Towards maximizing optical access through Smart Dura

Objective.To overcome the limitations of optical access caused by opaque electrodes in multimodal neural interfaces used in large-animal models, and to enable scalable, high-density electrophysiology with unobstructed optical imaging and optogenetic stimulation.Approach.In this work, we redesigned our previously demonstrated multimodal cortical surface array, the Smart Dura, by incorporating transparent indium tin oxide (ITO) electrodes. ITO provides good electrical conductivity, while providing high levels of transparency. We discuss the design, microfabrication, benchtop characterization andin vivodemonstration of transparent Smart Dura for multimodal brain interfacing.In vivoexperiments were designed to show the feasibility of simultaneous electrophysiological recording with localized functional optical imaging through transparent Smart Dura in response to visual stimulation.Main results.The implementation of ITO electrodes increased the effective optical access of Smart Dura to 100%, eliminating obstruction from traditional metal electrodes. Bench-top characterization confirmed the electrical and optical performance of the transparent electrodes.In vivoresults demonstrate direct visual access underneath the ITO electrodes for optical recording and perturbation with co-located simultaneous high-fidelity electrophysiological recording, validating the multimodal capabilities of the transparent Smart Dura.Significance.The transparent Smart Dura design removes major barriers to optically integrated, high-density electrophysiology in large-animal models and the number and density of ITO electrodes on Smart Dura can be increased without compromising the optical access. This platform advances multimodal neural interfacing in non-human primates and provides unique opportunities to study brain function in health and disease and design therapeutics that can readily translate to humans.