Microelectrode Array Technology Research Articles

A 200-Channel Area-Power-Efficient Chemical and Electrical Dual-Mode Acquisition IC for the Study of Neurodegenerative Diseases.

Microelectrode array (MEA) can be used in the study of neurodegenerative diseases by monitoring the chemical neurotransmitter release and the electrical potential simultaneously at the cellular level. Currently, the MEA technology is migrating to more electrodes and higher electrode density, which raises power and area constraints on the design of acquisition IC. In this paper, we report the design of a 200-channel dual-mode acquisition IC with highly efficient usage of power and area. Under the constraints of target noise and fast settling, the current channel design saves power by including a novel current buffer biased in discrete time (DT) before the TIA (transimpedance amplifier). The 200 channels are sampled at 20 kS/s and quantized by column-wise SAR ADCs. The prototype IC was fabricated in a 0.18 μm CMOS process. Silicon measurements show the current channel has 21.6 pArms noise with cyclic voltammetry (CV) and 0.48 pArms noise with constant amperometry (CA) while consuming 12.1 μW . The voltage channel has 4.07 μVrms noise in the bandwidth of 100 kHz and 0.2% nonlinearity while consuming 9.1 μW. Each channel occupies 0.03 mm(2) area, which is among the smallest.

A method for electrophysiological characterization of hamster retinal ganglion cells using a high-density CMOS microelectrode array.

Knowledge of neuronal cell types in the mammalian retina is important for the understanding of human retinal disease and the advancement of sight-restoring technology, such as retinal prosthetic devices. A somewhat less utilized animal model for retinal research is the hamster, which has a visual system that is characterized by an area centralis and a wide visual field with a broad binocular component. The hamster retina is optimally suited for recording on the microelectrode array (MEA), because it intrinsically lies flat on the MEA surface and yields robust, large-amplitude signals. However, information in the literature about hamster retinal ganglion cell functional types is scarce. The goal of our work is to develop a method featuring a high-density (HD) complementary metal-oxide-semiconductor (CMOS) MEA technology along with a sequence of standardized visual stimuli in order to categorize ganglion cells in isolated Syrian Hamster (Mesocricetus auratus) retina. Since the HD-MEA is capable of recording at a higher spatial resolution than most MEA systems (17.5 μm electrode pitch), we were able to record from a large proportion of RGCs within a selected region. Secondly, we chose our stimuli so that they could be run during the experiment without intervention or computation steps. The visual stimulus set was designed to activate the receptive fields of most ganglion cells in parallel and to incorporate various visual features to which different cell types respond uniquely. Based on the ganglion cell responses, basic cell properties were determined: direction selectivity, speed tuning, width tuning, transience, and latency. These properties were clustered to identify ganglion cell types in the hamster retina. Ultimately, we recorded up to a cell density of 2780 cells/mm2 at 2 mm (42°) from the optic nerve head. Using five parameters extracted from the responses to visual stimuli, we obtained seven ganglion cell types.

In vitro studies of neuronal networks and synaptic plasticity in invertebrates and in mammals using multielectrode arrays.

Brain functions are strictly dependent on neural connections formed during development and modified during life. The cellular and molecular mechanisms underlying synaptogenesis and plastic changes involved in learning and memory have been analyzed in detail in simple animals such as invertebrates and in circuits of mammalian brains mainly by intracellular recordings of neuronal activity. In the last decades, the evolution of techniques such as microelectrode arrays (MEAs) that allow simultaneous, long-lasting, noninvasive, extracellular recordings from a large number of neurons has proven very useful to study long-term processes in neuronal networks in vivo and in vitro. In this work, we start off by briefly reviewing the microelectrode array technology and the optimization of the coupling between neurons and microtransducers to detect subthreshold synaptic signals. Then, we report MEA studies of circuit formation and activity in invertebrate models such as Lymnaea, Aplysia, and Helix. In the following sections, we analyze plasticity and connectivity in cultures of mammalian dissociated neurons, focusing on spontaneous activity and electrical stimulation. We conclude by discussing plasticity in closed-loop experiments.

A Low-Noise, Modular, and Versatile Analog Front-End Intended for ProcessingIn VitroNeuronal Signals Detected by Microelectrode Arrays

The collection of good quality extracellular neuronal spikes from neuronal cultures coupled to Microelectrode Arrays (MEAs) is a binding requirement to gather reliable data. Due to physical constraints, low power requirement, or the need of customizability, commercial recording platforms are not fully adequate for the development of experimental setups integrating MEA technology with other equipment needed to perform experiments under climate controlled conditions, like environmental chambers or cell culture incubators. To address this issue, we developed a custom MEA interfacing system featuring low noise, low power, and the capability to be readily integrated inside an incubator-like environment. Two stages, a preamplifier and a filter amplifier, were designed, implemented on printed circuit boards, and tested. The system is characterized by a low input-referred noise (<1 μV RMS), a high channel separation (>70 dB), and signal-to-noise ratio values of neuronal recordings comparable to those obtained with the benchmark commercial MEA system. In addition, the system was successfully integrated with an environmental MEA chamber, without harming cell cultures during experiments and without being damaged by the high humidity level. The devised system is of practical value in the development of in vitro platforms to study temporally extended neuronal network dynamics by means of MEAs.

GW25-e1095 Cardiac Electrical Activity Improved by Overexpression of the Sarcoplasmic Reticulum Ca2+-ATPase in Rat Myocardial Failure After Myocardial Infarction Evaluated by Microelectrode Arrays Technology

GW25-e1095 Cardiac Electrical Activity Improved by Overexpression of the Sarcoplasmic Reticulum Ca2+-ATPase in Rat Myocardial Failure After Myocardial Infarction Evaluated by Microelectrode Arrays Technology

Tonic glutamate in CA1 of aging rats correlates with phasic glutamate dysregulation during seizure.

Characterize glutamate neurotransmission in the hippocampus of awake-behaving rodents during focal seizures in a model of aging. We used enzyme-based ceramic microelectrode array technology to measure in vivo extracellular tonic glutamate levels and real-time phasic glutamate release and clearance events in the hippocampus of awake Fischer 344 rats. Local application of 4-aminopyridine (4-AP) into the CA1 region was used to induce focal motor seizures in different animal age groups representing young, late-middle aged and elderly humans. Rats with the highest preseizure tonic glutamate levels (all in late-middle aged or elderly groups) experienced the most persistent 4-AP-induced focal seizure motor activity (wet dog shakes) and greatest degree of acute seizure-associated disruption of glutamate neurotransmission measured as rapid transient changes in extracellular glutamate levels. Increased seizure susceptibility was demonstrated in the rats with the highest baseline hippocampal extracellular glutamate levels, all of which were late-middle aged or aged animals. The manifestation of seizures behaviorally was associated with dynamic changes in glutamate neurotransmission. To our knowledge, this is the first report of a relationship between seizure susceptibility and alterations in both baseline tonic and phasic glutamate neurotransmission.

Chronic, percutaneous connector for electrical recording and stimulation with microelectrode arrays.

The translation of advances in neural stimulation and recording research into clinical practice hinges on the ability to perform chronic experiments in awake and behaving animal models. Advances in microelectrode array technology, most notably flexible polymer arrays, have significantly improved reliability of the neural interface. However, electrical connector technology has lagged and is prone to failure from non-biocompatibility, large size, contamination, corrosion, and difficulty of use. We present a novel chronic, percutaneous electrical connector system that is suitable for neural stimulation and recording. This system features biocompatible materials, low connect and disconnect forces, passive alignment, and a protective cap during non-use. We have successfully designed, assembled, and tested in vitro both a 16-channel system and a high density 64-channel system. Custom, polyimide, 16-channel, microelectrode arrays were electrically assembled with the connector system and tested using cyclic voltammetry and electrochemical impedance spectroscopy. This connector system is versatile and can be used with a variety of microelectrode array technologies for chronic studies.

Recent trends in microelectrode array technology for in vitro neural interface platform

Microelectrode array (MEA) technology is a widely used platform for the study of in vitro neural networks as it can either record or stimulate neurons by accessing multiple sites of neural circuits simultaneously. Unlike intracellular recording techniques, MEAs form noninvasive interface with cells so that they provides relatively long time window for studying neural circuits. As the technology matured, there have been various engineering solutions to meet the requirements in diverse application areas of MEAs: High-density MEAs, high-throughput platforms, flexible electrodes, monitoring subthreshold activity, co-culture platforms, and surface micropatterning. The MEA technology has been applied to neural network analysis, drug screening and neural prostheses studies. In this paper, the MEA technology is reviewed and the future prospect is discussed.

A PDMS-Based Integrated Stretchable Microelectrode Array (isMEA) for Neural and Muscular Surface Interfacing

Numerous applications in neuroscience research and neural prosthetics, such as electrocorticogram (ECoG) recording and retinal prosthesis, involve electrical interactions with soft excitable tissues using a surface recording and/or stimulation approach. These applications require an interface that is capable of setting up high-throughput communications between the electrical circuit and the excitable tissue and that can dynamically conform to the shape of the soft tissue. Being a compliant material with mechanical impedance close to that of soft tissues, polydimethylsiloxane (PDMS) offers excellent potential as a substrate material for such neural interfaces. This paper describes an integrated technology for fabrication of PDMS-based stretchable microelectrode arrays (MEAs). Specifically, as an integral part of the fabrication process, a stretchable MEA is directly fabricated with a rigid substrate, such as a thin printed circuit board (PCB), through an innovative bonding technology-via-bonding-for integrated packaging. This integrated strategy overcomes the conventional challenge of high-density packaging for this type of stretchable electronics. Combined with a high-density interconnect technology developed previously, this stretchable MEA technology facilitates a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. In this paper, this PDMS-based integrated stretchable MEA (isMEA) technology is demonstrated by an example design that packages a stretchable MEA with a small PCB. The resulting isMEA is assessed for its biocompatibility, surface conformability, electrode impedance spectrum, and capability to record muscle fiber activity when applied epimysially.

High Precision Release of Neurotransmitter - A New Tool

Modern imaging techniques have become a powerful tool for investigating excitation patterns and signaling pathways in the brain. However, the high complexity of brain topology and the resolution limit of in vivo techniques make it difficult to study isolated small neuron circuits. Micro-electrode arrays (MEAs) are able to record activity of in vitro neuron networks and to stimulate locally, but such electrical approach cannot easily be applied to stimulate single cells. Large stimulus artifacts and poor control over the spread of electrical stimuli in medium create the main disadvantages when studying the role of single cells in small networks. One promising solution is to interact with individual neural cells by mimicking chemical signaling. Recently developed systems for precise neurotransmitter release include micropipettes, microfluidic substrates and caged compounds. In this project we propose to combine MEA technology (Multi Channel Systems GmbH, Switzerland) with novel FluidFM technology. The FluidFM (Cytosurge AG, Switzerland) has hollow atomic-force microscopy (AFM) cantilevers acting as force-controlled nanopipettes. We present the ability to locally release neurotransmitters on the cell membrane with precise control over applied force (sub-nN) and spatial position (μm). For those experiments we used FluidFM cantilevers with 2 μm openings, where the microfluidic channel was filled with physiological solution containing 200 μM glutamate. In order to chemically induce a local electrical response in a culture of dissociated hippocampal neurons from E18 rat, we first brought the FluidFM cantilever in contact with the cell membrane. We then applied pressure-pulses between 50 mbar and 300 mbar with 300 ms duration to locally eject sub picoliter volumes of the neurotransmitter. We are now working towards applying single cell stimulations to well defined networks.

Sparse Optimal Motor Estimation (SOME) for Extracting Commands for Prosthetic Limbs

It is possible to replace amputated limbs with mechatronic prostheses, but their operation requires the user's intentions to be detected and converted into control signals to the actuators. Fortunately, the motoneurons (MNs) that controlled the amputated muscles remain intact and capable of generating electrical signals, but these signals are difficult to record. Even the latest microelectrode array technologies and targeted motor reinnervation can provide only sparse sampling of the hundreds of motor units that comprise the motor pool for each muscle. Simple rectification and integration of such records is likely to produce noisy and delayed estimates of the actual intentions of the user. We have developed a novel algorithm for optimal estimation of motor pool excitation based on the recruitment and firing rates of a small number (2-10) of discriminated motor units. We first derived the motor estimation algorithm from normal patterns of modulated MN activity based on a previously published model of individual MN recruitment and asynchronous frequency modulation. The algorithm was then validated on a target motor reinnervation subject using intramuscular fine-wire recordings to obtain single motor units.

A Topographically Modified Substrate-Embedded MEA for Directed Myotube Formation at Electrode Contact Sites

Myoblast fusion into functionally distinct myotubes, and their subsequent integration with the nervous system, is a poorly understood phenomenon with important applications in basic science research, skeletal muscle tissue engineering, and cell-based biosensor development. We have previously demonstrated the ability of microelectrode arrays (MEAs) to record the extracellular action potentials of myotubes, and we have shown that this information reveals the presence of multiple, electrophysiologically independent myotubes even in unstructured cultures where there is extensive physical contact between cells (Langhammer et al., Biotechnol Prog 27:891-895, 2011). In this paper, we explore the ability of microscale topographical trenches to guide the myoblast alignment and fusion processes and use our findings to create a substrate-embedded MEA containing topographical trenches that are able to direct myotube contractility to specific locations. By combining substrate-embedded MEA technology with topographical patterns, we have developed a lab-on-a-chip test bed for the non-invasive examination of myotubes.

Vertically Aligned Carbon Nanotubes for Microelectrode Arrays Applications

In this work a methodology to fabricate carbon nanotube based electrodes using plasma enhanced chemical vapour deposition has been explored and defined. The final integrated microelectrode based devices should present specific properties that make them suitable for microelectrode arrays applications. The methodology studied has been focused on the preparation of highly regular and dense vertically aligned carbon nanotube (VACNT) mat compatible with the standard lithography used for microelectrode arrays technology.

Abstract 115: The Changes in Cardioelectrical Activity of Rat With Myocardial Infarction Receiving Sarcoplasmic Reticulum Ca 2+ -ATPase Gene Modified Bone Marrow Stem Cell Transplantation by Microelectrode Array Technology

0bjective Comparison of bone marrow stem cells (BMSCs) transplantation and sarcoplasmic reticulum Ca 2+ -ATPase (SERCA2a) gene modified BMSCs transplantation for therapy effects after acute myocardial infarction(AMI), as well as for assessment cardiac electrical activity by microelectrode array (MEA) technology. Methods Rats with myocardial infarction ( n =24)and divided into 3 groups randomly: Sham group ( n =8), BMSCs group( n =8) and SERCA2a gene modified BMSCs transplantation group (BMSCs+rAd.SERCA2a group, n =8). After 14 days, cardiac function was evaluated by echocardiography and heart electrical activity was evaluated by electrocardiogram and MEA technology. Results (1)The transduction ration of rAd.SERCa2a to BMSCs were 80% to 90%. (2)Compared to sham group, BMSCs group and BMSCs+rAd.SERCA2a group could significantly improve cardiac function on 14 days after therapy ( n =6, P &lt;0.05).(3)QT duration of BMSCs+rAd.SERCA2a group was significantly shorter than in the sham group(80.30 ms±6.53 ms versus 105.31 ms±21.89 ms),the mean value was significantly decreased 23.8%( n =7, P &lt;0.05). Ventricular premature beats were also recorded in rats from sham group.(4)MEA results suggested that isolated heart beats were significantly slowed and ventricular arrhythmias and atrioventrocular block were recorded in sham group. The maximum field potential and field potential duration of infarcted myocardium area in BMSCs group and BMSCs+rAd.SERCA2a group were significantly longer than those in sham group(the maximum field potential: 0.51 mV±0.15 mV, 0.55 mV±0.16 mV, 0.23 mV±0.1mV; field potential duration: 104.5 ms±25.43 ms, 107.67 ms ±24.01 ms, 63 ms± 20.34 ms; n =6, P &lt;0.05).(5)The conduction time was the shortest in BMSCs+rAd.SERCA2a group, the cardiac electrical conduction could keep consistency and improve in myocardial infarction tissue. Conclusions In short time, BMSCs and SERCA2a gene modified BMSCs transplantation could obviously enhance cardiac function. BMSCs+rAd.SERCA2a group could effectively improve electrical conduction of infarcted myocardium and block the occurrence of arrhythmia after myocardial infarction.

Leptin Counteracts the Hypoxia-Induced Inhibition of Spontaneously Firing Hippocampal Neurons: A Microelectrode Array Study

Besides regulating energy balance and reducing body-weight, the adipokine leptin has been recently shown to be neuroprotective and antiapoptotic by promoting neuronal survival after excitotoxic and oxidative insults. Here, we investigated the firing properties of mouse hippocampal neurons and the effects of leptin pretreatment on hypoxic damage (2 hours, 3% O2). Experiments were carried out by means of the microelectrode array (MEA) technology, monitoring hippocampal neurons activity from 11 to 18 days in vitro (DIV). Under normoxic conditions, hippocampal neurons were spontaneously firing, either with prevailing isolated and randomly distributed spikes (11 DIV), or with patterns characterized by synchronized bursts (18 DIV). Exposure to hypoxia severely impaired the spontaneous activity of hippocampal neurons, reducing their firing frequency by 54% and 69%, at 11 and 18 DIV respectively, and synchronized their firing activity. Pretreatment with 50 nM leptin reduced the firing frequency of normoxic neurons and contrasted the hypoxia-induced depressive action, either by limiting the firing frequency reduction (at both ages) or by increasing it to 126% (in younger neurons). In order to find out whether leptin exerts its effect by activating large conductance Ca2+-activated K+ channels (BK), as shown on rat hippocampal neurons, we applied the BK channel blocker paxilline (1 µM). Our data show that paxilline reversed the effects of leptin, both on normoxic and hypoxic neurons, suggesting that the adipokine counteracts hypoxia through BK channels activation in mouse hippocampal neurons.

Ammonium chloride influences in vitro-neuronal network activity

The objective of the present work is to image functional alterations in hepatic encephalopathy (HE) by ammonia-induced changes of in vitro-neuronal network activity and to identify counteracting strategies.Synchronous bursting behavior of rat cortical cells which is the result of synaptic interaction of excitatory and inhibitory neurons was recorded in vitro on microelectrode arrays (MEAs) after ammonium chloride exposure. In order to test the involvement of astrocytic glutamine metabolism and N-methyl-d-aspartic acid- (NMDA-) receptor function in the observed ammonia-induced network dysregulation and to identify potentially protective strategies, we investigated effects of the glutamine synthetase (GS) inhibitor methionine–sulfoximine (MSO) and the NMDA-receptor antagonist DL-2-Amino-5-phosphono-pentanoic acid (AP-5), respectively.We observed a characteristic ammonia-induced increase of global network activity while network synchrony was suppressed. The increase of global activity, but not the suppression of network synchrony was prevented by inhibiting GS. However, blocking NMDA-receptors prevented both, network excitation and desynchronization.Conclusions: 1. The observed desynchronization of in vitro-neuronal network activity after ammonium chloride treatment might reflect global neuronal network changes in HE in vivo and suggests the MEA technology as a valuable tool for measuring changes of neuronal connectivity in vitro. 2. Astrocytic glutamine metabolism might be involved in increased global network activity, but not in the suppression of network synchrony. 3. Overactivation of NMDA-receptors might underlie both, the ammonia-induced increase of activity and suppression of network synchrony, suggesting that NMDA-receptor function is involved in HE and that their blockage might be protective. 4. Measuring neuronal network activity in vitro by the MEA technology might help to describe functionally protective measures in HE.

Adult neural progenitor cells reactivate superbursting in mature neural networks

Behavioral recovery in animal models of human CNS syndromes suggests that transplanted stem cell derivatives can augment damaged neural networks but the mechanisms behind potentiated recovery remain elusive. Here we use microelectrode array (MEA) technology to document neural activity and network integration as rat primary neurons and rat hippocampal neural progenitor cells (NPCs) differentiate and mature. The natural transition from neuroblast to functional excitatory neuron consists of intermediate phases of differentiation characterized by coupled activity. High-frequency network-wide bursting or “superbursting” is a hallmark of early plasticity that is ultimately refined into mature stable neural network activity. Microelectrode array (MEA)-plated neurons transition through this stage of coupled superbursting before establishing mature neuronal phenotypes in vitro. When plated alone, adult rat hippocampal NPC-derived neurons fail to establish the synchronized bursting activity that neurons in primary and embryonic stem cell-derived cultures readily form. However, adult rat hippocampal NPCs evoke re-emergent superbursting in electrophysiologically mature rat primary neural cultures. Developmental superbursting is thought to accompany transient states of heightened plasticity both in culture preparations and across brain regions. Future work exploring whether NPCs can re-stimulate developmental states in injury models would be an interesting test of their regenerative potential.

Tonic and phasic release of glutamate and acetylcholine neurotransmission in sub-regions of the rat prefrontal cortex using enzyme-based microelectrode arrays

The medial prefrontal cortex (mPFC) is an area of the brain critical for higher cognitive processes and implicated in disorders of the CNS such as drug addiction, depression and schizophrenia. Glutamate and acetylcholine are neurotransmitters that are essential for cortical functioning, yet little is known about the dynamic function of these neurotransmitters in subregions of the mPFC. In these studies we used a novel microelectrode array technology to measure resting levels (tonic release) of glutamate and acetylcholine as well as KCl-evoked release (stimulated phasic release) in the mPFC of the anesthetized rat to further our understanding of both tonic and phasic neurotransmission in the cingulate cortex, prelimbic cortex, and infralimbic cortex of the mPFC. Studies revealed homogeneity of tonic and phasic signaling among brain subregions for each neurotransmitter. However, resting levels of glutamate were significantly higher as compared to acetylcholine levels in all subregions. Additionally, KCl-evoked acetylcholine release in the cingulate cortex (7.1 μM) was significantly greater than KCl-evoked glutamate release in any of the three subregions (Cg1, 2.9 μM; PrL, 2.0 μM; IL, 1.8 μM). Interestingly, the time for signal decay following KCl-evoked acetylcholine release was significantly longer by an average of 240% as compared to KCL-evoked glutamate release for all three brain subregions. Finally, we observed a negative relationship between acetylcholine resting levels and KCl-evoked release in the Cg1. These data suggest a homogenous distribution of both glutamatergic and acetylcholinergic innervation in the mPFC, with alterations in tonic and phasic release regulation accounting for differences between these neurotransmitters.

Methodology for rapid measures of glutamate release in rat brain slices using ceramic-based microelectrode arrays: Basic characterization and drug pharmacology

Excessive excitability or hyperexcitability of glutamate-containing neurons in the brain has been proposed as a possible explanation for anxiety, stress-induced disorders, epilepsy, and some neurodegenerative diseases. However, direct measurement of glutamate on a rapid time scale has proven to be difficult. Here we adapted enzyme-based microelectrode arrays (MEA) capable of detecting glutamate in vivo, to assess the effectiveness of hyperexcitability modulators on glutamate release in brain slices of the rat neocortex. Using glutamate oxidase coated ceramic MEAs coupled with constant voltage amperometry, we measured resting glutamate levels and synaptic overflow of glutamate after K + stimulation in brain slices. MEAs reproducibly detected glutamate on a second-by-second time scale in the brain slice preparation after depolarization with high K + to evoke glutamate release. This stimulus-evoked glutamate release was robust, reproducible, and calcium dependent. The K +-evoked glutamate release was modulated by ligands to the α 2δ subunit of voltage sensitive calcium channels (PD-0332334 and PD-0200390). Meanwhile, agonists to Group II metabotropic glutamate (mGlu) receptors (LY379268 and LY354740), which are known to alter hyperexcitability of glutamate neurons, attenuated K +-evoked glutamate release but did not alter resting glutamate levels. This new MEA technology provides a means of directly measuring the chemical messengers involved in glutamate neurotransmission and thereby helping to reveal the role multiple glutamatergic system components have on glutamate signaling.

Skeletal myotube integration with planar microelectrode arrays in vitro for spatially selective recording and stimulation: A comparison of neuronal and myotube extracellular action potentials

Microelectrode array (MEA) technology holds tremendous potential in the fields of biodetection, lab-on-a-chip applications, and tissue engineering by facilitating noninvasive electrical interaction with cells in vitro. To date, significant efforts at integrating the cellular component with this detection technology have worked exclusively with neurons or cardiac myocytes. We investigate the feasibility of using MEAs to record from skeletal myotubes derived from primary myoblasts as a way of introducing a third electrogenic cell type and expanding the potential end applications for MEA-based biosensors. We find that the extracellular action potentials (EAPs) produced by spontaneously contractile myotubes have similar amplitudes to neuronal EAPs. It is possible to classify myotube EAPs by biological signal source using a shape-based spike sorting process similar to that used to analyze neural spike trains. Successful spike-sorting is indicated by a low within-unit variability of myotube EAPs. Additionally, myotube activity can cause simultaneous activation of multiple electrodes, in a similar fashion to the activation of electrodes by networks of neurons. The existence of multiple electrode activation patterns indicates the presence of several large, independent myotubes. The ability to identify these patterns suggests that MEAs may provide an electrophysiological basis for examining the process by which myotube independence is maintained despite rapid myoblast fusion during differentiation. Finally, it is possible to use the underlying electrodes to selectively stimulate individual myotubes without stimulating others nearby. Potential uses of skeletal myotubes grown on MEA substrates include lab-on-a-chip applications, tissue engineering, co-cultures with motor neurons, and neural interfaces.