Transparent electrode for neural electrical stimulation and synchronized optical imaging

Transcranial electrical stimulation (TES) is widely used in treating brain disorders and enhancing cognitive functions. However, its effects and underlying neural mechanisms remain unclear, hindering further clinical development. This study introduces a novel transparent neural electrical stimulation (NES) electrode, paired with simultaneous in-situ two-photon calcium imaging, to investigate the effects and mechanisms of transcranial direct current stimulation. We developed an NES electrode with over 80% light transmittance in the visible spectrum and high electrical conductivity, utilizing micro-nano manufacturing technology and indium tin oxide, a transparent conductive material. This design ensures unobstructed optical interrogation and effective electrical stimulation. The electrode conforms snugly to the mouse cortex, efficiently delivering electric charges without degradation under varied polarization conditions (anodal and cathodal stimulations at 1.59 mA/cm² for 30 seconds across three trials), thereby maintaining consistent electrical and optical performance. Through this transparent electrode, we directly observed the effects of both anodal and cathodal direct current stimulation on neuronal activity in the cortex of an awake mouse. Due to the excellent transparency and electrical conductivity, the NES electrode can be combined with multiple optical brain imaging techniques to provide insights into the neural mechanisms and optimization strategies for treating brain disorders and enhancing cognitive functions using NES methods.