Microelectronics and neural prostheses

The realization of effective neural prostheses requires both understanding of the neural physiological substrate of the function and the availability of hardware, stimulation electronics, electrodes, sensors, and information processing electronics, to execute the required function. Microelectronics, especially custom and semicustom integrated circuits, have effectively removed some of these barriers. Particularly in the area of implantable stimulation electronics, custom integrated circuits and advanced hermetic packaging techniques have been developed so that it is possible to make very small, long-lived multichannel stimulation systems. Similarly, the availability of low-power CMOS microprocessors, logic and memory components makes it possible to execute complex information processing in small, low-power portable systems. The principal technological bottlenecks in neural prostheses remain stimulation electrodes and physiological sensors. The techniques underlying microelectronic photolithographic fabrication may also make possible the “solution” of the electrode and sensor problems. In our auditory prosthesis project, we have photolithographic electrode arrays of both rigid and flexible character now nearing operational status. These electrodes are probably generalizable to a fairly wide number of prostheses applications. A number of sensors, especially those of pressure, motion and temperature, are also yielding to photolithographic fabrication. The sensor problem, however, for such physiologic parameters as ionic concentration remains the most difficult to conquer. Examples and illustrations of the state-of-the-art in these areas, as achieved by microelectronic techniques, will be given.