Artifact-free, high-temporal-resolution in vivo opto-electrophysiology with microLED optoelectrodes

The combination of in vivo extracellular recording and genetic-engineering-assisted optical stimulation is a powerful tool for the study of neuronal circuits. Precise analysis of complex neural circuits requires high-density integration of multiple cellular-size light sources and recording electrodes. However, high-density integration inevitably introduces stimulation artifact. We present minimal-stimulation-artifact (miniSTAR) {micro}LED optoelectrodes that enable effective elimination of stimulation artifact. A multi-metal-layer structure with a shielding layer effectively suppresses capacitive coupling of stimulation signals. A heavily-boron-doped silicon substrate silences the photovoltaic effect induced from LED illumination. With transient stimulation pulse shaping, we reduced stimulation artifact on miniSTAR {micro}LED optoelectrodes to below 50 {micro}Vpp, much smaller than a typical spike detection threshold, at optical stimulation of > 50 mW mm-2 irradiance. We demonstrated high-temporal resolution (< 1 ms) opto-electrophysiology without any artifact-induced signal quality degradation during in vivo experiments. MiniSTAR {micro}LED optoelectrodes will facilitate functional mapping of local circuits and discoveries in the brain.