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Annual International Conference of the... Jul 2023Large-scale network recording technology is critical in linking neural activity to behavior. Stable, long-term recordings collected from behaving animals are the...
Large-scale network recording technology is critical in linking neural activity to behavior. Stable, long-term recordings collected from behaving animals are the foundation for understanding neural dynamics and the plasticity of neural circuits. Penetrating microelectrode arrays (MEAs) can obtain high-resolution neural activity from different brain regions. However, ensuring the longevity of implantable devices and the consistency of neural signals over time remains one big challenge. A potential solution is to use flexible, polymer-based MEAs to minimize the foreign body response and prolong the lifetime of neural interfacing devices. Rodents and nonhuman primates (NHP) are commonly used animal models in neuroscience and neuroengineering studies. Specially designed MEAs that capture morphological features of different animal brains and various brain structures are powerful tools to simultaneously obtain neural activities from multiple brain regions. In this work, we develop a set of prototype designs of polymer MEAs that cover cortical, sub-cortical, and multiple brain regions of rodents and NHP.
Topics: Animals; Microelectrodes; Polymers; Electrodes, Implanted; Brain; Neurosciences
PubMed: 38083000
DOI: 10.1109/EMBC40787.2023.10340804 -
Molecules (Basel, Switzerland) Oct 2022Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1'-dimethanolferrocene and...
Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1'-dimethanolferrocene and potassium ferrocyanide. Electrochemical responses were examined after different oxidation treatments, then simulated and interpreted using the Kissa 1D software and existing models. Our experiments indicate that a crude carbon fiber behaves as an assembly of sites with different electrochemical reactivities. In such case, the Butler-Volmer law is not appropriate to describe the electron transfer kinetics because of the large created overpotential. Oxidation of the fiber erases the effect by increasing the kinetics of the electron transfer probably by a homogenization and increase of the reactivity on all the fiber. Additionally, analysis of the signal shows the large influence of the convection that affects the electrochemical response even at moderate scan rates (typically below 0.1-0.2 V s).
Topics: Carbon; Carbon Fiber; Electron Transport; Microelectrodes; Oxidation-Reduction
PubMed: 36235121
DOI: 10.3390/molecules27196584 -
Journal of Neural Engineering Feb 2020This paper aims to promote understanding on the fundamental concepts and mechanisms of extracellular electrical neural recording. (Review)
Review
OBJECTIVE
This paper aims to promote understanding on the fundamental concepts and mechanisms of extracellular electrical neural recording.
APPROACH
First, the electrode-electrolyte interface is reviewed to clarify some of the frequent misunderstandings. Second, analytical solutions to the extracellular field potential and recorded signal are derived based on equivalent electrical circuit models, using a planar substrate microelectrode as a particular example. And third, factors affecting the recording quality are thoroughly assessed.
MAIN RESULTS
Passive neural recording electrodes function as a pure capacitor. The extracellular field potential has two phases, with its subthreshold depolarization phase proportional to the first time derivative of the membrane depolarization and its action potential phase proportional to the negative first time derivative of the intracellular action potential. The recorded signal represents a portion of the extracellular field potential with both amplitude attenuation and phase distortion according to a voltage-divider circuit formed between the recording electrode and amplifier. A larger cell, a larger cell-substrate junctional membrane area, and a tighter membrane-substrate seal all help to improve the recording quality, while the effective electrode impedance should be minimized and the effective amplifier's input impedance maximized.
SIGNIFICANCE
This paper develops in-depth insights to offer a clear image on the recording mechanism, nature of the signal, and interplays between key interface parameters. This work will make a foundational contribution to the field by providing such an in-depth understanding on this topic to clear the widespread ambiguities and confusions and inform rational neural electrode designs and proper interpretations of neural recordings.
Topics: Animals; Electric Impedance; Electrodes, Implanted; Electrolytes; Humans; Microelectrodes; Neurons
PubMed: 31986493
DOI: 10.1088/1741-2552/ab702f -
Advanced Healthcare Materials Jun 2021To understand the physiology and pathology of electrogenic cells and the corresponding tissue in their full complexity, the quantitative investigation of the... (Review)
Review
To understand the physiology and pathology of electrogenic cells and the corresponding tissue in their full complexity, the quantitative investigation of the transmission of ions as well as the release of chemical signals is important. Organic (semi-) conducting materials and in particular organic electrochemical transistor are gaining in importance for the investigation of electrophysiological and recently biochemical signals due to their synthetic nature and thus chemical diversity and modifiability, their biocompatible and compliant properties, as well as their mixed electronic and ionic conductivity featuring ion-to-electron conversion. Here, the aim is to summarize recent progress on the development of bioelectronic devices utilizing polymer polyethylenedioxythiophene: poly(styrene sulfonate) (PEDOT:PSS) to interface electronics and biological matter including microelectrode arrays, neural cuff electrodes, organic electrochemical transistors, PEDOT:PSS-based biosensors, and organic electronic ion pumps. Finally, progress in the material development is summarized for the improvement of polymer conductivity, stretchability, higher transistor transconductance, or to extend their field of application such as cation sensing or metabolite recognition. This survey of recent trends in PEDOT:PSS electrophysiological sensors highlights the potential of this multifunctional material to revolve current technology and to enable long-lasting, multichannel polymer probes for simultaneous recordings of electrophysiological and biochemical signals from electrogenic cells.
Topics: Bridged Bicyclo Compounds, Heterocyclic; Electric Conductivity; Microelectrodes; Polymers
PubMed: 33970552
DOI: 10.1002/adhm.202100061 -
Biosensors Feb 2023Electrical impedance spectroscopy (EIS) is widely recognized as a powerful tool in biomedical research. For example, it allows detection and monitoring of diseases,...
Electrical impedance spectroscopy (EIS) is widely recognized as a powerful tool in biomedical research. For example, it allows detection and monitoring of diseases, measuring of cell density in bioreactors, and characterizing the permeability of tight junctions in barrier-forming tissue models. However, with single-channel measurement systems, only integral information is obtained without spatial resolution. Here we present a low-cost multichannel impedance measurement set-up capable of mapping cell distributions in a fluidic environment by using a microelectrode array (MEA) realized in 4-level printed circuit board (PCB) technology including layers for shielding, interconnections, and microelectrodes. The array of 8 × 8 gold microelectrode pairs was connected to home-built electric circuitry consisting of commercial components such as programmable multiplexers and an analog front-end module which allows the acquisition and processing of electrical impedances. For a proof-of-concept, the MEA was wetted in a 3D printed reservoir into which yeast cells were locally injected. Impedance maps were recorded at 200 kHz which correlate well with the optical images showing the yeast cell distribution in the reservoir. Blurring from parasitic currents slightly disturbing the impedance maps could be eliminated by deconvolution using an experimentally determined point spread function. The MEA of the impedance camera can in future be further miniaturized and integrated into cell cultivation and perfusion systems such as organ on chip devices to augment or even replace light microscopic monitoring of cell monolayer confluence and integrity during the cultivation in incubation chambers.
Topics: Electric Impedance; Saccharomyces cerevisiae; Microscopy; Gold; Microelectrodes
PubMed: 36832047
DOI: 10.3390/bios13020281 -
Journal of Neural Engineering Apr 2023. Spike sorting is a set of techniques used to analyze extracellular neural recordings, attributing individual spikes to individual neurons. This field has gained... (Review)
Review
. Spike sorting is a set of techniques used to analyze extracellular neural recordings, attributing individual spikes to individual neurons. This field has gained significant interest in neuroscience due to advances in implantable microelectrode arrays, capable of recording thousands of neurons simultaneously. High-density electrodes, combined with efficient and accurate spike sorting systems, are essential for various applications, including brain machine interfaces (BMIs), experimental neural prosthetics, real-time neurological disorder monitoring, and neuroscience research. However, given the resource constraints of modern applications, relying solely on algorithmic innovation is not enough. Instead, a co-optimization approach that combines hardware and spike sorting algorithms must be taken to develop neural recording systems suitable for resource-constrained environments, such as wearable devices and BMIs. This co-design requires careful consideration when selecting appropriate spike-sorting algorithms that match specific hardware and use cases.. We investigated the recent literature on spike sorting, both in terms of hardware advancements and algorithms innovations. Moreover, we dedicated special attention to identifying suitable algorithm-hardware combinations, and their respective real-world applicabilities.. In this review, we first examined the current progress in algorithms, and described the recent departure from the conventional '3-step' algorithms in favor of more advanced template matching or machine-learning-based techniques. Next, we explored innovative hardware options, including application-specific integrated circuits, field-programmable gate arrays, and in-memory computing devices (IMCs). Additionally, the challenges and future opportunities for spike sorting are discussed.. This comprehensive review systematically summarizes the latest spike sorting techniques and demonstrates how they enable researchers to overcome traditional obstacles and unlock novel applications. Our goal is for this work to serve as a roadmap for future researchers seeking to identify the most appropriate spike sorting implementations for various experimental settings. By doing so, we aim to facilitate the advancement of this exciting field and promote the development of innovative solutions that drive progress in neural engineering research.
Topics: Signal Processing, Computer-Assisted; Action Potentials; Algorithms; Computers; Microelectrodes; Models, Neurological
PubMed: 36972585
DOI: 10.1088/1741-2552/acc7cc -
Journal of Neural Engineering Aug 2019Various retinal prostheses have been developed to restore the vision for blind patients, and some of them are already in clinical use. In this paper, we present a...
OBJECTIVE
Various retinal prostheses have been developed to restore the vision for blind patients, and some of them are already in clinical use. In this paper, we present a three-dimensional (3D) microelectrode array for a subretinal device that can effectively stimulate retinal cells.
APPROACH
To investigate the effect of electrode designs on the electric field distribution, we simulated various electrode shapes and sizes using finite element analysis. Based on the simulation results, the 3D microelectrode array was fabricated and evaluated in in vitro condition.
MAIN RESULTS
Through the simulation, we verified that an electrode design of square frustum was effective to stimulate with high contrast. Also, the 3D flexible and transparent microelectrode array based on silicon and polydimethylsiloxane was fabricated using micro-electro-mechanical system technologies. In in vitro experiments, the subretinally positioned 3D microelectrodes properly evoked spikes in retinal ganglion cells. The mean threshold current was 7.4 µA and the threshold charge density was 33.64 µC·cm per phase.
SIGNIFICANCE
The results demonstrate the feasibility of the fabricated 3D microelectrodes as the subretinal prosthesis. The developed microelectrode array would be integrated with the stimulation circuitry and implanted in animals for further in vivo experiments.
Topics: Animals; Electrodes, Implanted; Equipment Design; Evoked Potentials, Visual; Mice; Mice, Inbred C57BL; Microelectrodes; Pliability; Retina; Retinal Ganglion Cells; Visual Prosthesis
PubMed: 31357188
DOI: 10.1088/1741-2552/ab36ab -
Acta Biomaterialia Aug 2023Intracortical microelectrodes induce vascular injury upon insertion into the cortex. As blood vessels rupture, blood proteins and blood-derived cells (including...
Intracortical microelectrodes induce vascular injury upon insertion into the cortex. As blood vessels rupture, blood proteins and blood-derived cells (including platelets) are introduced into the 'immune privileged' brain tissues at higher-than-normal levels, passing through the damaged blood-brain barrier. Blood proteins adhere to implant surfaces, increasing the likelihood of cellular recognition leading to activation of immune and inflammatory cells. Persistent neuroinflammation is a major contributing factor to declining microelectrode recording performance. We investigated the spatial and temporal relationship of blood proteins fibrinogen and von Willebrand Factor (vWF), platelets, and type IV collagen, in relation to glial scarring markers for microglia and astrocytes following implantation of non-functional multi-shank silicon microelectrode probes into rats. Together with type IV collagen, fibrinogen and vWF augment platelet recruitment, activation, and aggregation. Our main results indicate blood proteins participating in hemostasis (fibrinogen and vWF) persisted at the microelectrode interface for up to 8-weeks after implantation. Further, type IV collagen and platelets surrounded the probe interface with similar spatial and temporal trends as vWF and fibrinogen. In addition to prolonged blood-brain barrier instability, specific blood and extracellular matrix proteins may play a role in promoting the inflammatory activation of platelets and recruitment to the microelectrode interface. STATEMENT OF SIGNIFICANCE: Implanted microelectrodes have substantial potential for restoring function to people with paralysis and amputation by providing signals that feed into natural control algorithms that drive prosthetic devices. Unfortunately, these microelectrodes do not display robust performance over time. Persistent neuroinflammation is widely thought to be a primary contributor to the devices' progressive decline in performance. Our manuscript reports on the highly local and persistent accumulation of platelets and hemostatic blood proteins around the microelectrode interface of brain implants. To our knowledge neuroinflammation driven by cellular and non-cellular responses associated with hemostasis and coagulation has not been rigorously quantified elsewhere. Our findings identify potential targets for therapeutic intervention and a better understanding of the driving mechanisms to neuroinflammation in the brain.
Topics: Rats; Animals; Blood Platelets; Microelectrodes; Hemostatics; von Willebrand Factor; Neuroinflammatory Diseases; Collagen Type IV; Electrodes, Implanted; Hemostasis; Fibrinogen
PubMed: 37211307
DOI: 10.1016/j.actbio.2023.05.004 -
Neuromodulation : Journal of the... Aug 2022One of the main challenges posed by the surgical deep brain stimulation (DBS) procedure is the successful targeting of the structures of interest and avoidance of side...
OBJECTIVES
One of the main challenges posed by the surgical deep brain stimulation (DBS) procedure is the successful targeting of the structures of interest and avoidance of side effects, especially in asleep surgery. Here, intraoperative motor evoked potentials (MEPs) might serve as tool to identify the pyramidal tract. We hypothesized that intraoperative MEPs are useful to define the distance to the pyramidal tract and reduce the occurrence of postoperative capsular side effects.
MATERIALS AND METHODS
Motor potentials were evoked through both microelectrode and DBS-electrode stimulation during stereotactic DBS surgery on 25 subthalamic nuclei and 3 ventral intermediate thalamic nuclei. Internal capsule proximity was calculated for contacts on microelectrode trajectories, as well as for DBS-electrodes, and correlated with the corresponding MEP thresholds. Moreover, the predictivity of intraoperative MEP thresholds on the probability of postoperative capsular side effects was calculated.
RESULTS
Intraoperative MEPs thresholds correlated significantly with internal capsule proximity, regardless of the stimulation source. Furthermore, MEPs thresholds were highly accurate to exclude the occurrence of postoperative capsular side effects.
CONCLUSIONS
Intraoperative MEPs provide additional targeting guidance, especially in asleep DBS surgery, where clinical value of microelectrode recordings and test stimulation may be limited. As this technique can exclude future capsular side effects, it can directly be translated into clinical practice.
Topics: Deep Brain Stimulation; Evoked Potentials, Motor; Humans; Microelectrodes; Pyramidal Tracts; Subthalamic Nucleus
PubMed: 33779014
DOI: 10.1111/ner.13386 -
ACS Applied Bio Materials Sep 2023The learning and memory functions of the brain remain unclear, which are in urgent need for the detection of both a single cell signal with high spatiotemporal... (Review)
Review
The learning and memory functions of the brain remain unclear, which are in urgent need for the detection of both a single cell signal with high spatiotemporal resolution and network activities with high throughput. Here, an in vitro microelectrode array (MEA) was fabricated and further modified with polypyrrole/carboxylated single-walled carbon nanotubes (PPy/SWCNTs) nanocomposites as the interface between biological and electronic systems. The deposition of the nanocomposites significantly improved the performance of microelectrodes including low impedance (60.3 ± 28.8 k Ω), small phase delay (-32.8 ± 4.4°), and good biocompatibility. Then the modified MEA was used to apply learning training and test on hippocampal neuronal network cultured for 21 days through electrical stimulation, and multichannel electrophysiological signals were recorded simultaneously. During the process of learning training, the stimulus/response ratio of the hippocampal learning population gradually increased and the response time gradually decreased. After training, the mean spikes in burst, number of bursts, and mean burst duration increased by 53%, 191%, and 52%, respectively, and the correlation of neurons in the network was significantly enhanced from 0.45 ± 0.002 to 0.78 ± 0.002. In addition, the neuronal network basically retained these characteristics for at least 5 h. These results indicated that we have successfully constructed a learning and memory model of hippocampal neurons on the in vitro MEA, contributing to understanding learning and memory based on synaptic plasticity. The proposed PPy/SWCNTs-modified in vitro MEA will provide a promising platform for the exploration of learning and memory mechanism and their applications in vitro.
Topics: Microelectrodes; Polymers; Nanotubes, Carbon; Pyrroles; Neurons; Electric Stimulation; Hippocampus
PubMed: 37071831
DOI: 10.1021/acsabm.3c00105