Progress in the field of micro-electrocorticography

Since the 1940s electrocorticography (ECoG) devices and, more recently, in the last decade, micro-electrocorticography (μECoG) cortical electrode arrays were used for a wide set of experimental and clinical applications, such as epilepsy localization and brain-computer interface (BCI) technologies. Miniaturized implantable μECoG devices have the advantage of providing greater-density neural signal acquisition and stimulation capabilities in a minimally invasive fashion. An increased spatial resolution of the μECoG array will be useful for greater specificity diagnosis and treatment of neuronal diseases and the advancement of basic neuroscience and BCI research. In this review, recent achievements of ECoG and μECoG are discussed. The electrode configurations and varying material choices used to design μECoG arrays are discussed, including advantages and disadvantages of μECoG technology compared to electroencephalography (EEG), ECoG, and intracortical electrode arrays. Electrode materials that are the primary focus include platinum, iridium oxide, poly(3,4-ethylenedioxythiophene) (PEDOT), indium tin oxide (ITO), and graphene. We discuss the biological immune response to μECoG devices compared to other electrode array types, the role of μECoG in clinical pathology, and brain-computer interface technology. The information presented in this review will be helpful to understand the current status, organize available knowledge, and guide future clinical and research applications of μECoG technologies.