Revealing spectrum features of stochastic neuron spike trains

Power spectra of spike trains reveal important properties of neuronal behavior. They exhibit several peaks, whose shape and position depend on applied stimuli and intrinsic biophysical properties, such as input current density and channel noise. The position of the spectral peaks in the frequency domain is not straightforwardly predictable from statistical averages of the interspike intervals, especially when stochastic behavior prevails. In this work, we provide a model for the neuronal power spectrum, obtained from Discrete Fourier Transform and expressed as a series of expected value of sinusoidal terms. The first term of the series allows us to estimate the frequencies of the spectral peaks to a maximum error of a few Hz, and to interpret why they are not harmonics of the first peak frequency. Thus, the simple expression of the proposed power spectral density (PSD) model makes it a powerful interpretative tool of PSD shape, and also useful for neurophysiological studies aimed at extracting information on neuronal behavior from spike train spectra

A consensus panel review of central nervous system effects of the exposure to low-intensity extremely low-frequency magnetic fields

BACKGROUND: A large number of studies explored the biological effects of extremely low-frequency (0-300 Hz) magnetic fields (ELF-MFs) on nervous system both at cellular and at system level in the intact human brain reporting several functional changes. However, the results of different studies are quite variable and the mechanisms of action of ELF-MFs are still poorly defined. The aim of this paper is to provide a comprehensive review of the effects of ELF-MFs on nervous system. METHODS: We convened a workgroup of researchers in the field to review and discuss the available data about the nervous system effects produced by the exposure to ELF-MFs. MAIN FINDINGS/DISCUSSION: We reviewed several methodological, experimental and clinical studies and discussed the findings in five sections. The first section analyses the devices used for ELF-MF exposure. The second section reviews the contribution of the computational methods and models for investigating the interaction between ELF-MFs and neuronal systems. The third section analyses the experimental data at cellular and tissue level showing the effects on cell membrane receptors and intracellular signaling and their correlation with neural stem cell proliferation and differentiation. The fourth section reviews the studies performed in the intact human brain evaluating the changes produced by ELF-MFs using neurophysiological and neuropsychological methods. The last section shows the limits and shortcomings of the available data, evidences the key challenges in the field and tracks directions for future research

3D microdosimetric model to plan and control in vitro drug delivery mediated by nsPEFs with GCPW system

Nanosecond pulsed electric fields (nsPEFs) with their wide frequency content, are recently known to be able to interact with cellular and subcellular membranes inducing reversible membrane permeabilization for biomedical applications. To improve treatments efficacy, lipid vesicles are studied and designed as smart delivery system able to respond to nsPEFs. In this work, authors report the study of an experimental bench suitable for in vitro exposure of cells and liposome nanocarriers to nsPEFs, compliant with the wideband requirements for nanosecond pulses. A multiphysics modelling able to predict cell and liposome nanoelectroporation is proposed to define the characteristics of signals to be used in experiments

Experimental characterization of a figure of eight coil for transcranial magnetic stimulation

In order to accurately evaluate the induced E field distribution inside the brain due to a transcranial magnetic stimulation (TMS) procedure, a complete characterization of the stimulating source is needed. In this paper, a full experimental characterization of a typical TMS coil is given, providing spatial distribution of the generated B field as well as input impedance and waveform of the current. Measurements show a slight deviation in the field distribution with respect to the one coming from idealized coil models, particularly for what concerns symmetry

Broadband coplanar system for in vitro experiments

A coplanar broadband and efficient system was developed for real-time exposure of in vitro neuronal samples to electromagnetic fields in the microwave range to test their effectiveness in nervous stimulation

Characterization of a portable and low cost system for practical dielectric spectroscopy

A portable setup for measurements of complex permittivity based on ad-hoc arrangements is proposed and its performance compared to the ones of a bench system. The measurement setup consists of a portable spectrum analyzer (used as vector network analyzer, VNA) connected to an open-end coaxial cable for S 11 acquisition. Scattering parameters were processed using custom Labview software specifically developed to obtain complex permittivity of liquids and soft materials in real-time. A suitable calibration procedure, based on a differential principle, enables accurate measurements. Raw results showed that the portable setup provides noisier traces if compared to the performance of a high precision laboratory VNA. However, accurate permittivity data have been achieved introducing filtering to eliminate signal oscillations and spurious noise without loss of information associated to liquid dielectric relaxations. This procedure, applied to standard liquids (ethanol, ethanediol, 2-propanol) showed good performance in terms of bias and precision. Water solutions, used for cell culturing purposes, both conductive and non-conductive, were also successfully measured. The obtained results are a proof of concept that the proposed procedure is a reliable technique to perform fast, low-cost and on site permittivity measurements, useful for diagnostic or therapeutic applications