A Distributed Neural Recorder/Stimulator for Epilepsy Monitoring

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The potential of neurostimulation to improve quality of life is now well established with examples such as Pacemakers (cardiac arrhythmia), cochlear implants (deafness), deep brain stimulators (Parkinson's treatment) and chronic pain. The global medical neuromodulation market is set to reach $10B by 2024.Epilepsy, characterized by abnormal and excessive brain activity which can lead to violent seizures, affects between 0.5-1% of the population (2.5 M people in United States, ~225k in Canada). As much as 30% of epilepsy patients suffer from intractable drug-resistant epilepsy and can benefit from neurostimulation. Recent research demonstrated seizure forecasting within 24 hours of occurrence, giving the opportunity for seizure mitigative measures and adjustment of activities. However, long-term neural recording/stimulation at multiple cortical targets is still challenging. Among the most challenging aspects of such an implantable device is the acquisition and transmission of data simultaneously from thousands of electrodes distributed at different cortical sites within a practical and clinically safe power budget. This project seeks to develop an application specific integrated circuit (ASIC) targeting epilepsy that will enable neurorecording/stimulation devices with single-neuron resolution, on-chip spike characterization (amplitude and shape) and stimulus pulse shaping, while wirelessly transmitting the compressed data using an algebraic coding scheme. The target implant for this device comprises four ASICS, implanted in the brain at cortical sites suitable for seizure prediction. These ASICs are wired to a central wireless communication hub that transmits the compressed information to an external computer worn by the patient. Unlike other epilepsy recorders limited to few tens of electrodes distributed on an area of few mm2, each integrated circuit is <1 mm2, and will simultaneously records spikes from 1600 channels at a 20 µm pitch. In collaboration with our commercial partners we are creating the first synchronized and distributed 6400-electrode neurorecorder/stimulator system suitable for safe, life-long implantation.This project is conducted in collaboration with Gezell (Gatineau, Canada), the University of Melbourne (Australia) and their industrial partner Carbon Cybernetics Inc. (Melbourne, Australia), who are pioneering very high resolution, 100% biocompatible electrode technology, ultrananocrystalline diamond enclosures and epilepsy prediction algorithms. This partnership perfectly complements our teams composed of the Université de Sherbrooke (Sherbrooke, Canada) and Gezell inc. (Gatineau, Canada) with expertise in microelectronics and product development.