NEXT GENERATION OF CORTICAL DEVICES

Much of our understanding of brain function and organization has been provided via the single microelectrode. Single microelectrode studies of sensory and motor processing in the brain have also inspired the development of neuroprosthetic approaches that someday may aid the deaf, blind, or paralyzed. Necessarily complex, such approaches will require sophisticated multi-electrode arrays implanted into one or more regions of the brain. Today, devices available for implantation into the brain have multiple electrode sites, are chronically implantable, and can include circuitry for on-board signal processing. The utility of multi-electrode arrays to either electrically stimulate or record within the brain has been well-demonstrated in basic research animal studies. However, such devices are not yet regularly incorporated in the clinical arena. Although the complex neural interfaces available today are impressive, they have yet to demonstrate the necessary longevity required or to meet the other stringent requirements for human implantation. Only when electrode systems can be made to function reliably and consistently for the lifetime of an implanted subject will these gains be possible. In this chapter, a brief review of known and postulated failure modes and device limitations are presented in an effort to define a working plan for the development of more effective devices in the future. This plan incorporates the best of currently available neural engineering technologies with new and as of yet undeveloped advances. By understanding the failure modes of previous systems and anticipating the requirements of advanced systems, a plan for development of the next generation of cortical implants can be outlined.