Geometry based dynamic modeling of the neuron-electrode interface

A dynamic model of the neuron-electrode interface is presented which is based on the interface geometry and the electrical properties of the neuronal membrane. The model is used to compute the potential at the electrode and the local membrane potentials. Extracellular as well as intracellular current stimulation can be simulated. The results demonstrate that extracellular recorded action potentials with several shapes and amplitudes can be produced, depending on the properties of the interface and the membrane. With homogeneous membrane properties, only small amplitudes are simulated, High amplitudes are produced with decreased concentration of voltage sensitive channels in the lower membrane. Resemblance of the shape of the intracellular potential is accomplished by decreasing the capacity of the lower membran

Triple leads with longitudinal guarded cathodes in spinal cord stimulation-effect of transversal lead separation

In spinal cord stimulation (SCS) clinical practice, longitudinal guarded cathode stimulation by a single lead, placed on the spinal cord midline provides the broadest parasthesia coverage. This study uses a triple lead longitudinal tripole with the center lead placed on the midline. The transversal spacing between the leads is varied to study its effect on the usage range (UR) and the recruited area (both depth and width) of dorsal colums activation

Finite element modeling of the neuron-electrode interface: stimulus transfer and geometry

The relation between stimulus transfer and the geometry of the neuron-electrode interface can not be determined properly using electrical equivalent circuits, since current that flows from the sealing gap through the neuronal membrane is difficult to model in these circuits. Therefore, finite element modeling is proposed as a tool for linking the electrical properties of the neuron-electrode interface to its geometr

Extracellular stimulation window explained by a geometry-based model of the neuron-electrode contact

Extracellular stimulation of single cultured neurons which are completely sealing a microelectrode is usually performed using anodic or biphasic currents of at least 200 nA. However, recently obtained experimental data demonstrate the possibility to stimulate a neuron using cathodic current pulses with less amplitude. Also, a stimulation window is observed. These findings can be explained by a finite-element model which permits geometry-based electrical representation of the neuron-electrode interface and can be used to explore the required conditions for extracellular stimulation in detail. Modulation of the voltage sensitive channels in the sealing part of the membrane appears to be the key to successful cathodic stimulation. Furthermore, the upper limit of the stimulation window can be explained as a normal consequence of the neuronal membrane electrophysiology

Geometry-based finite-element modeling of the electrical contact between a cultured neuron and a microelectrode

The electrical contact between a substrate embedded microelectrode and a cultured neuron depends on the geometry of the neuron-electrode interface. Interpretation and improvement of these contacts requires proper modeling of all coupling mechanisms. In literature, it is common practice to model the neuron-electrode contact using lumped circuits in which large simplifications are made in the representation of the interface geometry. In this paper, the finite-element method is used to model the neuron-electrode interface, which permits numerical solutions for a variety of interface geometries. The simulation results offer detailed spatial and temporal information about the combined electrical behavior of extracellular volume, electrode-electrolyte interface and neuronal membrane

The preferences, experience and level of comfort of anaesthetists in managing difficult intubation and ‘cannot intubate, cannot ventilate’ scenarios

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Medicine in Anaesthesiology. Johannesburg, 2016.Background: The “cannot intubate cannot ventilate” (CICV) scenario is a rare occurrence but can lead to significant morbidity and mortality if not managed appropriately. International data shows that anaesthetists lack knowledge of and fail to employ difficult airway algorithms. Method: A prospective, contextual, descriptive study was done to determine the preferences, experience and level of comfort of anaesthetists in the Wits Department of Anaesthesiology to manage difficult intubations and CICV situations. A previously validated questionnaire was adapted for local use and distributed to all available anaesthetists. Results: A total of 111 (88.1%) participants knew the location of the difficult airway trolley, but 43 (38.8%) stated that the trolley is not easily accessible. Ninety two (73%) participants preferred the videolaryngoscope as first choice device when facing a difficult airway. The predominant second choice devices were the flexible fibre-optic scope, chosen by 52 (43%) and the intubating laryngeal mask, chosen by 48 (38.1%). The majority of participants had no experience with the retrograde wire set, optical stylet and rigid bronchoscope. The most popular device for cricothyroidotomy, chosen by 47 (37.3%), was an IV cannula, but only 34.9% was comfortable with using this option. The majority of anaesthetists have no experience with the internationally recommended open surgical method. Sixty-three (50%) of the participants have experienced a CICV scenario in clinical practice. Conclusion: Airway training can be improved in our department. The location of the difficult airway trolley is not known by everyone and many believe that it is not readily available in an emergency. The videolaryngoscope is the preferred difficult airway device and the IV cannula the first choice in a CICV scenario. There is a significant difference in the comfort level of consultants and registrars with the use of most advanced airway devices.LG201

Modeled channel distributions explain extracellular recordings from cultured neurons sealed to microelectrodes

Amplitudes and shapes of extracellular recordings from single neurons cultured on a substrate embedded microelectrode depend not only on the volume conducting properties of the neuron-electrode interface, but might also depend on the distribution of voltage-sensitive channels over the neuronal membrane. In this paper, finite-element modeling is used to quantify the effect of these channel distributions on the neuron-electrode contact. Slight accumulation or depletion of voltage-sensitive channels in the sealing membrane of the neuron results in various shapes and amplitudes of simulated extracellular recordings. However, estimation of channel-specific accumulation factors from extracellular recordings can be obstructed by co-occuring ion currents and defect sealing. Experimental data from cultured neuron-electrode interfaces suggest depletion of sodium channels and accumulation of potassium channels

The effect of training of culture neuronal networks, can they learn

Dissociated 1 or 2 days old postnatal rat cortical cells were cultured onto multi electrode arrays (MEA’s) with 61 electrode sites. They were trained with two protocols, i.e. the tetanic stimulation method from the report by Jimbo et al. (1998) and the selective adaptation protocol (report Shahaf and Marom, 2001). Tetanic stimulation training changed the net- work response significiantly. But training had no lasting effect, which means no learning result. The selective adaptation proto- col did also not lead to lasting learning effects