Modèle biophysique de microélectrodes pour l’enregistrement d’oscillations haute fréquence de nature épileptique

High Frequency Oscillations (HFO: 80-600 Hz) and particularly Fast-Ripples (FRs: 200-600 Hz) have gained increasing interest during the last decades as a biomarker of epileptogenic networks in patients with Drug-Resistant Epilepsy, candidate to surgery. Studies have revealed that FRs originate from small clusters of hyperexcitable neurons, requiring the use of intracerebral microelectrodes for their recording. Nonetheless, the recording of FRs using conventional metal microelectrodes remains challenging due to their small size, which increases the impedance resulting in poor signal-to-noise ratio and distortion of the signal. This thesis presents a model-guided approach for the conception of microelectrodes optimized for the recording of FRs. In particular, the coating of metal microelectrodes with a conducting polymer, namely Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is studied. A neurophysiologically-plausible computational model was used to develop a biophysical model of cerebral Electrode-Tissue Interface, which was confronted to experimental recordings in epileptic mice. Novel organic electrodes in carbon and silk that incorporate PEDOT:PSS proved their ability to record FRs in epileptic mice. Moreover, in-vivo impedance spectroscopy measures were used to investigate the electrical properties of the scar tissue that forms around the electrodes after implantation. It was determined that the scar tissue did not affect the recording of FRs. Lastly, a flexible parylene-C microelectrode array with PEDOT:PSS showed promising preliminary results. Perspectives of this work include the design of neural implants for other applications in which chronic recording over long-duration periods of time is required.