-Huart-2012-European Journal of Pain Supplements-Wiley Online Library
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7 Abstract 8 The necessary and sufficient condition to record brain responses to signals ascending through C-9 fibers seems to be avoidance of concomitant activation of Adelta-fibers. Several explanations are 10 offered in the literature.... more
7 Abstract 8 The necessary and sufficient condition to record brain responses to signals ascending through C-9 fibers seems to be avoidance of concomitant activation of Adelta-fibers. Several explanations are 10 offered in the literature. One more is added, based on the phenomenon of post-event desynchro-11 nisation. Four methods, having in common the ability to selectively activate C-fiber afferents, are 12 currently used to obtain ultralate-laser evoked potentials (LEPs) in a reliable way and with the 13 appropriate latency. Exception ...
S165 PHASE-LOCKED AND NON PHASE-LOCKED EEG RESPONSES ELICITED BY INTRANASAL NOCICEPTIVE CHEMOSENSORY STIMULATION TO EXPLORE TRIGEMINAL FUNCTION IN HUMANS-Huart-2012-European Journal of Pain Supplements-Wiley Online Library
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F114 PARALLEL PROCESSING OF NOCICEPTIVE AND NON-NOCICEPTIVE SOMATOSENSORY INFORMATION IN S1 AND S2: EVIDENCE FROM DYNAMIC CAUSAL MODELLING OF fMRI DATA-Liang-2012-European Journal of Pain Supplements-Wiley Online Library
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Methods: Non-nociceptive (transcutaneous median nerve stimulation) and nociceptive (CO2 laser stimulation of the hand dorsum) somatosensory evoked potentials (SEPs) were recorded following stimulation of the left and right hand, before... more
Methods: Non-nociceptive (transcutaneous median nerve stimulation) and nociceptive (CO2 laser stimulation of the hand dorsum) somatosensory evoked potentials (SEPs) were recorded following stimulation of the left and right hand, before and after applying cTBS over the left or right S1 (localized using coregistration of individual MRI data) or M1 (localized based on the motor response elicited by single pulses). For each of the different peaks characterizing non-nociceptive and nociceptive SEPs, the finding of an interaction ...
Using high-density EEG recording, sixteen observers were asked to detect a face while stimulated with only white noise (400 different templates of 32× 43 pixels, to mirror the aspect ratio of a face). Superstitious perceptions occur... more
Using high-density EEG recording, sixteen observers were asked to detect a face while stimulated with only white noise (400 different templates of 32× 43 pixels, to mirror the aspect ratio of a face). Superstitious perceptions occur whenever the observer believes that a face is ...
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Thermal laser stimulation of the skin is an efficient exploratory tool to characterize the nociceptive system. In the present study, finite element simulations are done to calculate the intra-cutaneous spatio-temporal temperature profiles... more
Thermal laser stimulation of the skin is an efficient exploratory tool to characterize the nociceptive system. In the present study, finite element simulations are done to calculate the intra-cutaneous spatio-temporal temperature profiles following the delivery of such laser stimuli. The proposed computer-aided modeling considers a number of important parameters that have been disregarded in previous approaches: (i) variability of water content across the skin in both hairy and glabrous skin, (ii) temperature dependency of optical and thermal skin parameters, (iii) laser wavelength and corresponding absorption coefficient, (iv) beam shape (Gaussian vs. flat top) and (v) power emission (closed vs. open loop). Numerical simulations allow determining at each instant of time the volume and area of skin tissue whose temperature exceeds a given nociceptor activation threshold. This knowledge allows a finer characterization of the subpopulations of primary afferents that encode and convey nociceptive signals to the central nervous system. As an example, the approach is used to obtain an estimate of intraepidermal nerve fiber density in both physiological and pathological conditions. Moreover, a better knowledge of the heat distribution also reduces the risk of injury to the skin. Finally, in order to make the finite element simulations accessible to investigators with no prior background in numerical analysis, a specific open-source user-interface has been developed with the ONELAB software.
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Human studies have shown that heterotopic nociceptive conditioning stimulation (HNCS) applied to a given body location reduce the percept and brain responses elicited by noxious test stimuli delivered at a remote body location. It remains... more
Human studies have shown that heterotopic nociceptive conditioning stimulation (HNCS) applied to a given body location reduce the percept and brain responses elicited by noxious test stimuli delivered at a remote body location. It remains unclear to what extent this effect of HNCS relies on the spinal-bulbar-spinal loop mediating the effect of diffuse noxious inhibitory controls (DNIC) described in animals, and/or on top-down cortical mechanisms modulating nociception. Importantly, some studies have examined the effects of HNCS on the brain responses to nociceptive input conveyed by Aδ-fibers. In contrast, no studies have explored the effects of HNCS on the responses to selective nociceptive C-fiber input and non-nociceptive Aβ fiber input. In this study, we measured the intensity of perception and event related potentials (ERPs) to stimuli activating Aδ-, C- and Aβ-fibers, before, during and after HNCS, obtained by immersing one foot in painful cold water. We observed that (i) the perceived intensity of nociceptive Aδ- and C- stimuli was reduced during HNCS, (ii) the ERPs elicited by Aδ- and Aβ-, and C- stimuli were also reduced during HNCS. Importantly, because Aβ-ERPs are related to primary afferents that ascend directly through the dorsal columns without being relayed at spinal level, the modulation of these responses may not be explained by an influence of descending projections modulating the transmission of nociceptive input at spinal level. Therefore, our results indicate that, in humans, HNCS should be used with caution as a direct measure of DNIC-related mechanisms. This article is protected by copyright. All rights reserved.