Neural-recording systems stimulators

Parylene s use in the medical field is linked to electronics. Certain pacemaker manufacturers use it as a protective conformal coating on pacemaker circuitry (69). The coated circuitry is sealed in a metal can, so that the parylene coating serves only as a backup should the primary barrier leak. There is also interest in its use as an electrode insulation in the fabrication of miniature electrodes for long-term implantation to record or to stimulate neurons in the central or peripheral nervous system, as the "front end" of experimental neural prostheses (70). One report describes the 3-yr survival of functioning parylene-coated electrodes in the brain of a monkey (71). 

By using tiny probes as neural prostheses, scientists may be able to restore nerve function in quadriplegics and make the blind see or the deaf hear. Thanks to advanced techniques, a single, small, implanted probe can stimulate individual neurons electrically or chemically and then record responses. Preliminary results suggest that the microprobe telemetry systems can be permanently implanted and replace damaged or missing nerves. 

If a microsystem should interface a regenerating nerve, some basic demands have to be taken into consideration the system must be absolutely non toxic, it must be stable in the physiologic environment for a long time, and the mechanical load on the severed nerve should be as minimal as possible during muscle contraction and limb movement. The neural prostheses should be equipped with multiple electrodes for recording nerve signals and for stimulation of different portions of the nerve. 

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. 

Micro electrode neural probes facilitate the functional stimulation or recording of neurons in the central nervous system and peripheral nervous system. Minimizing the electrode impedance is an important requirement for obtaining high quality signals (high signal-to-noise ratio). It has been shown [59,60] that... 

Chapter 1 discusses the implementation of improved cochlea implants. Such implants seeks provide aid to those who have suffered hearing loss, a problem which impacts over 36 million people. This work seeks to improve the process through which the implants are constructed, moving from wire-based systems to microfabricated electrode arrays, which provides highly localized stimulation and recording of the neural tissue. In addition to it, electronics and sensor integration enhances working performances with added functionality. 

If neural signals are to be used to control prostheses (Fig. 9.27), additional encoding between the technical and the biological system has to be done to transfer the information in an appropriate code. The sensor has to be placed inside the body to record signals that are used as command variables in the control task (Fig. 9.25c). One example for this adaptronic system is an implantable neural stimulator for grasp in paralyzed people with feedback response from an implanted sensor to control grasp force [18]. 

Polymer materials have been established as excellent materials in chemistry, automotives and electronics to interconnect different components, to electrically insulate conductors and to survive harsh corrosive environments. Polyimides are the most common material class for substrate and insulation materials in combination with metals for interconnection wires and electrode sites. Therefore, it is quite natural that the medical device industry has focused its attention to polyimides for medical devices in general and especially for encapsulation and insulation of active implants. Neural implants are technical systems that are mainly used to stimulate parts and structures of the nervous system with the aid of implanted electrical circuitry or record the electrical activity of nerve cells. Their application... 

Meyer RD, Cogan SF (2001) Electrodeposited iridium oxide for neural stimulation and recording electrodes. IEEE Trans Neural Syst Rehabil Eng 9(1) 2-10 Anderson DJ, Najafi K, Tanghe SJ, Evans DA, Levy KL, Hetke JF, Xue X, Zappia JJ, Wise KD (1989) Batch-fabricated thin-fllm electrodes for stimulation of the central auditory system. IEEE Trans Biomed Eng 36 693-704... 

Venkatraman S, Hendricks J, King Z, Sereno A, Richardson-Burns S, Martin D, Carmena J (2011) In vitro and in vivo evaluation of PEDOT microelectrodes for neural stimulation and recording. Neural Systems and Rehabilitation Engineering, IEEE Transactions on 19(3) 307-316, DOI 10.1109/TNSRE.2011.2109399... 

The physiological aspects of neural stimulation and recording such as the necessary characteristics of the signals for successful stimulation or the features of the neural signals to be read by the prosthetic system are not the main topic of this essay, although sometimes mentioned as support for the discussions, and should... 

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