Caractérisation des réponses EEG à un stimulus douloureux avant et après induction d'une hyperalgésie secondaire

Details

Supervisors

Mouraux, André ; Standaert, François-Xavier

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical

Abstract

enAbstract Objective: Through this thesis, we want to characterize more precisely the response to a painful stimulus in case of secondary hyperalgesia. To that end, we build on an earlier study and consider two new approaches. On the one hand, the habituation rhythms and on the other hand the cortical microstates. Experiment and Data: Secondary hyperalgesia is induced by high frequency electrical stimulation (HFS) on one arm of each of the 16 healthy volunteers. EEG responses following a mechanical pinprick stimulus are recorded for both arms, before and after HFS. These measurements are repeated 30 times. Habituation: No phenomenon of habituation during the repetitions could be highlighted. Nevertheless, it is plausible that habituation appears early, and therefore cannot detected. Regarding habituation to sensitization, a phenomenon of interaction between secondary hyperalgesia induced by HFS and other painful mechanical stimuli was highlighted. In that respect, it appears that the amplitude of the response to the pain stimulus decreases when another painful event of the same type occurs between the sensitization and stimulation of the sensitized area. Microstates: A method for the application of microstate analysis to experimental data has been formalized with several metrics. This method revealed that two microstates, a frontal and a frontal-occipital median, characterized all the signals. Statistical analyzes of the characteristics of these microstates have shown that the response to the pain stimulus is not only amplified in the presence of secondary hyperalgesia. Its physiognomy is also modified and is characterized by the increased presence of the frontal topography. In addition, the influence of secondary hyperalgesia on cerebral states of rest activity is also significant. It then results in a decrease in transitions from one state to another. Conclusion: The brain mechanisms governing secondary hyperalgesia are complex and strongly interrelated with other mechanisms. The microstate analysis has proved its interest in the analysis of ERP's signals. The information contained in the microstates is indeed different from the one used in conventional techniques such as time and frequency analysis.