Search results for "Microelectrodes"

Selection of the Optimal Algorithm for Real-Time Estimation of Beta Band Power during DBS Surgeries in Patients with Parkinson's Disease

2017

Deep Brain Stimulation (DBS) is a surgical procedure for the treatment of motor disorders in patients with Parkinson’s Disease (PD). DBS involves the application of controlled electrical stimuli to a given brain structure. The implantation of the electrodes for DBS is performed by a minimally invasive stereotactic surgery where neuroimaging and microelectrode recordings (MER) are used to locate the target brain structure. The Subthalamic Nucleus (STN) is often chosen for the implantation of stimulation electrodes in DBS therapy. During the surgery, an intraoperative validation is performed to locate the dorsolateral region of STN. Patients with PD reveal a high power in the β band (frequenc…

Analyzing the feasibility of time correlated spectral entropy for the assessment of neuronal synchrony

2016

In this paper, we study neuronal network analysis based on microelectrode measurements. We search for potential relations between time correlated changes in spectral distributions and synchrony for neuronal network activity. Spectral distribution is quantified by spectral entropy as a measure of uniformity/complexity and this measure is calculated as a function of time for the recorded neuronal signals, i.e., time variant spectral entropy. Time variant correlations in the spectral distributions between different parts of a neuronal network, i.e., of concurrent measurements via different microelectrodes, are calculated to express the relation with a single scalar. We demonstrate these relati…

Posterior cordotomy in bilateral vocal cord paralysis using monopolar microelectrodes and radiofrequency in 18 patient

2017

Calibration of misonidazole labeling by simultaneous measurement of oxygen tension and labeling density in multicellular spheroids

1995

To correlate misonidazole concentrations and oxygen pressures (Po2) at identical locations within EMT6/Ro multi-cell spheroids (mean diameters +/- SD: 867 +/- 20 microns), Po2 measurements were performed with oxygen-sensitive microelectrodes during incubation of these spheroids with tritiated misonidazole (10 mg/I; 445 microCi/mg). In each individual spheroid, Po2 profiles were correlated with the corresponding spatial distribution of misonidazole as quantified by conventional autoradiography and grain counting. To compare the oxygenation status of spheroids in the measuring chamber with that of spheroids in spinner culture, misonidazole labeling was performed in both environments following…

Diffusion in slice preparations bathed in unstirred solutions

1987

A diffusion model is described here, which allows for the estimations of drug concentration changes in porous media, such as in slice tissues of the central nervous system (CNS) bathed in unstirred solutions following abrupt changes of drug concentration. This model may be used for the interpretation of data obtained in neuropharmacological studies if (i) the diffusion coefficient of the molecules under investigation is constant within the excised tissue, (ii) drug molecules are diffusing only in the extracellular space (ECS) and are not bound by the tissue, (iii) drug molecules diffuse mainly within one dimension, (iv) the drug concentration in the bath is changed within 5 s, and (v) the b…

Performance of interdigitated nanoelectrodes for electrochemical DNA biosensor.

2003

An electrochemical methodology for bio-molecule sensing using an array of well-defined nanostructures is presented. We describe the fabrication by e-beam lithography of nanoelectrodes consisting of a 100 micro m x 50 micro m area containing interdigitated electrodes of 100 nm in width and interelectrode distance of 200 nm. Sensitivity and response time of the nanoelectrodes are compared to the responses of macro- and microelectrodes. The specificity of the sensor is studied by modifying the gold electrodes with DNA. The technique enables to characterize both single and double-stranded DNA of 15 nucleotides. A special electrochemical cell is adapted to control the temperature and measure the…

Quantification and automatized adaptive detection of in vivo and in vitro neuronal bursts based on signal complexity.

2015

In this paper, we propose employing entropy values to quantify action potential bursts in electrophysiological measurements from the brain and neuronal cultures. Conventionally in the electrophysiological signal analysis, bursts are quantified by means of conventional measures such as their durations, and number of spikes in bursts. Here our main aim is to device metrics for burst quantification to provide for enhanced burst characterization. Entropy is a widely employed measure to quantify regularity/complexity of time series. Specifically, we investigate the applicability and differences of spectral entropy and sample entropy in the quantification of bursts in in vivo rat hippocampal meas…

A stepper motor-driven microelectrode positioner

1987

The mechanical elements and the electronic control system from a stepper motor-driven microelectrode positioner is described. The unit embodies a high-precision small step angle hybrid motor. The compact, rugged and totally concentric design of the mechanic, by a spindle mechanism achieves the necessary precision by translating the stepwise rotations of the motor into steps of linear movement. The system takes advantage of commercially available low friction parts such as ball bearings, ball bushings and axles with hardened surfaces. The related electronic control unit is designed around the most recent integrated circuitry which is both sophisticated and economical. Though the described sy…

Carbon nanotubes as electrodes for dielectrophoresis of DNA

2006

Dielectrophoresis can potentially be used as an efficient trapping tool in the fabrication of molecular devices. For nanoscale objects, however, the Brownian motion poses a challenge. We show that the use of carbon nanotube electrodes makes it possible to apply relatively low trapping voltages and still achieve high enough field gradients for trapping nanoscale objects, e.g., single molecules. We compare the efficiency and other characteristics of dielectrophoresis between carbon nanotube electrodes and lithographically fabricated metallic electrodes, in the case of trapping nanoscale DNA molecules. The results are analyzed using finite element method simulations and reveal information abou…

Dorsal root ganglia neurite outgrowth measured as a function of changes in microelectrode array resistance

2017

Current research in prosthetic device design aims to mimic natural movements using a feedback system that connects to the patient's own nerves to control the device. The first step in using neurons to control motion is to make and maintain contact between neurons and the feedback sensors. Therefore, the goal of this project was to determine if changes in electrode resistance could be detected when a neuron extended a neurite to contact a sensor. Dorsal root ganglia (DRG) were harvested from chick embryos and cultured on a collagen-coated carbon nanotube microelectrode array for two days. The DRG were seeded along one side of the array so the processes extended across the array, contacting a…