Spatially controlled, bipolar, cortical stimulation with high-capacitance, mechanically flexible subdural surface microelectrode arrays.

Most neuromodulation approaches rely on extracellular electrical stimulation with penetrating electrodes at the cost of cortical damage. Surface electrodes, in contrast, are much less invasive but are challenged by the lack of proximity to axonal processes, leading to poor resolution. Here, we demonstrate that high-density (40-μm pitch), high-capacitance (>1 nF), single neuronal resolution PEDOT:PSS electrodes can be programmed to shape the charge injection front selectively at depths approaching 300 micrometers with a lateral resolution better than 100 micrometers. These electrodes, patterned on thin-film parylene substrate, can be subdurally implanted and adhere to the pial surface in chronic settings. By leveraging surface arrays that are optically transparent with PEDOT:PSS local interconnects and integrated with depth electrodes, we are able to combine surface stimulation and recording with calcium imaging and depth recording to demonstrate these spatial limits of bidirectional communication with pyramidal neurons in mouse visual cortex both laterally and at depth from the surface.