Biology subjects

Mouraux, A.

Publications and source records attributed to Mouraux, A..

3 recordsLinked to original sources

bioRxiv2018

Central sensitization increases the pupil dilation elicited by mechanical pinprick stimulation

High frequency electrical stimulation (HFS) of skin nociceptors triggers central sensitization, manifested as increased pinprick sensitivity of the skin surrounding the site at which HFS was applied. The aim of the present study was to compare the effects of HFS on pupil dilation and brain responses elicited by pinprick stimulation delivered in the area of increased pinprick sensitivity. In fourteen healthy volunteers HFS was applied to one of the two forearms. Before and twenty minutes after applying HFS, mechanical pinprick stimuli (64 mN and 96 mN) were delivered to the area surrounding the site at which HFS was applied as well as the contralateral control arm. During pinprick stimulation both the pupil size and electroencephalogram were recorded. HFS induced a clear and comparable increase in pinprick sensitivity for both the 64 and 96 mN stimulation intensity. Both pinprick stimulation intensities elicited a greater pupil dilation response when delivered to the area of increased pinprick sensitivity. However, this greater pupil dilation response was larger for the 64 mN compared to the 96 mN stimulation intensity. A similar pattern was observed for the negative wave of the pinprick-evoked brain potentials (PEPs), however, the increase was not significant for the 96 mN and showed only a trend towards significance for the 64 mN. These results show that there is a correspondence between the increase in pupil dilation and the increase in PEPs, but that pupil size is a more sensitive measure for detecting the effects of central sensitization than PEPs.

neuroscience↗

bioRxiv2018

High frequency electrical stimulation induces a long-lasting enhancement of event-related potentials but does not change the perception elicited by intra-epidermal electrical stimuli delivered to the area of secondary mechanical hyperalgesia

High frequency electrical stimulation (HFS) of the skin induces increased pinprick sensitivity in the surrounding unconditioned skin (secondary hyperalgesia). Moreover, it has been shown that brief high intensity CO2 laser stimuli, activating both A{delta}- and C-fiber nociceptors, are perceived as more intense when delivered in the area of secondary hyperalgesia. To investigate the contribution of A-fiber nociceptors to secondary hyperalgesia the present study assessed if the perception and brain responses elicited by low-intensity intra-epidermal electrical stimulation (IES), a method preferentially activating A{delta}-fiber nociceptors, are increased in the area of secondary hyperalgesia. HFS was delivered to one of the two forearms of seventeen healthy volunteers. Mechanical pinprick stimulation and IES were delivered at both arms before HFS (T0), 20 minutes after HFS (T1) and 45 minutes after HFS (T2). In all participants, HFS induced an increase in pinprick perception at the HFS-treated arm, adjacent to the site of HFS. This increase was significant at both T1 and T2. HFS did not affect the percept elicited by IES, but did enhance the magnitude of the N2 wave of IES-evoked brain potentials, both at T1 and at T2. HFS induced a long-lasting enhancement of the N2 wave elicited by IES in the area of secondary hyperalgesia, indicating that HFS enhances the responsiveness of the central nervous system to nociceptive inputs conveyed by AMH-II nociceptors. However, we found no evidence that HFS affects the perception elicited by IES, which may suggest that AMH-II nociceptors do not contribute to HFS-induced secondary hyperalgesia.

neuroscience↗

bioRxiv2017

Characterising the short-term habituation of event-related evoked potentials

Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs). Stimulus repetition at 1 Hz is known to induce a strong habituation of the largest ERP responses, the vertex waves, which are elicited by stimuli regardless of their modality7, provided that they are salient and behaviourally-relevant. In contrast, the effect of stimulus repetition on the earlier sensor)7 components of ERls has been less explored, and the few existing results are inconsistent. To characterize how the different ERP waves habituate over time, we recorded the responses elicited by 60 identical somatosensory stimuli (activating either non-nociceptive A {beta} or nociceptive A5 afferents), delivered at 1 Hz to healthy human participants. We show that the well-described spatiotemporal sequence of lateralised and vertex ERP components elicited by the first stimulus of the series is largely preserved in the smaller-amplitude, habituated response elicited by the last stimuli of the series. We also found that the earlier lateralised sensory waves habituate across the 60 trials following the same decay function of the vertex waves: this decay function is characterised by a large drop at the first stimulus repetition followed by smaller decreases at subsequent repetitions. Interestingly, the same decay functions described the habituation of ERPs elicited by repeated non-nociceptive and nociceptive stimuli. This study provides a neurophysiological characterization of the effect of prolonged and repeated stimulation on the main components of somatosensory ERPs. It also demonstrates that both lateralised waves and vertex waves are obligator}7 components of ERPs elicited by non-nociceptive and nociceptive stimuli.\n\nSignificance statementOur results provide a functional characterization of the decay of the different ERP components when identical somatosensory (nociceptive and non-nociceptive) stimuli are repeated at 1Hz. East-rising stimuli elicit ERPs obligator)7 contributed by both early lateralised components and late vertex components, even when stimulus repetition minimizes stimulus relevance. This challenges the view that lateralised waves are not obligatorily elicited by nociceptive stimuli. Furthermore, the lateralised and vertex waves habituate to stimulus repetition following similar decay functions, which are unlikely explained in terms of fatigue or adaptation of skin receptors.

neuroscience↗