Neural prostheses

Implantable microelectronic devices for neural prosthesis require stimulation electrodes to have minimal electrochemical damage to tissue or nerve from chronic stimulation. Since most electrochemical reactions at the stimulation electrode surface alter the hydrogen ion concentration, one can expect a stimulus-induced pH shift [17]. When translated into a biological environment, these pH shifts could potentially have detrimental effects on the surrounding neural tissue and implant function. Measuring depth and spatial profiles of pH changes is important for the development of neural prostheses and safe stimulation protocols. 

The most welcome technical achievements in life science are the ones that enhance well-being or restore impaired or lost biological functions. Rehabilitation engineering is a research field that has devoted its full spectrum of efforts to compensate for malfunctions and disorders in human biological systems. This includes the development of devices for the rehabilitation of neural disorders which are termed neural prostheses. Neural prostheses directly interface with the central and peripheral nervous system. The most commonly known neural prosthesis is the cardiac pacemaker, which has existed for more than 30 years. A variety of other lesser known devices have been developed to partially restore neural functions in disabled people. 

A consortium of 13 technical and medical partners works on different tasks to develop a complete system for a visual prosthesis (Fig. 25). The neural pros-theses comprises a unit to record and process ambiance light, an encoder that transforms visual information into a sequence of stimulation pulses, a micro-electromechanical system that is implanted into the eye for interfacing the retina and for generating the appropriate stimuli. 

Pine J, Tai Y-C, Buzsaki G, Bragin A, Carpi D (1994) Quarterly Progress Report, NIH-NINDS, Neural Prosthesis Program No. 4, NOl-NS-3-2393... 

In the 1950s, a human study showing sound perception arising from electrode implantation inspired researchers across the world to investigate the possibility of a cochlear prosthesis, which, after several decades of development in academia and industry, became the hrst FDA approved neural prosthesis [17]. 

The Neural Prosthesis Program, launched in 1972 and spearheaded by F. Terry Hambrecht, MD, brought funding, focus, and coordination to the multidisciplinary effort to develop technologies to restore motor function in paralyzed individuals. The initial efforts were in electrode-tissue interaction, biomaterials and neural interface development, cochlear and visual prosthesis development and control of motor function using implanted and nonimplanted electrodes. 

Auditory prostheses, which provide patterned stimulation of the eighth cranial nerve, were the first commerdaUy available sensory neural prosthesis. As of this writing, it is the only approved sensory prosthesis however, visual prostheses are already in cHnical trials and are Hkely to be available in the not too distant future. 

Neural Prosthesis — Assistive systems for replacing or augmenting sensory-rootor fimcion Functional electrical stimulation or Functional neuromuscular stimulation Patterned electrical stimulation of neuromuscular structures dedicated to restore motor functions. 

Popovid D.B., Popovid M.B., Sinkjser T, Stefanovid A., and Schwirtlich L., Therapy of paretic arm in hemiplegic subjects augmented with a neural prosthesis a cross-over study. Can. J. Physio. 

Keller, T., Curt, A. et al.. Grasping in high lesioned tetraplegic subjects using the EMG controlled neural prosthesis,/. NeuroRehab. 10 251-255,1998. 

Popovid, M.R., Keller, T. et al.. Surface stimulation technology for grasping and walking neural prosthesis, lEEEEngng. Med. Biol. Mag. 20 82-93,2001. 

KeUer, T. and Popovid, M.R., Real-time stimulation artifact removal in EMG signals for neural prosthesis control appHcations. Proceedings of 6th Annual IFESS Conference, Cleveland, OH, June 10-13,... 

Kilgore, K.L., Peckham, P.H. et al.. An implanted upper-extremity neural prosthesis follow-up of five patients, /. Bone Joint Surg. Am. 79 533-541,1997. 

R.A. Green, L.A. Poole-Warren, and N.H. Lovell. Novel neural interface for vision prosthesis electrodes Improving electrical and mechanical properties through layering. In Proceedings of the 3rd International IEEE EMBS Conference on Neural Engineering, Kohala Coast, Hawaii, USA (2007). 

Assistive systems that apply FES to restore sensory or motor function are called neural prostheses. A neural prosthesis (NP) could improve sensory or motor function in subjects after cerebro-vascular accident (CVA), spinal cord injury (SCI), and some other diseases of the central nervous system (CNS) [1]. A motor NP applies electrical stimulation to artificially generate muscle contractions required for executing of a functional task in subjects who have lost voluntary control because of a disease or injury. The basic phenomena of the FES are the contraction of a muscle due to the direct stimulation... 

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