scholarly journals Predicting neural recording performance of implantable electrodes

The Analyst ◽  
2019 ◽  
Vol 144 (9) ◽  
pp. 2973-2983 ◽  
Author(s):  
Alexander R. Harris ◽  
Ben J. Allitt ◽  
Antonio G. Paolini
Keyword(s):  
Neural Recording ◽  
Electrode Impedance ◽  
Low Frequencies ◽  
Implantable Electrodes

Electrode impedance at low frequencies was a stronger predictor of electrophysiological performance than the typically reported impedance at 1 kHz.

Graphene-based implantable electrodes for neural recording/stimulation

2021 ◽  
Author(s):  
Sara Khademi ◽  
Md Eshrat E Alahi ◽  
Kamran Foroutani
Keyword(s):  
Neural Recording ◽  
Implantable Electrodes

scholarly journals Creating Low-Impedance Coatings for Neural Recording Electrodes Using Electroplating Inhibitors

2009 ◽  
Vol 3 (2) ◽  
Author(s):  
J. E. Ferguson ◽  
C. Boldt ◽  
A. D. Redish
Keyword(s):  
Carbon Nanotubes ◽  
Neural Recording ◽  
Electrode Impedance ◽  
Gold Plating ◽  
Sem Image ◽  
Nano Scale ◽  
Multi Walled Carbon Nanotubes ◽  
Plating Solution ◽  
Walled Carbon Nanotubes

Microelectrodes are routinely used for recording from ensembles of neurons for clinical and neuroscience research applications. The quality of the neural recording is highly dependant on the electrical properties of the microelectrode. Lowering the impedance of the electrode-electrolyte interface can improve the signal-to-noise ratio and the ability of the microelectrode to record from more distant neurons. Therefore, tetrodes, which are made by twisting four 12.7 μm nichrome wires together, are usually gold plated to lower impedances to 200–500 kΩ (measured at 1 kHz) before implantation. A further reduction in impedance could drastically improve recording quality but is not possible with standard gold electroplating methods without causing crossed connections (shorts) between the wires. Keefer et al. (2008, Nature Nanotechnology) reported that they could reduce electrode impedance and improve neural recordings by adding multi-walled carbon nanotubes to the gold plating solution, producing a “rice-like” texture on electrode coatings. We replicated this coating and were able to lower tetrode impedances to 120–150 kΩ without crossed connections. Furthermore, we found that by decreasing the electroplating current density and the concentration of multi-walled carbon nanotubes in the gold plating solution, we could create a 40–90 kΩ coating on each tetrode wire without any crossed connections. A scanning electron microscope (SEM) image revealed this 40–90 kΩ coating to be thick and globular with nano-scale texture, distinct from the “rice-like” coating of Keefer et al. The nano-scale texture coating had a large effective surface area likely responsible for the great reduction in impedance. In comparison, an SEM image of a standard gold-plated tetrode showed a thin coating with primarily lateral growth. The carbon nanotubes act as electroplating inhibitors by adsorbing onto the electrode surface and changing the dynamics of the gold electrocrystallization. We confirmed this by replacing the carbon nanotubes with polyethylene glycol (PEG), a known electroplating inhibitor, recreating the nano-scale texture and 40–90 kΩ tetrode impedances. By varying the concentration of electroplating inhibitors and the electroplating current, the dynamics of gold electrocrystallization can be controlled. This gives the ability to design an electrode coating with a specific shape, thickness, and texture that can be tailored to a specific application. Creating a low-impedance coating with a nano-scale texture using electroplating inhibitors can improve the recording quality of microelectrodes and can allow for the use of smaller microelectrodes that were previously limited by their high impedance. Supported by a grant from the Institute for Engineering in Medicine (U Minnesota) and training grant support from T32-EB008389. Corresponding author; email: [email protected]

Characterization of Degradation Mechanisms in Neural Recording Electrodes

2007 ◽  
Vol 1009 ◽  
Author(s):  
Jennifer M. Anton ◽  
Stephanie A. Hooker
Keyword(s):  
Neural Activity ◽  
Neural Recording ◽  
Electrode Impedance ◽  
Implanted Electrodes ◽  
Recording Process ◽  
Primary Measurement ◽  
Freely Behaving ◽  
Signal Recording

Understanding the nature of specific neural activity is essential to the progression of research in the field of brain disorders and diseases, as well as neuroprosthetics. Microelectrodes are the primary measurement devices used to transduce neural activity into electrical signals to help neuroscientists study dynamic brain function. Advances in signal processing and packaging currently allow neural recording for periods as long as a year by use of chronically implanted electrodes in freely behaving animals. Stability of the electrode impedance is required for optimum signal recording over the length of the recording interval. While electrode–tissue interaction plays a major role in the quality of the recorded signal, delamination or degradation of the dielectric coating also interferes with signal recording. Therefore, to improve the signal recording process, it is useful to understand how the electrode design and component materials affect the signal over the course of time.

scholarly journals A new system for measuring electrical conductivity of water as a function of admittance

2019 ◽  
Vol 2 (1) ◽  
pp. 86-92 ◽  
Author(s):  
Haval Y. Yacoob Aldosky ◽  
Suzan M. H. Shamdeen
Keyword(s):  
Tap Water ◽  
Water Sources ◽  
Electrode System ◽  
Electrode Impedance ◽  
Water Conductivity ◽  
Plastic Tube ◽  
Low Frequencies ◽  
Good Operation ◽  
New System ◽  
Four Electrodes

Abstract This paper presents a new system for measuring water conductivity as a function of electrophysical property (admittance). The system is cheap and its manufacturing is easy. In addition, it does not require any sort of electrolysis and calibration. The system consists of four electrodes made of silver (Ag 92.5 g to Cu 7.5 g) fixed in a plastic tube filled by water which allows the use of two and four electrode setups. The admittance (reciprocal of impedance) was measured for different water sources (distilled, rainfall, mineral, river and tap water) using different frequencies between 50 Hz and 100 kHz. These measurements were taken twice, first with four electrodes and then with two electrodes of two modes (inner and outer electrodes). The results showed good correlation between the measured admittance and the conductivity of all the water sources and the best correlation was found at low frequencies between 50 Hz and 20 kHz. The highest efficiency can be achieved by using the four electrode system which allows circumventing the effect of the electrode impedance. This result makes the system efficient compared to traditional conductivity meters which usually require high frequencies for good operation.

Impedance spectroscopy of (TlGaSe2)1−x(TlInSe2)x solid solutions in radio frequency range

2020 ◽  
Vol 34 (11) ◽  
pp. 2050113
Author(s):  
R. M. Sardarli ◽  
F. T. Salmanov ◽  
N. A. Alieva ◽  
R. M. Abbasli
Keyword(s):  
Charge Transfer ◽  
Impedance Spectroscopy ◽  
Electric Fields ◽  
Solid Solutions ◽  
Effective Medium Theory ◽  
Low Frequency ◽  
Localized States ◽  
Electrode Impedance ◽  
Frequency Range ◽  
Low Frequencies

The processes of charge transport on alternating current in [Formula: see text] solid solutions have been studied. It has been established that in weak alternating electric fields, there is a hopping mechanism of charge transfer over localized states in the vicinity of the Fermi level. A quantitative assessment of parameters was made in the framework of the effective medium theory and the Mott approximation. The use of impedance spectroscopy methods in [Formula: see text] solid solutions in the frequency range of 25–106 Hz, at temperatures of 180, 240 and 300 K charge transfer processes has been investigated. It was found that at 300 K in the low-frequency region, there are additional contributions to the conductivity, which, apparently, is associated with diffuse ion transfer near the boundary of the solid electrolyte and the electrode. Impedance locus curves, at low frequencies and at a temperature of 300 K, are characteristic of Warburg diffuse impedance.

The S-SH Confusion Test and the Effects of Frequency Lowering

2019 ◽  
Vol 62 (5) ◽  
pp. 1486-1505
Author(s):  
Joshua M. Alexander
Keyword(s):  
Cognitive Processing ◽  
Hearing Aids ◽  
Response Times ◽  
Nonlinear Frequency ◽  
Low Frequencies ◽  
Frequency Compression ◽  
Negative Side ◽  
Minimal Word ◽  
Low Pass ◽  
Negative Side Effects

PurposeFrequency lowering in hearing aids can cause listeners to perceive [s] as [ʃ]. The S-SH Confusion Test, which consists of 66 minimal word pairs spoken by 6 female talkers, was designed to help clinicians and researchers document these negative side effects. This study's purpose was to use this new test to evaluate the hypothesis that these confusions will increase to the extent that low frequencies are altered.MethodTwenty-one listeners with normal hearing were each tested on 7 conditions. Three were control conditions that were low-pass filtered at 3.3, 5.0, and 9.1 kHz. Four conditions were processed with nonlinear frequency compression (NFC): 2 had a 3.3-kHz maximum audible output frequency (MAOF), with a start frequency (SF) of 1.6 or 2.2 kHz; 2 had a 5.0-kHz MAOF, with an SF of 1.6 or 4.0 kHz. Listeners' responses were analyzed using concepts from signal detection theory. Response times were also collected as a measure of cognitive processing.ResultsOverall, [s] for [ʃ] confusions were minimal. As predicted, [ʃ] for [s] confusions increased for NFC conditions with a lower versus higher MAOF and with a lower versus higher SF. Response times for trials with correct [s] responses were shortest for the 9.1-kHz control and increased for the 5.0- and 3.3-kHz controls. NFC response times were also significantly longer as MAOF and SF decreased. The NFC condition with the highest MAOF and SF had statistically shorter response times than its control condition, indicating that, under some circumstances, NFC may ease cognitive processing.ConclusionsLarge differences in the S-SH Confusion Test across frequency-lowering conditions show that it can be used to document a major negative side effect associated with frequency lowering. Smaller but significant differences in response times for correct [s] trials indicate that NFC can help or hinder cognitive processing, depending on its settings.

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