Abstract

Abstract In neuroscience research and clinical practice, electrophysiology is used to record and stimulate specific parts of the brain with high temporal resolution. This capability can be augmented by magnetic resonance imaging (MRI), which provides anatomical and functional information about the brain with large spatial coverage. However, metallic electrodes, commonly used in electrophysiology, are fundamentally incompatible with MRI due to heating concerns and imaging artefacts. Here, it is demonstrated that flexible micro‐electrocorticography (µECoG) arrays, with electrodes made of poly(3,4‐ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS), are compatible with ultra‐high magnetic field MRI up to 9.4 T. A scalable fabrication process is adopted that results in very repeatable electrochemical properties across devices. The volumetric capacitance of PEDOT:PSS leads to low electrode impedance and enables high‐resolution neural recordings of single‐unit activity from the cortical surface of rodents. Furthermore, the µECoG array creates minimal distortion in T 2 ‐weighted anatomical brain MRI. Multimodal brain monitoring is demonstrated by performing simultaneous blood oxygen level‐dependent functional MRI (BOLD fMRI) in parallel with electrical stimulation from the µECoG array. The results show that the PEDOT:PSS µECoG arrays enable the combination of high‐resolution electrophysiology and advanced brain imaging in vivo.