Flexible graphene-based neurotechnology for high-precision deep brain mapping and neuromodulation in Parkinsonian rats

Deep brain stimulation (DBS) is a neuroelectronic therapy for the treatment of a broad range of neurological disorders, including Parkinson’s disease. Current DBS technologies face important limitations that impact their efficacy, such as large electrode size, invasiveness, and lack of adaptive therapy based on biomarker monitoring. The use of novel electrode materials is expected to contribute to overcome these limitations. In a previous study, we reported that nanoporous reduced graphene oxide (rGO) is a promising electrode material due to its high charge injection capacity and low impedance. Here, we investigate the potential benefits of using the rGO technology in DBS. To this end, we implant a flexible high-density array of rGO microelectrodes in the subthalamic nucleus (STN) of healthy and hemi-parkinsonian rats to investigate specific electrophysiological Parkinsonian biomarkers and to assess the effect of microscale stimulation. We demonstrate that these microelectrodes record action potentials with high signal-to-noise ratios (SNR > 6), allowing the precise localization of deep brain structures like the STN, and the tracking of multiunit-based biomarkers such as STN bursts. The bidirectional capability to deliver high-density focal stimulation and to record high-fidelity signals unlocks the visualization of the local neuromodulation of the multiunit biomarker. These findings demonstrate the potential of bidirectional high-resolution neural interfaces to investigate the mechanisms around DBS in preclinical models and suggest new avenues for the use of adaptive closed-loop operation based on electrophysiological biomarkers monitoring.