CMOS-based Microelectrode Array Research Articles

Avoidance of axonal stimulation with sinusoidal epiretinal stimulation

Objective. Neuromodulation, particularly electrical stimulation, necessitates high spatial resolution to achieve artificial vision with high acuity. In epiretinal implants, this is hindered by the undesired activation of distal axons. Here, we investigate focal and axonal activation of retinal ganglion cells (RGCs) in epiretinal configuration for different sinusoidal stimulation frequencies. Approach. RGC responses to epiretinal sinusoidal stimulation at frequencies between 40 and 100 Hz were tested in ex-vivo photoreceptor degenerated (rd10) isolated retinae. Experiments were conducted using a high-density CMOS-based microelectrode array, which allows to localize RGC cell bodies and axons at high spatial resolution. Main results. We report current and charge density thresholds for focal and distal axon activation at stimulation frequencies of 40, 60, 80, and 100 Hz for an electrode size with an effective area of 0.01 mm2. Activation of distal axons is avoided up to a stimulation amplitude of 0.23 µA (corresponding to 17.3 µC cm−2) at 40 Hz and up to a stimulation amplitude of 0.28 µA (14.8 µC cm−2) at 60 Hz. The threshold ratio between focal and axonal activation increases from 1.1 for 100 Hz up to 1.6 for 60 Hz, while at 40 Hz stimulation frequency, almost no axonal responses were detected in the tested intensity range. With the use of synaptic blockers, we demonstrate the underlying direct activation mechanism of the ganglion cells. Finally, using high-resolution electrical imaging and label-free electrophysiological axon tracking, we demonstrate the extent of activation in axon bundles. Significance. Our results can be exploited to define a spatially selective stimulation strategy avoiding axonal activation in future retinal implants, thereby solving one of the major limitations of artificial vision. The results may be extended to other fields of neuroprosthetics to achieve selective focal electrical stimulation.

Stability of cell adhesion noise analysis for the detection of cancer cell lines

Abstract Detecting cells on substrates time-continuously without the need of optical microscopy is broad interest in biotechnological applications. We demonstrate the stability and repeatability of a method to detect cancer cells using cell adhesion noise spectroscopy across different CMOS-based microelectrode arrays. We analyze the recordings in terms of spectral power density.

Electrical imaging of axonal stimulation in the retina

Abstract Stimulation of axons or its avoidance plays a central role for neuroprosthetics and neural-interfaces research. One peculiar example constitutes retinal implants. Retinal implants aim to artificially activate retinal ganglion cells (RGCs) via electrical stimulation. Such stimulation, however, often generates undesired stimulation of RGC axon bundles, which leads to distorted visual percepts. In order to establish stimulation strategies avoiding axonal stimulation it is necessary to image the evoked activity in single axons. In this work we electrically imaged axonal stimulation in ex vivo mouse retina using a high-density CMOS-based microelectrode array. We demonstrate signal propagation tracking via stimulus triggered average during high frequency (100 Hz) sinusoidal electrical stimulation.

Spatial and temporal resolution of optogenetically recovered vision in ChR2-transduced mouse retina

Objective. Retinal ganglion cells (RGCs) represent an attractive target in vision restoration strategies, because they undergo little degeneration compared to other retinal neurons. Here we investigated the temporal and spatial resolution in adult photoreceptor-degenerated (rd10) mouse retinas, where RGCs have been transduced with the optogenetic actuator channelrhodopsin-2 (ChR2). Approach. The RGC spiking activity was recorded continuously with a CMOS-based microelectrode array during a variety of photostimulation protocols. The temporal resolution was assessed through Gaussian white noise stimuli and evaluated using a linear-nonlinear-Poisson model. Spatial sensitivity was assessed upon photostimulation with single rectangular pulses stepped across the retina and upon stimulation with alternating gratings of different spatial frequencies. Spatial sensitivity was estimated using logistic regression or by evaluating the spiking activity of independent RGCs. Main results. The temporal resolution after photostimulation displayed an about ten times faster kinetics as compared to physiological filters in wild-type RGCs. The optimal spatial resolution estimated using the logistic regression model was 10 µm and 87 µm based on the population response. These values correspond to an equivalent acuity of 1.7 or 0.2 cycles per degree, which is better than expected from the size of RGCs’ optogenetic receptive fields. Significance. The high temporal and spatial resolution obtained by photostimulation of optogenetically transduced RGCs indicate that high acuity vision restoration may be obtained by photostimulation of appropriately modified RGCs in photoreceptor-degenerated retinas.

Human Cerebrospinal Fluid Induces Neuronal Excitability Changes in Resected Human Neocortical and Hippocampal Brain Slices.

Human cerebrospinal fluid (hCSF) has proven advantageous over conventional medium for culturing both rodent and human brain tissue. In addition, increased activity and synchrony, closer to the dynamic states exclusively recorded in vivo, were reported in rodent slices and cell cultures switching from artificial cerebrospinal fluid (aCSF) to hCSF. This indicates that hCSF possesses properties that are not matched by the aCSF, which is generally used for most electrophysiological recordings. To evaluate the possible significance of using hCSF as an electrophysiological recording medium, also for human brain tissue, we compared the network and single-cell firing properties of human brain slice cultures during perfusion with hCSF and aCSF. For measuring the overall activity from a majority of neurons within neocortical and hippocampal human slices, we used a microelectrode array (MEA) recording technique with 252 electrodes covering an area of 3.2 × 3.2 mm2. A second CMOS-based MEA with 4225 sensors on a 2 × 2 mm2 area was used for detailed mapping of action potential waveforms and cell identification. We found that hCSF increased the number of active electrodes and neurons and the firing rate of the neurons in the slices and induced an increase in the numbers of single channel and population bursts. Interestingly, not only an increase in the overall activity in the slices was observed, but a reconfiguration of the network could also be detected with specific activation and inactivation of subpopulations of neuronal ensembles. In conclusion, hCSF is an important component to consider for future human brain slice studies, especially for experiments designed to mimic parts of physiology and disease observed in vivo.

Probing and predicting ganglion cell responses to smooth electrical stimulation in healthy and blind mouse retina

Retinal implants are used to replace lost photoreceptors in blind patients suffering from retinopathies such as retinitis pigmentosa. Patients wearing implants regain some rudimentary visual function. However, it is severely limited compared to normal vision because non-physiological stimulation strategies fail to selectively activate different retinal pathways at sufficient spatial and temporal resolution. The development of improved stimulation strategies is rendered difficult by the large space of potential stimuli. Here we systematically explore a subspace of potential stimuli by electrically stimulating healthy and blind mouse retina in epiretinal configuration using smooth Gaussian white noise delivered by a high-density CMOS-based microelectrode array. We identify linear filters of retinal ganglion cells (RGCs) by fitting a linear-nonlinear-Poisson (LNP) model. Our stimulus evokes spatially and temporally confined spiking responses in RGC which are accurately predicted by the LNP model. Furthermore, we find diverse shapes of linear filters in the linear stage of the model, suggesting diverse preferred electrical stimuli of RGCs. The linear filter base identified by our approach could provide a starting point of a model-guided search for improved stimuli for retinal prosthetics.

Neural Spike Digital Detector on FPGA

This paper presents a multidisciplinary experiment where a population of neurons, dissociated from rat hippocampi, has been cultivated over a CMOS-based micro-electrode array (MEA) and its electrical activity has been detected and mapped by an advanced spike-sorting algorithm implemented on FPGA. MEAs are characterized by low signal-to-noise ratios caused by both the contactless sensing of weak extracellular voltages and the high noise power coming from cells and analog electronics signal processing. This low SNR forces to utilize advanced noise rejection algorithms to separate relevant neural activity from noise, which are usually implemented via software/off-line. However, off-line detection of neural spikes cannot be obviously used for real-time electrical stimulation. In this scenario, this paper presents a proper FPGA-based system capable to detect in real-time neural spikes from background noise. The output signals of the proposed system provide real-time spatial and temporal information about the culture electrical activity and the noise power distribution with a minimum latency of 165 ns. The output bit-stream can be further utilized to detect synchronous activity within the neural network.

Reflective lens-free imaging on high-density silicon microelectrode arrays for monitoring and evaluation of in vitro cardiac contractility.

The high rate of drug attrition caused by cardiotoxicity is a major challenge for drug development. Here, we developed a reflective lens-free imaging (RLFI) approach to non-invasively record in vitro cell deformation in cardiac monolayers with high temporal (169 fps) and non-reconstructed spatial resolution (352 µm) over a field-of-view of maximally 57 mm2. The method is compatible with opaque surfaces and silicon-based devices. Further, we demonstrated that the system can detect the impairment of both contractility and fast excitation waves in cardiac monolayers. Additionally, the RLFI device was implemented on a CMOS-based microelectrode array to retrieve multi-parametric information of cardiac cells, thereby offering more in-depth analysis of drug-induced (cardiomyopathic) effects for preclinical cardiotoxicity screening applications.

Simultaneous electrical and contractile monitoring of cardiomyocytes on silicon microelectrode arrays

Simultaneous electrical and contractile monitoring of cardiomyocytes on silicon microelectrode arrays

Single-Cell Electrical Stimulation with CMOS-based High-Density Microelectrode Arrays

Single-Cell Electrical Stimulation with CMOS-based High-Density Microelectrode Arrays

Temporal filters of electrically stimulated retinal ganglion cells

Event Abstract Back to Event Temporal filters of electrically stimulated retinal ganglion cells Larissa Hoefling1*, Philipp Berens2, 3, 4 and Günther Zeck1 1 Natural and Medical Sciences Institute, Germany 2 Institut für Ophthalmologische Forschung, Universität Tübingen, Germany 3 Werner Reichardt Centrum für Integrative Neurowissenschaften (CIN), Universität Tübingen, Germany 4 Bernstein Center for Computational Neuroscience, Germany Motivation Degenerative diseases like Retinitis Pigmentosa lead to blindness due to the degeneration of photoreceptors, while leaving the network of bipolar, horizontal, amacrine and ganglion cells largely intact. This remaining network can be stimulated electrically to evoke visual percepts, an approach that is already used in retinal implants. We stimulate rd10 mouse retinal ganglion cells (RGCs) using a smooth electrical stimulus waveform to mimic physiological retinal activity, and simultaneously record their responses to map temporal electrical filters (TEF). The TEFs could guide the development of more efficient stimulation protocols for retinal prostheses. Methods We use a high-density CMOS-based microelectrode array to simultaneously deliver smoothed white Gaussian noise stimuli via 1024 capacitive stimulation electrodes and record on 4225 recording electrodes from adult rd10 mouse retina prepared ex vivo and interfaced with the chip in flat-mount epiretinal configuration. Our approach allows recording of single neuron activity during stimulation without interference from stimulus artefacts. Custom-written data analysis software is used to recover the temporal electrical receptive fields of RGCs. Results Using a physiologically plausible smoothed white Gaussian noise stimulus, we are able to activate retinal ganglion cells at low current densities (≤1.5 mA/cm²). Ganglion cell activity is evoked and modulated in a reliable manner for repetitive stimulus presentations. We found two distinct types of TEFs for ON and OFF cells, respectively, suggesting that ON and OFF cells may be activated selectively. Conclusion We present and discuss smooth electrical stimulation as an alternative to pulsatile stimuli for electrically activating retinal ganglion cells in degenerating mouse retina. Acknowledgements Acknowldegement. This research is supported by a grant of the Baden Württemberg Stiftung (RetNetControl, FKZ: NEU 013) Keywords: Electrical Stimulation, receptive field properties, Temporal filters, retinal processing, linear nonlinear models, Retinal Ganglion Cells, CMOS-MEAs Conference: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018. Presentation Type: Poster Presentation Topic: Neural Networks Citation: Hoefling L, Berens P and Zeck G (2019). Temporal filters of electrically stimulated retinal ganglion cells. Conference Abstract: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays. doi: 10.3389/conf.fncel.2018.38.00082 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Mar 2018; Published Online: 17 Jan 2019. * Correspondence: Ms. Larissa Hoefling, Natural and Medical Sciences Institute, Reutlingen, Germany, larissa.hoefling@student.uni-tuebingen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Larissa Hoefling Philipp Berens Günther Zeck Google Larissa Hoefling Philipp Berens Günther Zeck Google Scholar Larissa Hoefling Philipp Berens Günther Zeck PubMed Larissa Hoefling Philipp Berens Günther Zeck Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

A Multi-Functional Microelectrode Array Featuring 59760 Electrodes, 2048 Electrophysiology Channels, Stimulation, Impedance Measurement and Neurotransmitter Detection Channels.

Biological cells are characterized by highly complex phenomena and processes that are, to a great extent, interdependent. To gain detailed insights, devices designed to study cellular phenomena need to enable tracking and manipulation of multiple cell parameters in parallel; they have to provide high signal quality and high spatiotemporal resolution. To this end, we have developed a CMOS-based microelectrode array system that integrates six measurement and stimulation functions, the largest number to date. Moreover, the system features the largest active electrode array area to date (4.48×2.43 mm2) to accommodate 59,760 electrodes, while its power consumption, noise characteristics, and spatial resolution (13.5 μm electrode pitch) are comparable to the best state-of-the-art devices. The system includes: 2,048 action-potential (AP, bandwidth: 300 Hz to 10 kHz) recording units, 32 local-field-potential (LFP, bandwidth: 1 Hz to 300 Hz) recording units, 32 current recording units, 32 impedance measurement units, and 28 neurotransmitter detection units, in addition to the 16 dual-mode voltage-only or current/voltage-controlled stimulation units. The electrode array architecture is based on a switch matrix, which allows for connecting any measurement/stimulation unit to any electrode in the array and for performing different measurement/stimulation functions in parallel.

Wavelength-sensitivity of mouse retinal ganglion cells recorded by a high-density micro electrode array (MEA)

Event Abstract Back to Event Wavelength-sensitivity of mouse retinal ganglion cells recorded by a high-density micro electrode array (MEA) Florian Jetter1, Gabriel Bertotti2, Roland Thewes3 and Günther Zeck4* 1 NMI at the University Tuebingen, Neurochip Research, Germany 2 Technische Universität Berlin, Chair of Sensor and Actuator Systems, Germany 3 Technische Universität Berlin, Chair of Sensor and Actuator Systems, Germany 4 NMI at the University Tuebingen, Neurochip Research, Germany Motivation: High-density CMOS-MEAs can be used to simultaneously record the electrical spiking activity from hundreds of neurons [Bertotti et al., 2014]. Neuronal spiking can be induced by electrical stimulation [Eickenscheidt and Zeck 2014], by light stimulation applied to a light-sensitive retina [Zeck et al. 2011], or by light stimulation of optogenetically transfected neurons [Herrmann et al. 2014]. In this work, we investigate the wavelength-sensitivity of different mouse retinal ganglion cells and the intrinsic wavelength-sensitivity of the response of high-density CMOS-MEAs. Material and Methods: A CMOS-based high-density MEA comprising 4225 recording sites is used for recording the ganglion cell activity in C57/Bl6 mouse retina during flickering light stimulation (1 and 5 Hz, respectively) with different wavelength and of different light stimulus sizes. Light stimuli presented on a DMD (µ-matrix, Rapp Optoelectronic, Germany) are focused through a microscope objective on the retina. The DMD is illuminated by an LED system commonly used for optogenetic activation (pe-4000, coolLED, UK). Here the results for four stimulation wavelengths are presented (405, 470, 525, and 635nm) at intensities as high as 2 mW/mm² (470 nm). Recorded data is sampled at 25 kHz. Results: Light stimulation (stimulus area: 1 mm2) evokes spiking in the interfaced retina. Based on the stimulus polarity retinal ganglion cells are broadly classified in ON or OFF type, depending on whether they respond to light on- or offset, respectively. In Fig. 1A filtered recordings are shown of the measured extracellular voltage from two selected sensors during 1 Hz stimulation. Both, ON and OFF cell types respond to the three highest wavelengths used here. The sensor site recording the ON transient cell also detects activity from a second OFF cell with smaller amplitude. In Fig.1B we present the unfiltered extracellular voltage traces recorded by a third selected sensor site for all four wavelengths. Light onset leads to a measurable change of the current in the sensing transistor (cf. Bertotti et al., 2014) or more generally speaking of the sensed recording site response, reflected as a low-frequency change of signal back-converted into the voltage domain. However, this does not prevent the detection of light-induced spiking. We note, that the ganglion cell shown in Fig. 1B is not activated by the 635 nm light stimulus. Ongoing experiments investigate the sensitivity of retinal ganglion cells to chromatic stimulation and to stimuli presented at various intensities. The induced variations of the sensor signals are wavelength-dependent, with the highest change obtained for the lowest wavelength (405 nm) and undetectable changes for red light (635 nm). Conclusion: It is shown that recording of cellular spiking activity with CMOS-based MEAs is possible during optical stimulation. Ganglion cells in the mouse retina have different wavelength-sensitivities. The light-induced low-frequency drift of the sensor signals can be completely removed for the tested wavelengths and intensities using high-pass filtering.

22.8 Multi-Functional Microelectrode Array System Featuring 59,760 Electrodes, 2048 Electrophysiology Channels, Impedance and Neurotransmitter Measurement Units.

Various CMOS-based micro-electrode arrays (MEAs) have been developed in recent years for extracellular electrophysiological recording/stimulation of electrogenic cells [1-5]. Mostly two approaches have been used: (i) the activepixel approach (APS) [2-4], which features simultaneous readout of all electrodes, however, at the expense of a comparably high noise level, and (ii) the switchmatrix (SM) approach, which yields better noise performance, whereas only a subset of electrodes (e.g.,1024) is simultaneously read out [5]. All systems feature, at most, voltage recording and/or voltage/current stimulation functionalities.

High-resolution CMOS MEA platform to study neurons at subcellular, cellular, and network levels.

Studies on information processing and learning properties of neuronal networks would benefit from simultaneous and parallel access to the activity of a large fraction of all neurons in such networks. Here, we present a CMOS-based device, capable of simultaneously recording the electrical activity of over a thousand cells in in vitro neuronal networks. The device provides sufficiently high spatiotemporal resolution to enable, at the same time, access to neuronal preparations on subcellular, cellular, and network level. The key feature is a rapidly reconfigurable array of 26 400 microelectrodes arranged at low pitch (17.5 μm) within a large overall sensing area (3.85 × 2.10 mm(2)). An arbitrary subset of the electrodes can be simultaneously connected to 1024 low-noise readout channels as well as 32 stimulation units. Each electrode or electrode subset can be used to electrically stimulate or record the signals of virtually any neuron on the array. We demonstrate the applicability and potential of this device for various different experimental paradigms: large-scale recordings from whole networks of neurons as well as investigations of axonal properties of individual neurons.

Development of a Reliable Packaging for CMOS-based Microelectrode Arrays by Using an Automated Setup

We present a reliable and versatile microelectrode-array-device-packaging method for use in neurobiological research. The new packaging is simple, user-friendly, durable, and obviates any contamination of the sensitive electrodes (Figure 1). The packaging consists of a custom-designed injection-molded polycarbonate ring that is bonded to the surface of the CMOS chip with a specifically selected biocompatible adhesive. The utilization of capillary effects (Figure 3) in the packaging design eliminates any contamination and flooding of the sensitive electrode array by the adhesive compound or other substances.During the development phase, an automated setup was designed to measure the lifespan of the packaging; this setup was used to determine the optimal dimensions, appropriate adhesive compound and other required parameters.

Prolog to "Growing Cells Atop Microelectronic Chips: Interfacing Electrogenic Cells In Vitro With CMOS-Based Microelectrode Arrays"

To grasp the challenges and potentials faced, an overview of the fundamentals of recording electrical cell activity is in order. Many types of cells can undergo a transient electrical depolarization and repolarization, triggered by external mechanisms or by intracellular, spontaneous mechanisms. Cells that can generate electrical signals are called electrogenic cells. The most common types of electrogenic cells are brain cells (neurons) and heart cells (cardiomyocytes). The biology of electrogenic cells is complex, a symphonic interdependence of electrical, electrophysiological and biochemical processes. This requires an understanding of mechanisms underlying the functioning of voltage-gated ion channels, the generation of action potentials, and the conduction of action potentials through a cellular network.

Growing Cells Atop Microelectronic Chips: Interfacing Electrogenic Cells In Vitro With CMOS-Based Microelectrode Arrays

Complementary semiconductor-metal-oxide (CMOS) technology is a very powerful technology that can be more or less directly interfaced to electrogenic cells, like heart or brain cells in vitro. To this end, the cells are cultured directly atop the CMOS chips, which usually undergo dedicated postprocessing to obtain a reliable bidirectional interface via noble-metal microelectrodes or high-k dielectrics. The big advantages of using CMOS integrated circuits (ICs) include connectivity, the possibility to address a large number of microelectrodes on a tiny chip, and signal quality, the possibility to condition small signals right at the spot of their generation. CMOS will be demonstrated to constitute an enabling technology that opens a route to high-spatio-temporal-resolution and low-noise electrophysiological recordings from a variety of biological preparations, such as brain slices, or cultured cardiac and brain cells. The recording technique is extracellular and noninvasive, and the CMOS chips do not leak out any toxic compounds, so that the cells remain viable for extended times. In turn, the CMOS chips have been demonstrated to survive several months of culturing while being fully immersed in saline solution and being exposed to cellular metabolic products. The latter requires dedicated passivation and packaging techniques as will be shown. Fully integrated, monolithic microelectrode systems, which feature large numbers of tightly spaced microelectrodes and the associated circuitry units for bidirectional interaction (stimulation and recording), will be in the focus of this review. The respective dense microelectrode arrays (MEAs) with small pixels enable subcellular-resolution investigation of regions of interest in, e.g., neurobiological preparations, and, at the same time, the large number of electrodes allows for studying the activity of entire neuronal networks . Application areas include neuroscience, as the devices enable fundamental neurophysiological insights at the cellular and circuit level, as well as medical diagnostics and pharmacology.

Tracking burst patterns in hippocampal cultures with high-density CMOS-MEAs

In this work, we investigate the spontaneous bursting behaviour expressed by in vitro hippocampal networks by using a high-resolution CMOS-based microelectrode array (MEA), featuring 4096 electrodes, inter-electrode spacing of 21 µm and temporal resolution of 130 µs. In particular, we report an original development of an adapted analysis method enabling us to investigate spatial and temporal patterns of activity and the interplay between successive network bursts (NBs). We first defined and detected NBs, and then, we analysed the spatial and temporal behaviour of these events with an algorithm based on the centre of activity trajectory. We further refined the analysis by using a technique derived from statistical mechanics, capable of distinguishing the two main phases of NBs, i.e. (i) a propagating and (ii) a reverberating phase, and by classifying the trajectory patterns. Finally, this methodology was applied to signal representations based on spike detection, i.e. the instantaneous firing rate, and directly based on voltage-coded raw data, i.e. activity movies. Results highlight the potentialities of this approach to investigate fundamental issues on spontaneous neuronal dynamics and suggest the hypothesis that neurons operate in a sort of ‘team’ to the perpetuation of the transmission of the same information.

Switch-Matrix-Based High-Density Microelectrode Array in CMOS Technology

We report on a CMOS-based microelectrode array (MEA) featuring 11, 011 metal electrodes and 126 channels, each of which comprises recording and stimulation electronics, for extracellular bidirectional communication with electrogenic cells, such as neurons or cardiomyocytes. The important features include: (i) high spatial resolution at (sub)cellular level with 3150 electrodes per mm2 (electrode diameter 7 ?m, electrode pitch 18 ?m); (ii) a reconflgurable routing of the recording sites to the 126 channels; and (iii) low noise levels.