2097 NeuroFlex: A Modular System of Wireless, Fully Implanted, Mechanically Flexible, High-density Subdural and Depth Electrode Arrays

INTRODUCTION: Current neural interface technologies suffer from tradeoffs between the density of electrodes, ability to sample from broad networks, and limitations on data transmission and power. Higher channel counts require percutaneous connection to external equipment or are limited by battery-powered, implanted electronics. METHODS: In the Bioelectronic Interface System to the Cortex (BISC), a fully implanted custom integrated circuit thinned to less than 20 µm supports dense recording and stimulation with wireless powering and high-throughput telemetry through an outside-the-body wearable relay station. Flexible, customizable polyimide extender depth or surface arrays are bonded to each implanted circuit with support for up to 1,024 channels. We performed initial feasibility and safety testing in a porcine model. RESULTS: Thin-film subdural arrays were implanted over the sensorimotor cortex and depth electrodes from sensory cortex to thalamus in 4 animals. Somatosensory evoked potentials (SSEPs) were recorded during peripheral stimulation after complete wound closure in multiple sessions up to 14-weeks after implant. For subdural arrays, mapping resulted in clearly separable clusters between peripheral stimulation sites. Decoding performance was quantified using a linear discriminant classification model that resulted in an overall accuracy of 0.96. Depth electrodes recorded SSEPs with latency between thalamus and cortex. Micro-stimulation at a single site with a 1 mA, 100-µsec biphasic pulse train of 50 pulses yielded large-scale network activity across the array which persists over several seconds, with an excitatory phase followed by inhibition before a return to baseline. Histopathology revealed mild microgliosis. CONCLUSIONS: A modular neural interface system consisting of fully implanted custom integrated circuit, customizable polyimide extender arrays, and wireless external power and telemetry can support high-resolution recording and micro-stimulation.