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In JoVE (4)
- वर्चुअल कर्सर आंदोलन के लिए BCI2000 के साथ एक ईईजी के आधार मस्तिष्क - कंप्यूटर इंटरफेस का उपयोग
- कैंसर स्टेम सेल प्रवासन compartmentalizing microfluidic उपकरणों और जीना सेल इमेजिंग का उपयोग का मूल्यांकन
- एकल यूनिट गतिविधि और Electrocorticographic सिग्नल रिकॉर्डिंग के लिए जीर्ण तंत्रिका इलेक्ट्रोड की शल्य आरोपण
- वोल्टेज biasing, चक्रीय Voltammetry, और तंत्रिका इंटरफेस के लिए विद्युत प्रतिबाधा स्पेक्ट्रोस्कोपी
Other Publications (31)
- IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
- IEEE Transactions on Bio-medical Engineering
- Lab on a Chip
- JAMA : the Journal of the American Medical Association
- IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
- Journal of Neural Engineering
- Journal of Neural Engineering
- IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society
- Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
- Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
- Journal of Neural Engineering
- Lab on a Chip
- Journal of Neurosurgery
- Biomaterials
- Epilepsy & Behavior : E&B
- Frontiers in Neuroengineering
- Neuron
- Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
- Conference Proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
- Lab on a Chip
- Journal of Neuroscience Methods
- Lab on a Chip
- Stem Cells (Dayton, Ohio)
- Langmuir : the ACS Journal of Surfaces and Colloids
- ACS Nano
- Biomicrofluidics
- Clinical EEG and Neuroscience : Official Journal of the EEG and Clinical Neuroscience Society (ENCS)
- Microscopy and Microanalysis : the Official Journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada
- Lab on a Chip
- Ergonomics
- Lab on a Chip
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Articles by Justin C. Williams in JoVE
JoVE General
वर्चुअल कर्सर आंदोलन के लिए BCI2000 के साथ एक ईईजी के आधार मस्तिष्क - कंप्यूटर इंटरफेस का उपयोग
1Department of Biomedical Engineering, University of Wisconsin-Madison, 2Wadsworth Center, New York State Dept. of Health
इस वीडियो में, हम एक मस्तिष्क कंप्यूटर इंटरफेस प्रयोग, ईईजी टोपी की स्थापना, सिस्टम औजार, और कल्पना आंदोलनों का उपयोग कर दो आयामों में एक कर्सर को स्थानांतरित करने के लिए उपयोगकर्ता प्रशिक्षण सहित चलाने के लिए आवश्यक कदम प्रदर्शित करता है.
JoVE Clinical and Translational Medicine
कैंसर स्टेम सेल प्रवासन compartmentalizing microfluidic उपकरणों और जीना सेल इमेजिंग का उपयोग का मूल्यांकन
1Department of Biomedical Engineering, University of Wisconsin-Madison, 2Materials Science Program, University of Wisconsin-Madison, 3Department of Neurological Surgery, University of Wisconsin-Madison, 4Carbone Comprehensive Cancer Center and Center for Stem Cell and Regenerative Medicine, University of Wisconsin-Madison
कैंसर स्टेम सेल प्रवास की जांच करने के लिए एक compartmentalizing microfluidic युक्ति वर्णित है. इस उपन्यास मंच एक व्यवहार्य सेलुलर microenvironment बनाता है और जीवित कोशिका हरकत के सूक्ष्म दृश्य में सक्षम बनाता है. अत्यधिक गतिशील कैंसर की कोशिकाओं को आक्रामक घुसपैठ के आणविक तंत्र, संभवतः अधिक प्रभावी भविष्य उपचार के लिए अग्रणी का अध्ययन करने के लिए अलग कर रहे हैं.
JoVE Neuroscience
एकल यूनिट गतिविधि और Electrocorticographic सिग्नल रिकॉर्डिंग के लिए जीर्ण तंत्रिका इलेक्ट्रोड की शल्य आरोपण
1Biomedical Engineering, University of Michigan, 2Biomedical Engineering, University of Wisconsin-Madison, 3NeuroNexus Technologies
हम सर्जनों जो पुरानी तंत्रिका रिकॉर्डिंग इलेक्ट्रोड दाखिल करने की प्रक्रिया सीख रहे हैं के लिए उपयोगी जानकारी प्रदान करते हैं. दोनों मर्मज्ञ और सतह इलेक्ट्रोड प्रणालियों के लिए तकनीक एक कृंतक पशु मॉडल में वर्णित हैं.
JoVE Neuroscience
वोल्टेज biasing, चक्रीय Voltammetry, और तंत्रिका इंटरफेस के लिए विद्युत प्रतिबाधा स्पेक्ट्रोस्कोपी
1Weldon School of Biomedical Engineering, Purdue University, 2Biomedical Engineering, University of Wisconsin-Madison, 3Biomedical Engineering, University of Michigan, 4Department of Biological Sciences, Purdue University
इलेक्ट्रोड ऊतक तंत्रिका रिकॉर्डिंग इलेक्ट्रोड के इंटरफ़ेस विद्युत प्रतिबाधा (EIS) स्पेक्ट्रोस्कोपी और चक्रीय voltammetry (सीवी) के साथ लक्षण वर्णन किया जा सकता है. वोल्टेज परिवर्तन biasing पर ऊतक इंटरफ़ेस इलेक्ट्रोड की विद्युत गुणों में सुधार कर सकते हैं रिकॉर्डिंग क्षमता के आवेदन. वोल्टेज biasing, EIS, CV, और तंत्रिका रिकॉर्डिंग पूरक हैं.
Other articles by Justin C. Williams on PubMed
Silicon-substrate Intracortical Microelectrode Arrays for Long-term Recording of Neuronal Spike Activity in Cerebral Cortex
This study investigated the use of planar, silicon-substrate microelectrodes for chronic unit recording in the cerebral cortex. The 16-channel microelectrodes consisted of four penetrating shanks with four recording sites on each shank. The chronic electrode assembly included an integrated silicon ribbon cable and percutaneous connector. In a consecutive series of six rats, 5/6 (83%) of the implanted microelectrodes recorded neuronal spike activity for more than six weeks, with four of the implants (66%) remaining functional for more than 28 weeks. In each animal, more than 80% of the electrode sites recorded spike activity over sequential recording sessions during the postoperative time period. These results provide a performance baseline to support further electrode system development for intracortical neural implant systems for medical applications.
Chronic Neural Recording Using Silicon-substrate Microelectrode Arrays Implanted in Cerebral Cortex
An important aspect of the development of cortical prostheses is the enhancement of suitable implantable microelectrode arrays for chronic neural recording. The objective of this study was to investigate the recording performance of silicon-substrate micromachined probes in terms of reliability and signal quality. These probes were found to consistently and reliably provide high-quality spike recordings over extended periods of time lasting up to 127 days. In a consecutive series of ten rodents involving 14 implanted probes, 13/14 (93%) of the devices remained functional throughout the assessment period. More than 90% of the probe sites consistently recorded spike activity with signal-to-noise ratios sufficient for amplitudes and waveform-based discrimination. Histological analysis of the tissue surrounding the probes generally indicated the development of a stable interface sufficient for sustained electrical contact. The results of this study demonstrate that these planar silicon probes are suitable for long-term recording in the cerebral cortex and provide an effective platform technology foundation for microscale intracortical neural interfaces for use in humans.
Integrated Microelectrode Array and Microfluidics for Temperature Clamp of Sensory Neurons in Culture
A device for cell culture is presented that combines MEMS technology and liquid-phase photolithography to create a microfluidic chip that influences and records electrical cellular activity. A photopolymer channel network is formed on top of a multichannel microelectrode array. Preliminary results indicated successful local thermal control within microfluidic channels and control of lamina position over the electrode array. To demonstrate the biological application of such a device, adult dissociated dorsal root ganglion neurons with a subpopulation of thermally-sensitive cells are attached onto the electrode array. Using laminar flow, dynamic control of local temperature of the neural cells was achieved while maintaining a constant chemical culture medium. Recording the expected altered cellular activity confirms the success of the integrated device.
Access to Trauma Centers in the United States
Previous studies have reported that the number and distribution of trauma centers are uneven across states, suggesting large differences in access to trauma center care.
Dynamic Control of Extracellular Environment in in Vitro Neural Recording Systems
A technique is presented for rapid fabrication of microfluidic channels on top of multichannel in vitro neural recording electrode arrays. The channels allow dynamic control of both stable and transient flow patterns over localized areas of the array, over biologically relevant timescales. A cellular model consisting of thermally sensitive dorsal root ganglion neurons was integrated into the devices. The device was used to demonstrate precise control of the extracellular microenvironment of individual cells on the array. Since the methods presented here are not specific to a particular cell type or neural recording system, the technique is amenable to a wide range of applications within the neuroscience field.
Multi-site Incorporation of Bioactive Matrices into MEMS-based Neural Probes
Methods are presented to incorporate polymer-based bioactive matrices into micro-fabricated implantable microelectrode arrays. Using simple techniques, hydrogels infused with bioactive molecules are deposited within wells in the substrate of the device. This method allows local drug delivery without increasing the footprint of the device. In addition, each well can be loaded individually, allowing spatial and temporal control over diffusion gradients in the microenvironment of the implanted neural interface probe. In vivo testing verified the following: diffusion of the bioactive molecules, integration of the bioactive molecules with the intended neural target and concurrent extracellular recording using nearby electrodes. These results support the feasibility of using polymer gels to deliver bioactive molecules to the region close to microelectrode shanks. This technique for microdrug delivery may serve as a means to intervene with the initial phases of the neuroinflammatory tissue response to permanently implanted microelectrode arrays.
Visualization of the Intact Interface Between Neural Tissue and Implanted Microelectrode Arrays
This research presents immunohistochemical strategies for assessing the interactions at the immediate interface between micro-scale implanted devices and the surrounding brain tissue during inflammatory astrogliotic reactions. This includes preparation, microscopy and analysis techniques for obtaining images of the intimate contact between neural cells and the surface of implantable micro-electromechanical systems (MEMS) devices. The ability to visualize the intact interface between an implant and the surrounding tissue allows researchers to examine tissue that is unchanged from its native implanted state. Conversely, current popular techniques involve removing the implant. This tends to cause damage to the tissue immediately surrounding the implant and can hinder one's ability to differentiate inflammatory responses to the implant versus physical damage occurring from removal of the implant from the tissue. Due to advances in microscopy and staining techniques, it is now possible to visualize the intact tissue-implant interface. This paper presents the development of imaging techniques for visualizing the intact interface between neural tissue and implanted devices. This is particularly important for understanding both the acute and chronic neuroinflammatory responses to devices intended for long-term use in a prosthetic system. Non-functional, unbonded devices were imaged in vitro and in vivo at different times post-implantation via a range of techniques. Using these techniques, detailed interactions could be seen between delicate cellular processes and the electrode surface, which would have been destroyed using conventional histology processes.
ECoG Factors Underlying Multimodal Control of a Brain-computer Interface
Most current brain-computer interface (BCI) systems for humans use electroencephalographic activity recorded from the scalp, and may be limited in many ways. Electrocorticography (ECoG) is believed to be a minimally-invasive alternative to electroencephalogram (EEG) for BCI systems, yielding superior signal characteristics that could allow rapid user training and faster communication rates. In addition, our preliminary results suggest that brain regions other than the sensorimotor cortex, such as auditory cortex, may be trained to control a BCI system using similar methods as those used to train motor regions of the brain. This could prove to be vital for users who have neurological disease, head trauma, or other conditions precluding the use of sensorimotor cortex for BCI control.
Rapid Prototyping of Patterned Poly-L-lysine Microstructures
For applications in cell biology, the ability to produce patterns of adhesion proteins for directing cell patterning is of particular interest. Often though, these patterns require extensive clean room facilities and intricate chrome masks to achieve very small feature sizes. We have developed a modified lift-off method for rapid prototyping of simple PLL structures that have features on a micron scale. The lift-off method is simple and easily adaptable to a variety of biological applications.
A Cortical Recording Platform Utilizing MicroECoG Electrode Arrays
Clinical applications of brain implantable devices for recording and interpreting electrical signals from the cortex have grown rapidly in the last decade. For long-term cortical recording, a micro-electrocorticographic (microECoG) electrode and universal platform were developed and evaluated. The electrode diameters and inter-electrode distances of the new device are on the order of 100s of microm, significantly smaller than general ECoG grids, and do not require penetrating the brain. Acute recordings from the device demonstrated that independent brain activity could be recorded from electrodes with a spatial resolution of 1 mm.
Complex Impedance Spectroscopy for Monitoring Tissue Responses to Inserted Neural Implants
A series of animal experiments was conducted to characterize changes in the complex impedance of chronically implanted electrodes in neural tissue. Consistent trends in impedance changes were observed across all animals, characterized as a general increase in the measured impedance magnitude at 1 kHz. Impedance changes reach a peak approximately 7 days post-implant. Reactive responses around individual electrodes were described using immuno- and histo-chemistry and confocal microscopy. These observations were compared to measured impedance changes. Several features of impedance changes were able to differentiate between confined and extensive histological reactions. In general, impedance magnitude at 1 kHz was significantly increased in extensive reactions, starting about 4 days post-implant. Electrodes with extensive reactions also displayed impedance spectra with a characteristic change at high frequencies. This change was manifested in the formation of a semi-circular arc in the Nyquist space, suggestive of increased cellular density in close proximity to the electrode site. These results suggest that changes in impedance spectra are directly influenced by cellular distributions around implanted electrodes over time and that impedance measurements may provide an online assessment of cellular reactions to implanted devices.
Microtechnology: Meet Neurobiology
The field of neuroscience has always been attractive to engineers. Neurons and their connections, like tiny circuit elements, process and transmit information in a dramatic way that is intimately curious to researchers in the computer science and engineering fields. Of particular interest has been the recent push in applying microtechnology to the field of neuroscience. This review is meant to provide an overview of some of the subtle nuances of the nervous system and outline recent advances in lab on a chip applications in neurobiology. It also aims to highlight some of the challenges the field faces in the hopes of encouraging new engineering researchers to collaborate with neurobiologists to help advance our basic understanding of the nervous system and create novel applications based on neuroengineering principles.
Electrocorticographically Controlled Brain-computer Interfaces Using Motor and Sensory Imagery in Patients with Temporary Subdural Electrode Implants. Report of Four Cases
Brain-computer interface (BCI) technology can offer individuals with severe motor disabilities greater independence and a higher quality of life. The BCI systems take recorded brain signals and translate them into real-time actions, for improved communication, movement, or perception. Four patient participants with a clinical need for intracranial electrocorticography (ECoG) participated in this study. The participants were trained over multiple sessions to use motor and/or auditory imagery to modulate their brain signals in order to control the movement of a computer cursor. Participants with electrodes over motor and/or sensory areas were able to achieve cursor control over 2 to 7 days of training. These findings indicate that sensory and other brain areas not previously considered ideal for ECoG-based control can provide additional channels of control that may be useful for a motor BCI.
Positioning and Guidance of Neurons on Gold Surfaces by Directed Assembly of Proteins Using Atomic Force Microscopy
We demonstrate that Atomic Force Microscopy nanolithography can be used to control effectively the adhesion, growth and interconnectivity of cortical neurons on Au surfaces. We demonstrate immobilization of neurons at well-defined locations on Au surfaces using two different types of patterned proteins: 1) poly-d-lysine (PDL), a positively charged polypeptide used extensively in tissue culture and 2) laminin, a component of the extracellular matrix. Our results show that both PDL and laminin patterns can be used to confine neuronal cells and to control their growth and interconnectivity on Au surfaces, a significant step towards the engineering of artificial neuronal assemblies with well-controlled neuron position and connections.
A Practical Procedure for Real-time Functional Mapping of Eloquent Cortex Using Electrocorticographic Signals in Humans
Functional mapping of eloquent cortex is often necessary prior to invasive brain surgery, but current techniques that derive this mapping have important limitations. In this article, we demonstrate the first comprehensive evaluation of a rapid, robust, and practical mapping system that uses passive recordings of electrocorticographic signals. This mapping procedure is based on the BCI2000 and SIGFRIED technologies that we have been developing over the past several years. In our study, we evaluated 10 patients with epilepsy from four different institutions and compared the results of our procedure with the results derived using electrical cortical stimulation (ECS) mapping. The results show that our procedure derives a functional motor cortical map in only a few minutes. They also show a substantial concurrence with the results derived using ECS mapping. Specifically, compared with ECS maps, a next-neighbor evaluation showed no false negatives, and only 0.46 and 1.10% false positives for hand and tongue maps, respectively. In summary, we demonstrate the first comprehensive evaluation of a practical and robust mapping procedure that could become a new tool for planning of invasive brain surgeries.
Massively Parallel Signal Processing Using the Graphics Processing Unit for Real-Time Brain-Computer Interface Feature Extraction
The clock speeds of modern computer processors have nearly plateaued in the past 5 years. Consequently, neural prosthetic systems that rely on processing large quantities of data in a short period of time face a bottleneck, in that it may not be possible to process all of the data recorded from an electrode array with high channel counts and bandwidth, such as electrocorticographic grids or other implantable systems. Therefore, in this study a method of using the processing capabilities of a graphics card [graphics processing unit (GPU)] was developed for real-time neural signal processing of a brain-computer interface (BCI). The NVIDIA CUDA system was used to offload processing to the GPU, which is capable of running many operations in parallel, potentially greatly increasing the speed of existing algorithms. The BCI system records many channels of data, which are processed and translated into a control signal, such as the movement of a computer cursor. This signal processing chain involves computing a matrix-matrix multiplication (i.e., a spatial filter), followed by calculating the power spectral density on every channel using an auto-regressive method, and finally classifying appropriate features for control. In this study, the first two computationally intensive steps were implemented on the GPU, and the speed was compared to both the current implementation and a central processing unit-based implementation that uses multi-threading. Significant performance gains were obtained with GPU processing: the current implementation processed 1000 channels of 250 ms in 933 ms, while the new GPU method took only 27 ms, an improvement of nearly 35 times.
Cortical Firing and Sleep Homeostasis
The need to sleep grows with the duration of wakefulness and dissipates with time spent asleep, a process called sleep homeostasis. What are the consequences of staying awake on brain cells, and why is sleep needed? Surprisingly, we do not know whether the firing of cortical neurons is affected by how long an animal has been awake or asleep. Here, we found that after sustained wakefulness cortical neurons fire at higher frequencies in all behavioral states. During early NREM sleep after sustained wakefulness, periods of population activity (ON) are short, frequent, and associated with synchronous firing, while periods of neuronal silence are long and frequent. After sustained sleep, firing rates and synchrony decrease, while the duration of ON periods increases. Changes in firing patterns in NREM sleep correlate with changes in slow-wave activity, a marker of sleep homeostasis. Thus, the systematic increase of firing during wakefulness is counterbalanced by staying asleep.
Flexible Thin Film Electrode Arrays for Minimally-invasive Neurological Monitoring
We present approaches for using thin film polymeric electrode arrays for use in applications of minimally invasive neurological monitoring. The flexibility and unique surface properties of the thin-film polyimide substrate in combination with a compact device platform make them amenable to a variety of surgical implantation procedures. Using a rapid-prototyping and fabrication technique, arrays of various geometries can be fabricated within a week. In this paper we test two different approaches for deploying electrode arrays through small cranial openings.
Evaluation of Micro-electrocorticographic Electrodes for Electrostimulation
Chronic neural recording and stimulation on the surface of the cortex with macroelectrodes has been shown to be promising for treating a wide range of neurological deficits. To enhance the specificity of these devices, dense arrangements of small area electrodes have been microfabricated for precise recording and control of neural populations. In this study micro-electrocorticographic (microECoG) electrodes were evaluated for electrostimulation. Surface modification with electrodeposited iridium oxide (EIrOx) resulted in lower impedance, higher charge carrying capacity, and lower, more linear voltage excursions during current controlled stimulation.
An Automated Microdroplet Passive Pumping Platform for High-speed and Packeted Microfluidic Flow Applications
Surface tension driven passive pumping is a microfluidic technology that uses the surface tension present in small droplets to generate flow. To enhance the potential of this type of passive pumping, a new 'micro passive pumping' technique has been developed that allows for high throughput fluidic delivery by combining passive pumping with a small droplet-based fluidic ejection system. Flow rates of up to four milliliters per minute (mL/min) were achieved that are solely limited by the channel geometry and droplet size. Fluid exchange rates can be performed within tens of milliseconds (ms) by delivering fluids from multiple nozzles. The technique can be extended to a multitude of platforms, as channels are not pressurized and therefore do not require bonding to a substrate. This technique provides a novel flow control for high-speed and packeted flow applications without requiring external tubing connections or substrate bonding.
A Microfluidic Brain Slice Perfusion Chamber for Multisite Recording Using Penetrating Electrodes
To analyze the spatiotemporal dynamics of network activity in a brain tissue slice, it is useful to record simultaneously from multiple locations. When obtained from laminar structures such as the hippocampus or neocortex, multisite recordings also yield information about subcellular current distributions via current source density analysis. Multisite probes developed for in vivo recordings could serve these purposes in vitro, allowing recordings to be obtained from brain slices at sites deeper within the tissue than currently available surface recording methods permit. However, existing recording chambers do not allow for the insertion of lamina-spanning probes that enter through the edges of brain slices. Here, we present a novel brain slice recording chamber design that accomplishes this goal. The device provides a stable microfluidic perfusion environment in which tissue health is optimized by superfusing both surfaces of the slice. Multichannel electrodes can be inserted parallel to the surface of the slice, at any depth relative to the surface. Access is also provided from above for the insertion of additional recording or stimulating electrodes. We illustrate the utility of this recording configuration by measuring current sources and sinks during theta burst stimuli that lead to the induction of long-term potentiation in hippocampal slices.
Precise Control over the Oxygen Conditions Within the Boyden Chamber Using a Microfabricated Insert
Cell migration is a hallmark of cancer cell metastasis and is highly correlated with hypoxia in tumors. The Boyden chamber is a porous membrane-based migration platform that has seen a great deal of use for both in vitro migration and invasion assays due to its adaptability to common culture vessels and relative ease of use. The hypoxic chamber is a current tool that can be implemented to investigate the cellular response to oxygen paradigms. Unfortunately, this method lacks the spatial and temporal precision to accurately model a number of physiological phenomena. In this article, we present a newly developed microfabricated polydimethylsiloxane (PDMS) device that easily adapts to the Boyden chamber, and provides more control over the oxygenation conditions exposed to cells. The device equilibrates to 1% oxygen in about 20 min, thus demonstrating the capabilities of a system for researchers to establish both short-term continuous and intermittent hypoxia regimes. A Parylene-C thin-film coating was used to prevent ambient air penetration through the bulk PDMS and was found to yield improved equilibration times and end-point concentrations. MDA-MD-231 cells, an invasive breast cancer line, were used as a model cell type to demonstrate the effect of oxygen concentration on cell migration through the Boyden chamber porous membrane. Continuous hypoxia downregulated migration of cells relative to the normoxic control, as did an intermittent hypoxia regime (IH) cycling between 0% and 21% oxygen (0-21% IH). However, cells exposed to 5-21% IH exhibited increased migration compared to the other conditions, as well as relative to the normoxic control. The results presented here show the device can be utilized for experiments implementing the Boyden chamber for in vitro hypoxic studies, allowing experiments to be conducted faster and with more precision than currently possible.
Functional Control of Transplantable Human ESC-derived Neurons Via Optogenetic Targeting
Current methods to examine and regulate the functional integration and plasticity of human ESC (hESC)-derived neurons are cumbersome and technically challenging. Here, we engineered hESCs and their derivatives to express the light-gated channelrhodopsin-2 (ChR2) protein to overcome these deficiencies. Optogenetic targeting of hESC-derived neurons with ChR2 linked to the mCherry fluorophore allowed reliable cell tracking as well as light-induced spiking at physiological frequencies. Optically induced excitatory and inhibitory postsynaptic currents could be elicited in either ChR2(+) or ChR2(-) neurons in vitro and in acute brain slices taken from transplanted severe combined immunodeficient (SCID) mice. Furthermore, we created a clonal hESC line that expresses ChR2-mCherry under the control of the synapsin-1 promoter. On neuronal differentiation, ChR2-mCherry expression was restricted to neurons and was stably expressed for at least 6 months, providing more predictable light-induced currents than transient infections. This pluripotent cell line will allow both in vitro and in vivo analysis of functional development as well as the integration capacity of neuronal populations for cell-replacement strategies.
Distance Dependence of Neuronal Growth on Nanopatterned Gold Surfaces
Understanding network development in the brain is of tremendous fundamental importance, but it is immensely challenging because of the complexity of both its architecture and function. The mechanisms of axonal navigation to target regions and the specific interactions with guidance factors such as membrane-bound proteins, chemical gradients, mechanical guidance cues, etc., are largely unknown. A current limitation for the study of neural network formation is the ability to control precisely the connectivity of small groups of neurons. A first step in designing such networks is to understand the "rules" central nervous system (CNS) neurons use to form functional connections with one another. Here we begin to delineate novel rules for growth and connectivity of small numbers of neurons patterned on Au substrates in simplified geometries. These studies yield new insights into the mechanisms determining the organizational features present in intact systems. We use a previously reported atomic force microscopy (AFM) nanolithography method to control precisely the location and growth of neurons on these surfaces. By examining a series of systems with different geometrical parameters, we quantitatively and systematically analyze how neuronal growth depends on these parameters.
Semiconductor Nanomembrane Tubes: Three-dimensional Confinement for Controlled Neurite Outgrowth
In many neural culture studies, neurite migration on a flat, open surface does not reflect the three-dimensional (3D) microenvironment in vivo. With that in mind, we fabricated arrays of semiconductor tubes using strained silicon (Si) and germanium (Ge) nanomembranes and employed them as a cell culture substrate for primary cortical neurons. Our experiments show that the SiGe substrate and the tube fabrication process are biologically viable for neuron cells. We also observe that neurons are attracted by the tube topography, even in the absence of adhesion factors, and can be guided to pass through the tubes during outgrowth. Coupled with selective seeding of individual neurons close to the tube opening, growth within a tube can be limited to a single axon. Furthermore, the tube feature resembles the natural myelin, both physically and electrically, and it is possible to control the tube diameter to be close to that of an axon, providing a confined 3D contact with the axon membrane and potentially insulating it from the extracellular solution.
Microfluidics-based Devices: New Tools for Studying Cancer and Cancer Stem Cell Migration
Cell movement is highly sensitive to stimuli from the extracellular matrix and media. Receptors on the plasma membrane in cells can activate signal transduction pathways that change the mechanical behavior of a cell by reorganizing motion-related organelles. Cancer cells change their migration mechanisms in response to different environments more robustly than noncancer cells. Therefore, therapeutic approaches to immobilize cancer cells via inhibition of the related signal transduction pathways rely on a better understanding of cell migration mechanisms. In recent years, engineers have been working with biologists to apply microfluidics technology to study cell migration. As opposed to conventional cultures on dishes, microfluidics deals with the manipulation of fluids that are geometrically constrained to a submillimeter scale. Such small scales offer a number of advantages including cost effectiveness, low consumption of reagents, high sensitivity, high spatiotemporal resolution, and laminar flow. Therefore, microfluidics has a potential as a new platform to study cell migration. In this review, we summarized recent progress on the application of microfluidics in cancer and other cell migration researches. These studies have enhanced our understanding of cell migration and cancer invasion as well as their responses to subtle variations in their microenvironment. We hope that this review will serve as an interdisciplinary guidance for both biologists and engineers as they further develop the microfluidic toolbox toward applications in cancer research.
A Micro-electrocorticography Platform and Deployment Strategies for Chronic BCI Applications
Over the past decade, electrocorticography (ECoG) has been used for a wide set of clinical and experimental applications. Recently, there have been efforts in the clinic to adapt traditional ECoG arrays to include smaller recording contacts and spacing. These devices, which may be collectively called "micro-ECoG" arrays, are loosely defined as intercranial devices that record brain electrical activity on the sub-millimeter scale. An extensible 3D-platform of thin film flexible micro-scale ECoG arrays appropriate for Brain-Computer Interface (BCI) application, as well as monitoring epileptic activity, is presented. The designs utilize flexible film electrodes to keep the array in place without applying significant pressure to the brain and to enable radial subcranial deployment of multiple electrodes from a single craniotomy. Deployment techniques were tested in non-human primates, and stimulus-evoked activity and spontaneous epileptic activity were recorded. Further tests in BCI and epilepsy applications will make the electrode platform ready for initial human testing.
Multiphoton Flow Cytometry to Assess Intrinsic and Extrinsic Fluorescence in Cellular Aggregates: Applications to Stem Cells
Detection and tracking of stem cell state are difficult due to insufficient means for rapidly screening cell state in a noninvasive manner. This challenge is compounded when stem cells are cultured in aggregates or three-dimensional (3D) constructs because living cells in this form are difficult to analyze without disrupting cellular contacts. Multiphoton laser scanning microscopy is uniquely suited to analyze 3D structures due to the broad tunability of excitation sources, deep sectioning capacity, and minimal phototoxicity but is throughput limited. A novel multiphoton fluorescence excitation flow cytometry (MPFC) instrument could be used to accurately probe cells in the interior of multicell aggregates or tissue constructs in an enhanced-throughput manner and measure corresponding fluorescent properties. By exciting endogenous fluorophores as intrinsic biomarkers or exciting extrinsic reporter molecules, the properties of cells in aggregates can be understood while the viable cellular aggregates are maintained. Here we introduce a first generation MPFC system and show appropriate speed and accuracy of image capture and measured fluorescence intensity, including intrinsic fluorescence intensity. Thus, this novel instrument enables rapid characterization of stem cells and corresponding aggregates in a noninvasive manner and could dramatically transform how stem cells are studied in the laboratory and utilized in the clinic.
An Inertia Enhanced Passive Pumping Mechanism for Fluid Flow in Microfluidic Devices
We describe and characterize a pumping mechanism that leverages the momentum present in small droplets ejected from a micro-nozzle to drive flow in an open microfluidic device. This approach allows driving flow in a microfluidic device in a regime that offers unique features different to those achievable with typical passive pumping or syringe-pump driven flow. Two flow regimes with specific flow characteristics are described: inertia enhanced passive pumping, in which fluid exchange times in the channel are significantly reduced, and inertia actuated flow, in which it is possible to initiate flow in an empty channel or against natural pressure gradients. Momentum is leveraged to create rapid fluid exchanges, instantaneous flow reversal, filling and mixing inside the microfluidic device.
Mental Workload During Brain-computer Interface Training
It is not well understood how people perceive the difficulty of performing brain-computer interface (BCI) tasks, which specific aspects of mental workload contribute the most, and whether there is a difference in perceived workload between participants who are able-bodied and disabled. This study evaluated mental workload using the NASA Task Load Index (TLX), a multi-dimensional rating procedure with six subscales: Mental Demands, Physical Demands, Temporal Demands, Performance, Effort, and Frustration. Able-bodied and motor disabled participants completed the survey after performing EEG-based BCI Fitts' law target acquisition and phrase spelling tasks. The NASA-TLX scores were similar for able-bodied and disabled participants. For example, overall workload scores (range 0-100) for 1D horizontal tasks were 48.5 (SD = 17.7) and 46.6 (SD 10.3), respectively. The TLX can be used to inform the design of BCIs that will have greater usability by evaluating subjective workload between BCI tasks, participant groups, and control modalities. PRACTITIONER SUMMARY: Mental workload of brain-computer interfaces (BCI) can be evaluated with the NASA Task Load Index (TLX). The TLX is an effective tool for comparing subjective workload between BCI tasks, participant groups (able-bodied and disabled), and control modalities. The data can inform the design of BCIs that will have greater usability.
Brain Slice on a Chip: Opportunities and Challenges of Applying Microfluidic Technology to Intact Tissues
Isolated brain tissue, especially brain slices, are valuable experimental tools for studying neuronal function at the network, cellular, synaptic, and single channel levels. Neuroscientists have refined the methods for preserving brain slice viability and function and converged on principles that strongly resemble the approach taken by engineers in developing microfluidic devices. With respect to brain slices, microfluidic technology may 1) overcome the traditional limitations of conventional interface and submerged slice chambers and improve oxygen/nutrient penetration into slices, 2) provide better spatiotemporal control over solution flow/drug delivery to specific slice regions, and 3) permit successful integration with modern optical and electrophysiological techniques. In this review, we highlight the unique advantages of microfluidic devices for in vitro brain slice research, describe recent advances in the integration of microfluidic devices with optical and electrophysiological instrumentation, and discuss clinical applications of microfluidic technology as applied to brain slices and other non-neuronal tissues. We hope that this review will serve as an interdisciplinary guide for both neuroscientists studying brain tissue in vitro and engineers as they further develop microfluidic chamber technology for neuroscience research.
