Implantation of multi-electrode arrays is becoming increasingly more prevalent within the neuroscience research community. Many of these studies have been influenced by the recent interest from the NIH and other agencies toward the development of sensory and motor prosthesis. A motor prosthesis implant must record electrical activity from nearby neural elements, requiring a relatively passive electrode/tissue interface. A sensory prosthesis, however, must employ an electrode system, which can inject stimulus currents into the nervous system without damaging either nearby neural elements or the metal electrode. Both types of implants will require an electrode system that floats on the brain in order to minimize movement of the electrode tip, which can potentially damage nearby cells. Feedback from several neuroscience research groups have expressed the need for commercially available multi-electrode arrays that can penetrate into sub-cortical spaces sometimes extending 4 to 10 mm below the cortical surface. Other researchers have also suggested the need for electrode systems that will provide arrays with electrodes having different spacing and depths. There is also a relatively small, but growing, community of researchers, at this time, which must not only record from their electrode arrays but stimulate through them as well. A multi-electrode system that is biocompatible, electrically and mechanically stable, and employs design features allowing flexibility in the geometric layout and length of the individual electrodes within the array is needed in order to satisfy the multiple applications demanded by neuroscience researchers. An equally important component to the electrode fabrication and layout is the inclusion of remote electronics buried beneath the scalp capable of electro-magnetically transferring information across the scalp. This two- way communications between the outside world and the microelectrodes can be used for sensing electrical activity of nearby neural elements as control signals for a motor prosthesis or injecting currents into neural elements as part of a sensory prosthesis without the use of fragile wires and connector systems. Recent advances in laser machining of thin ceramic substrates, application of ultra-fine line gold conductors to ceramic, and the recent development of micro-circuit chips that can be bonded directly onto the ceramic substrate will provide the bases for the development of a Active Floating Multi-electrode Array. These arrays will be available as transcutaneous-wired ( AFMA), and wireless (WFMA) versions.
The development and commercialization of the """"""""Active Floating Micro-electrode Array"""""""", AFMA, will provide the neuroscience community with a new tool for stable long-term recording and stimulation protocols using a minimal 4-wire cable and head connector, regardless of the number of electrode channels needing to be serviced. The AFMA design is the next logical step in the development of a wireless transmission system that will eliminate unreliable head connectors and cables. The AFMA will form the basis for development of a wireless system (WFMA) capable of sending and receiving information to the implanted microelectrodes by means of wireless transmission through the skin and by RF transmission to nearby recording and stimulation control consoles. This new technology will provide an excellent tool for pre-clinical and eventual clinical trials associated with the development of motor and sensory prosthesis for people with paralysis and visual disorders respectively.
