The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Retinal neuromodulation is an emerging therapeutic approach to restore functional vision to those suffering retinal photoreceptor degeneration. The retina encodes visual information and transmits it to the brain. Replicating this retinal code through electrical stimulation is essential to improving the performance of visual prostheses. In doing so, the first step relies on precise neural recordings...
A continuum multi-domain model of electrical stimulation of the retina is presented. Each point in the retinal ganglion cell layer could be thought of as representing a single cell, whose biophysics is described using a four-compartment formulation incorporating varying ion channel expressions in the soma, axon initial segment, dendrites and axon. Our continuum model was validated against a discrete...
Retinal neuroprostheses or ‘bionic eyes’, aim to restore patterned vision to those with vision loss by electrically stimulating the remaining neurons in the degenerate retina. Despite considerable progress over the last two decades, such devices generally stimulate indiscriminately both the ‘ON’ and ‘OFF’ visual pathways in the retina, conveying highly non-physiological signals to the brain.
Goal: Time–frequency analysis incorporating the wavelet transform followed by the principal component analysis (WT-PCA) has been a powerful approach for the analysis of biomedical signals, such as electromyography (EMG), electroencephalography, electrocardiography, and Doppler ultrasound. Time–frequency coefficients at various scales were usually transformed into a 1-D array using only a single or...
A retinal ganglion cell (RGC) model based on accurate biophysics and detailed representations of cell morphologies was used to understand how these cells respond to electrical stimulation over a wide range of frequencies, spanning 50–2000 pulses per second (PPS). Our modeling results and associated in vitro data both suggest the usefulness of high stimulation frequency in effectively modulating the...
Retinal ganglion cells (RGCs) in the vertebrate retina display a wide range of dendritic morphologies. In order to isolate the contribution of this physical property, we employed a neural morphology generator to study the differences in firing patterns among RGCs with different dendritic geometrical factors but with identical voltage-gated channel kinetics and distributions. Our results suggest that...
In this study, ON and OFF retinal ganglion cell (RGC) models based on accurate biophysics and realistic representations of cell morphologies were used to understand how these cells selectively respond to high-frequency electrical stimulation (HFS). With optimized model parameters and the incorporation of detailed cell morphologies, these two models were able to closely replicate experimental ON and...
Retinal ganglion cells (RGCs) demonstrate a large range of variation in their ionic channel properties and morphologies. These cell-specific properties are responsible for the unique way they process synaptic inputs. A cell-specific modeling approach allows us to examine the functional significance of regional membrane channel expression and cell morphology. ON and OFF RGC models based on accurate...
Active regional conductances and inhomogeneous distribution of membrane ionic channels in dendrites influence the integration of synaptic inputs in cortical neurons. How these properties shape the response properties of retinal ganglion cells (RGC) in the mammalian retina has remained largely unexplored. In this study, we used a morphologically-realistic RGC computational model to study how active...
We developed anatomically and biophysically detailed ionic models to understand how cell morphology contributes to the unique firing patterns of ON and OFF retinal ganglion cells (RGCs). With identical voltage-gated channel kinetics and distribution, cell morphology alone is sufficient to generate quantitatively distinct electrophysiological responses. Notably, recent experimental observations from...
Variations in ionic channel expression and anatomical properties can influence how different retinal ganglion cell (RGC) types process synaptic information. Computational modeling approaches allow us to precisely control these biophysical and physical properties and isolate their effects in shaping RGC firing patterns. In this study, three models based on realistic representations of RGC morphologies...
Generic ionic models optimized to replicate experimentally recorded cardiac action potentials (APs) from the central and peripheral sinoatrial node (SAN), the natural pacemaker of the heart, as well as atrial intact-myocytes are implemented in a realistic 2D model of rabbit SAN geometry. The model was used to investigate two frequently-proposed modes of SAN architecture: the gradient and mosaic hypotheses...
In this study, we used a novel missing currents technique to extend an existing conductance-based ionic current model of retinal ganglion cells (RGCs). The revised model reproduced a variety of biological behaviors. In particular, the model contains a hyperpolarization activated current (Ih). This model can effectively simulate the mechanisms underlying both normal and rebound action potentials. The...
A cardiac sino-atrial tissue model based on a simplified 2D disc geometry and a generic ionic model is described and optimized to fit intact-tissue microelectrode experimental recordings. Concentric regions were defined representing the central and peripheral sino-atrial node and the atrium, each with a unique set of ionic model parameters. Intracellular action potentials were recorded from the respective...
A multiple dataset model fitting approach for improving parameter reliability in action potential modeling is presented. A robust generic cardiac ionic model employing membrane currents based on two-gate Hodgkin-Huxley kinetics is described. Its generic nature allows it to accurately reproduce action potential waveforms in heterogeneous cardiac tissue by optimizing parameters governing ion channel...
A three-dimensional anatomically and electro-physiologically realistic model of atrial propagation is developed utilizing generic cardiac ionic models fitted to experimentally recorded action potentials (APs). The atrial geometry incorporated realistic wall thickness and twelve anatomical structures, including the sino-atrial node (SAN), pulmonary veins, interatrial septum, Bachmann's bundle and coronary...
A generic cardiac ionic model employing membrane currents based on two-gate Hodgkin-Huxley kinetics is presented. Its generic nature allows it to accurately reproduce action potential waveforms in heterogeneous cardiac tissue by optimizing parameters governing ion channel kinetics and magnitudes. The model allows a user-defined number of voltage and time-dependent ion currents to be incorporated,...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.