Restoring the encoding properties of a stochastic neuron model by an exogenous noise

Here we evaluate the possibility of improving the encoding properties of an impaired neuronal system by superimposing an exogenous noise to an external electric stimulation signal. The approach is based on the use of mathematical neuron models consisting of stochastic HH-like circuit, where the impairment of the endogenous presynaptic inputs is described as a subthreshold injected current and the exogenous stimulation signal is a sinusoidal voltage perturbation across the membrane. Our results indicate that a correlated Gaussian noise, added to the sinusoidal signal can significantly increase the encoding properties of the impaired system, through the Stochastic Resonance (SR) phenomenon. These results suggest that an exogenous noise, suitably tailored, could improve the efficacy of those stimulation techniques used in neuronal systems, where the presynaptic sensory neurons are impaired and have to be artificially bypassed

Numerical characterization of intraoperative and chronic electrodes in deep brain stimulation

An intraoperative electrode (microelectrode) is used in the deep bra In stImulation (DBS) technique to pinpoint the brain target and to choose the best parameters for the electrical stimulus. However, when the intraoperative electrode is replaced with the chronic one (macroelectrode), the observed effects do not always coincide with predictions. To investigate the causes of such discrepancies, a 3D model of the basal ganglia has been considered and realistic models of both intraoperative and chronic electrodes have been developed and numerically solved. Results of simulations of the electric potential (V) and the activating function (AF) along neuronal fibers show that the different geometries and sizes of the two electrodes do not change the distributions and polarities of these functions, but rather the amplitudes. This effect is similar to the one produced by the presence of different tissue layers (edema or glial tissue) in the pen-electrode space. Conversely, an inaccurate positioning of the chronic electrode with respect to the intraoperative one (electric centers not coincident) may induce a completely different electric stimulation in some groups of fibers

Improved 2D-FDTD method for TWFET bandwidth characterization

A new 2D-FDTD method has been proposed to analyze the dispersion diagram of planar circuits. Traveling wave field effect transistor (TWFET) is a solid state device designed to amplify signals over a wide bandwidth. An analysis of the passive behavior of this device has been performed using mode-matching technique and assuming that the passive structure performances are affected only by the width of the T bar of the gate electrode. To verify such hypothesis and to determine the cut-off frequency of the higher order modes that limits its bandwidth, we have simplified the 2D-FDTD method with a particular normalization, that permits the analysis of the case β=0. The proposed approach was tested calculating the dispersion for some known structures and it has been used in the TWFET characterization

A new wire patch cell for the exposure of cell cultures to electromagnetic fields at 2.45 GHz: Design and numerical characterization

Studies on the interaction between electromagnetic (EM) fields and biological systems have recently gathered further momentum due to the huge diffusion of wireless networks. In order to investigate possible effects on cultured cells of EM fields, in the frequency range typical of such a kind of communication, an in vitro exposure system has been designed and numerically characterized. The system is a Wire Patch Cell (WPC) operating at 2.45 GHz which enables the contemporary exposure of four 35 mm Petri dishes and can be inserted into a commercial incubator. Numerical dosimetry has been carried out by means of the CST Microwave Studio® simulator. Results indicate a good efficiency, in terms of Specific Absorption Rate (SAR) in the biological sample per 1 W of input power. Moreover, the homogeneity of the SAR distribution inside each Petri dish is around 70%, considered an acceptable value for such a kind of biological experimentsStudies on the interaction between electromagnetic (EM) fields and biological systems have recently gathered further momentum due to the huge diffusion of wireless networks. In order to investigate possible effects on cultured cells of EM fields, in the frequency range typical of such a kind of communication, an in vitro exposure system has been designed and numerically characterized. The system is a Wire Patch Cell (WPC) operating at 2.45 GHz which enables the contemporary exposure of four 35 mm Petri dishes and can be inserted into a commercial incubator. Numerical dosimetry has been carried out by means of the CST Microwave Studio ® simulator. Results indicate a good efficiency, in terms of Specific Absorption Rate (SAR) in the biological sample per 1 W of input power. Moreover, the homogeneity of the SAR distribution inside each Petri dish is around 70%, considered an acceptable value for such a kind of biological experiments