Constant-current adjustable-waveform microstimulator for an implantable hybrid neural prosthesis.

Microstimulation of neural tissue has become a widely-used technique for controlling neuronal responses with local electric fields as well as a therapeutic intervention for nervous system disorders such as epilepsy and Parkinson's disease. Of those afflicted by neurological diseases, many are or become tolerant to existing pharmaceuticals and are left with little recourse. Little is known about the necessary design criteria or efficacy of a hybrid neural prosthesis. Assessment of the potential clinical value of a hybrid electro-chemical neural prosthesis was performed through in vitro verification using a prototype microstimulator and P19 cell cultures. We constructed a printed circuit board (PCB) microstimulator as a prototype of a CMOS microstimulator ASIC that was subsequently fabricated in the IBM 7RF 0.18 microm process. Measured results for the prototype are described in this work. An output impedance of 237 kOmega, voltage compliance of 11.3 V, and a linear constant-current output up to +/-600 microA make this microstimulator system a viable option for an implantable hybrid neural prosthesis. Hybrid prostheses could uniquely affect neural modulation with linear glutamate release at physiological amplitudes and frequencies.