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Many applications of neural stimulation demand a high current density from the electrodes used for stimulus delivery. New materials have been searched that can provide such large current and charge densities where the traditional noble metal and capacitor electrodes are inadequate. Titanium nitride, which has been used in cardiac pacemaker leads for many years, is one of these materials recently considered...
A new transient finite element model of extracellular action potentials recording with a microelectrode in a tissue slice is presented. The neuron model is based on the Hodgkin-Huxley equations implemented with a thin film approximation of the neuron membrane. The computations of the membrane potential and currents, as well as that of the intra and extracellular potential fields, are performed at...
Brain-machine interfaces (BMIs) have shown promise in augmenting people's control of their surroundings, especially for those suffering from paralysis due to neurological disorders. This paper describes an experiment using the rodent model to explore information available in neural signals recorded from chronically implanted intracortical microelectrode arrays. In offline experiments, a number of...
This paper reports the design of a battery-operated, high bandwidth, multi-channel wireless medical telemetry system. The system is capable of transmitting 2.3 Mbps of raw streaming data using the IEEE 802.11b protocol. In a typical application, the system was used to collect data from micro-wire electrodes implanted in the ventral striatum of an awake and behaving rat. The complete system weighs...
For pt.I see ibid., p.Z004024-7. Stimulation of the diseased retina via an intraocular electrode array is a proposed means of restoring some vision to the profoundly blind. A prosthetic device to this end would involve post-implantation calibration (analogous to cochlear implant fitting), wherein the subject indicates those discrete positions in the visual field where luminous percepts are elicited...
We describe a two-frequency diffuse optical tomographic (DOT) imaging and EEG recording system suitable for the study of real-time hemodynamic and neural activities in freely moving rats. The system uses a bundle of 16 optical fibers that both deliver light and capture its reemission. This bundle runs in parallel with a cable carrying EEG signals from 16 microelectrodes. Both data collection arrays...
As a method of observing regeneration of damaged nerves, research is being conducted on analyzing the electric signals of nerve fibers that are damaged and regenerating by implanting a microelectrode array between those nerves. Microelectrode arrays possess high impedance and a unique phase characteristic according to their structural features, thus it requires a phase linearity test and an impedance...
The objective of this study was to extract voluntary motor signals from the rubrospinal tract in behaving rats and study the correlation between these volitional signals and the elbow movements. Multi-contact silicone substrate surface electrodes were implanted chronically at the cervical C5-C6 and C6-C7 levels of the spinal cord. Recordings were made during face cleaning by the animal as this task...
The design of metal microelectrodes that produce minimal damage to tissue and can successfully record from and stimulate targeted neural structures necessitates a thorough understanding of the electrical phenomena generated in the tissue surrounding the electrodes. Computational modeling has been a primary strategy used to study these phenomena, and the Finite Element Method has proven to be a powerful...
Sensor arrays for the measurement of the load condition of polyethylene spacers in the total knee arthroplasty (TKA) prosthesis have been developed. Arrays of capacitive sensors are used to determine the three-dimensional strain within the polyethylene prosthesis component. Data from these sensors can be used to give researchers better understanding of component motion, loading, and wear phenomena...
A 64-channel neural processor has been developed for use in an implantable neural recording microsystem. In the scan mode, the processor is capable of detecting positive, negative, and biphasic spikes with programmable thresholds. It collects action potential information from the input channels, tags the activities with the associated channel address, compresses and finally packs the activity information...
Capacitive coupling within high-density microelectrode arrays can degrade neural recording signal or disperse neural stimulation current. Material deterioration in a chronically implanted neural stimulation/recording system can cause such an undesired effect. We present a simple method with an iterative algorithm to quantify the cross-coupling capacitance, in-situ
Characterizing the encapsulation layer caused by glial scar formation surrounding microelectrode arrays in chronic implants has been the subject of extensive research. Typically, an equivalent circuit model is used to characterize the reactive tissue response by nonlinearly fitting the electrical impedance spectroscopy (EIS) data. This model assumes a time invariant adjacent layer of encapsulation...
Intracortical microelectrode recordings of neural activity show great promise as control signals for neuroprosthetic applications. However, faithful, consistent recording of single unit spiking activity with chronically implanted silicon-substrate microelectrode arrays has proven difficult. Many approaches seek to enhance the long-term performance of microelectrode arrays by, for example, increasing...
This paper reports the design, fabrication and simulation of a novel array of micromachined electrodes with different lengths for use in auditory nerve prostheses. A 10times10 array is created in a 1 mm 2 on silicon with bulk micromachining technology. The electrode lengths vary from 200 mum to 400 mum. This design could provide access to most fascicles within the auditory nerve and thus allow stimulation...
Studies examining traumatic brain injury have suggested a 'window of opportunity' exists for therapeutic agents to mitigate edema and cellular toxicity effectively. However, successful therapy also relies on identifying the extent of blood-brain barrier disruption, which is associated with excessive extra-cellular concentrations of ions, excitatory amino acids, and serum proteins. The following study...
We present a monolithic microelectronic multichannel amplifier designed to facilitate measurements from multi-electrode arrays. A single silicon chip includes sixteen electrode amplifiers, along with interface and control circuitry to allow data collection through a compact 4-wire interface
One requirement of a chronically implantable, wireless neural interface device is the integration of electronic circuitry with the microelectrode array. Since the electronic IC dissipates a certain amount of power, it will affect the temperature in the tissues surrounding the implant site. In this paper, the thermal influence of an integrated, 3-dimensional Utah electrode array, to be implanted in...
Typically intracortical electrodes are required to puncture the intact pia mater during insertion which in the process can lead to brain dimpling and trauma. Furthermore, there is interest in the development of more flexible substrates to reduce relative micromotion after implantation, but such device have difficulty penetrating the pia without buckling. In this paper a strategy for reducing the mechanical...
Neuroscientists have widely used metal microelectrodes inserted into the cortex to record neural signals from, and provide electrical stimulation to, neural tissue for many years. Recently, the demand for implanting electrode arrays within the cortex, for both stimulation and recording, has rapidly increased. We are developing Active-floating-micro-electrode-arrays (AFMA) that are intended for use...
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