Leonel E Medina

University of Santiago, Chile | USACH · Departamento de Ingeniería Informática

Significance Sensory neuroprostheses offer the promise of restoring perceptual function to people with impaired sensation. Here, we developed a paradigm using intracortical microstimulation (ICMS) for encoding the sensation of fingertip motion against texture. Monkeys learned to interpret time-varying ICMS patterns, evoked by the interplay of their...

Alzheimer’s disease (AD) is one of the most significant health challenges of our time, affecting a growing number of the elderly population. In recent years, the retina has received increased attention as a candidate for AD biomarkers since it appears to manifest the pathological signatures of the disease. Therefore, its electrical activity may hin...

The interferential current (IFC) therapy is a noninvasive electrical neurostimulation technique intended to activate deep neurons using surface electrodes. In IFC, two independent kilohertz-frequency currents purportedly intersect where an interference field is generated. However, the effects of IFC on neurons within and outside the interference fi...

Objective. Our main goal was to determine the conditions for which a more precise calculation of the electric potential than the quasi-static approximation may be needed in models of electrical neurostimulation, particularly for signals with kilohertz-frequency components. Approach. We conducted a comprehensive quantitative study of the differences...

This paper studies the phenomenon of conduction block in model neurons using high-frequency biphasic stimulation (HFBS). The focus is investigating the triggering of undesired onset action potentials when the HFBS is turned on. The approach analyzes the transient behavior of an averaged system corresponding to the FitzHugh–Nagumo neuron model using...

This paper studies the phenomenon of conduction block in model neurons using high-frequency biphasic stimulation (HFBS). The focus is investigating the triggering of undesired onset action potentials when the HFBS is turned on. The approach analyzes the transient behavior of an averaged system corresponding to the FitzHugh-Nagumo neuron model using...

Objective. Our goal was to determine the conditions for which a more precise calculation of the electric potential than the quasi-static approximation may be needed in models of electrical neurostimulation, particularly for signals with kilohertz-frequency components. Approach. We conducted a comprehensive quantitative study of the differences in n...

The use of high-frequency currents in neurostimulation has received increased attention in recent years due to its varied effects on tissues and cells. Neurons are commonly modeled as nonlinear systems, and questions such as stability can thus be addressed with well-known averaging methods. A recent strategy called interferential currents uses elec...

The interferential current (IFC) therapy is a noninvasive electrical neurostimulation technique intended to activate deep neurons using surface electrodes. In IFC, two independent kilohertz-frequency currents purportedly intersect where an interference field is generated. However, the effects of IFC on neurons within and outside the interference fi...

Alzheimer's disease (AD) is one of the most significant health challenges of our time, affecting a growing number of the elderly population. In recent years, the retina has received increased attention as a candidate for AD biomarkers since it appears to manifest the pathological signatures of the disease. Therefore, its electrical activity may hin...

Intracortical microstimulation (ICMS) of the primary somatosensory cortex (S1) can produce percepts that mimic somatic sensation and thus has potential as an approach to sensorize prosthetic limbs. However, it is not known whether ICMS could recreate active texture exploration-the ability to infer information about object texture by using one′s fin...

Background Incorporating kilohertz-frequency signals in transcutaneous electrical stimulation has been proposed as a means to overcome the impedance of the skin, thereby reaching deeper nerves. In particular, a transdermal amplitude modulated signal (TAMS), composed of a 210 kHz non-zero offset carrier modulated by rectangular pulses, was introduce...

Objective: Models of excitable cells consider the membrane specific capacitance as a ubiquitous and constant parameter. However, experimental measurements show that the membrane capacitance declines with increasing frequency, i.e., exhibits dispersion. We quantified the effects of frequency-dependent membrane capacitance, c(f), on the excitability...

Transcutaneous electrical stimulation (TES) of nerve fibers may be optimized by overcoming the impedance of the skin using high-frequency (HF) stimulation signals. The excitation properties of nerve fibers depend on the spatiotemporal distribution of the extracellular field, and therefore quantifying the potentials during HF-TES is warranted. We pr...

The annual Computational Neuroscience Meeting (CNS) began in 1990 as a small workshop called Analysis and Modeling of Neural Systems. The goal of the workshop was to explore the boundary between neuroscience and computation. Riding on the success of several seminal papers, physicists had made "Neural Networks" fashionable, and soon the quantitative...

Objective: Incorporating high-frequency components in transcutaneous electrical stimulation (TES) waveforms may make it possible to stimulate deeper nerve fibers since the impedance of tissue declines with increasing frequency. However, the mechanisms of high-frequency TES remain largely unexplored. We investigated the properties of TES with frequ...

Electrical stimulation of peripheral nerves is a widespread technique for the treatment of neurological diseases and disorders. However, peripheral stimulation typically requires surgical implantation of an electrode and a pulse generator. Transcutaneous stimulation with an external electrode and pulse generator could provide a noninvasive alternat...

Artificial sensation via electrical or optical stimulation of brain sensory areas offers a promising treatment for sensory deficits. For a brain-machine-brain interface, such artificial sensation conveys feedback signals from a sensorized prosthetic limb. The ways neural tissue can be stimulated to evoke artificial sensation and the parameter space...

In mining, rock classification plays a crucial role at different stages of the extraction process ranging from the design of the mine to mineral grading and plant control. In this paper we present a new method to improve rock classification using digital image analysis, feature selection based on mutual information and a voting process to take into...

The tactile sense is being used in a variety of applications involving tactile human-machine interfaces. In a significant number of publications the classical threshold concept plays a central role in modelling and explaining psychophysical experimental results such as in stochastic resonance (SR) phenomena. In SR, noise enhances detection of sub-t...

Stochastic resonance (SR) is the counterintuitive phenomenon in which noise enhances detection of sub-threshold stimuli. The SR psychophysical threshold theory establishes that the required amplitude to exceed the sensory threshold barrier can be reached by adding noise to a sub-threshold stimulus. The aim of this study was to test the SR theory by...

El sentido del tacto ha sido usado en una diversidad de aplicaciones tales como la telecirugía, la robótica y la realidad virtual, entre otras. En la última década han surgido aplicaciones en que la adición de vibraciones mecánicas aleatorias (ruido táctil) permite mejorar la percepción de peque-ños estímulos táctiles. Este fenómeno, denominado res...

This paper compares the classification performance of linear-system- and neural-network-based models in handwritten-digit classification and face recognition. In inputs to a linear classifier, nonlinear inputs are generated based on linear inputs, using different forms of generating products. Using a genetic algorithm, linear and nonlinear inputs t...