To achieve selective electrical interfacing to the neural system it is necessary to approach neuronal elements on a scale of micrometers. This necessitates microtechnology fabrication and introduces the interdisciplinary field of neurotechnology, lying at the juncture of neuroscience with microtechnology. The neuroelectronic interface occurs where the membrane of a cell soma or axon meets a metal microelectrode surface. The seal between these may be narrow or may be leaky. In the latter case the surrounding volume conductor becomes part of the interface. Electrode design for successful interfacing, either for stimulation or recording, requires good understanding of membrane phenomena, natural and evoked action potential generation, volume conduction, and electrode behavior. Penetrating multimicroelectrodes have been produced as one-, two-, and three-dimensional arrays, mainly in silicon, glass, and metal microtechnology. Cuff electrodes circumvent a nerve; their selectivity aims at fascicles more than at nerve fibers. Other types of electrodes are regenerating sieves and cone-ingrowth electrodes. The latter may play a role in brain-computer interfaces. Planar substrate-embedded electrode arrays with cultured neural cells on top are used to study the activity and plasticity of developing neural networks. They also serve as substrates for future so-called cultured probes.

Selective electrical interfaces with the nervous system.

Some embodiments of the present invention provide stimulation systems and components for selective stimulation and/or neuromodulation of one or more nerve root ganglia through implantation of an electrode on, in or around a nerve root ganglia. Some other embodiments of the present invention provide methods for selective neurostimulation of one or more dorsal root ganglia as well as techniques for applying neurostimulation to the spinal cord. Still other embodiments of the present invention provide stimulation systems and components for selective stimulation and/or neuromodulation of one or more nerve root ganglia through implantation of an electrode on, in or around a nerve root ganglia in combination with a pharmacological agent.

Methods for stimulating a nerve root ganglion

The paper reports on the deposition of iridium oxide thin films by dc reactive magnetron sputtering and their characterization by surface analysis methods (X-ray diffraction, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy) and electrochemical techniques (cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic square waves) The sputtering process was investigated by applying the method of generic curves An optimal combination of sputtering parameters has been established [40 standard cubic centimeters per minute (sccm) argon/8-12 sccm oxygen/40% effective pump power/100 W dc power/cold sputtering] that yields stable microporous amorphous films with a highly extended surface These films have shown an excellent electrochemical reversibility in physiological saline solution with a safe potential range of -12 to 13 V vs Ag/AgCl reference electrode, a charge delivery capacity of 90-95 mC/cm 2 , a constant impedance of 70-80 Ω in the frequency range of 100 kHz down to 05-10 Hz, and a quick response to bipolar current pulses with a safe charge per phase of 2 mC/cm 2 /ph The demonstrated remarkable electrochemical characteristics combined with their established long-term mechanical stability and corrosion resistance allow one to recommend the use of sputtered iridium oxide films as an ideal electrode material for neural stimulation

Sputtered Iridium Oxide Films as Charge Injection Material for Functional Electrostimulation

Publisher Summary This chapter discusses efforts from a number of groups that lay the groundwork for an in vitro approach to study the population coding. Most researchers studying population coding are working with intact, living animals. The cultured neuronal networks lack many features of real brains, but they retain many others. They develop organotypic synaptic connections and exhibit a rich variety of distributed patterns of electrical activity. Progress in multi-electrode array technology, optical recording, and multi-photon microscopy, made it possible that every cell in a cultured monolayer network can be observed, monitored, stimulated, and manipulated with temporal resolution in the sub millisecond range, and spatial resolution in the submicron range, in a non-destructive manner. The nascent field of population coding in networks of cultured neurons is poised for rapid expansion. Neural cell culture, long-term multi-electrode recording and stimulation, and multi-single-unit optical recording are now accessible to many labs. Computers are fast and cheap enough to allow real-time spike analysis and stimulus generation, which makes it possible to give cultured networks a simulated body to behave with, and an environment to interact with. By allowing the culture to behave and receive sensory input, meaning can be ascribed to the patterns of electrical activity it produces, and persistent changes in network activity can be thought of as learning.

Distributed processing in cultured neuronal networks.

Devices, systems and methods are provided for stimulation of tissues and structures within a body of a patient. In particular, implantable leads are provided which are comprised of a flexible circuit. Typically, the flexible circuit includes an array of conductors bonded to a thin dielectric film. Example dielectric films include polyimide, polyvinylidene fluoride (PVDF) or other biocompatible materials to name a few. Such leads are particularly suitable for stimulation of the spinal anatomy, more particularly suitable for stimulation of specific nerve anatomies, such as the dorsal root (optionally including the dorsal root ganglion).

F. Endres

Papers

Characterization and optimization of microelectrode arrays for in vivo nerve signal recording and stimulation