Electrode failure: tissue, electrical, and material responses.

The development of invasive, rehabilitative neuroprosthetics for humans requires reliable neural probes that are capable of recording large ensembles of neurons for a long period of time. Recent advances in the development of neuroprosthetics in animals and humans have shown that communication and control can be directly derived from the central nervous system (CNS) for restoring lost motor ability. This proof of concept has opened the possibility of new therapies for the millions of individuals suffering from neurological disorders of the nervous system. The success of these therapies hinges on the ability to reliably access the relevant signals from the brain with high quality for the lifetime of the patient. As a result, research has focused on the cascade of events that follow chronic implantation of microelectrodes and temporal degradation in the signal and electrode quality: signal-to-noise ratio, noise floor, peak amplitude, and neuronal yield. Implanted microelectrodes have been reported to suffer from time-dependent degradation in signal quality due to unknown issues related to tissue interfaces.