Two Channel Electronic Device for Cortical Stimulations by Microampere DC Currents (original) (raw)
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Journal of Neuroscience Methods, 2008
A current source for neural stimulation is presented which converts arbitrary voltage signals to currentcontrolled signals while regulating the offset-voltage across the stimulation electrodes in order to keep the electrodes in an electrochemical state that allows for injecting a maximum charge. The offset-voltage can either be set to 0 V or to a bias-voltage, e.g. of a few 100 mV, as it can be advantageous for fully exploiting the charge injection capacity of iridium oxide electrodes.
Modular Current Stimulation System for Pre-clinical Studies
Frontiers in Neuroscience, 2020
Electric stimulators with precise and reliable outputs are an indispensable part of electrophysiological research. From single cells to deep brain or neuromuscular tissue, there are diverse targets for electrical stimulation. Even though commercial systems are available, we state the need for a low-cost, high precision, functional, and modular (hardware, firmware, and software) current stimulation system with the capacity to generate stable and complex waveforms for pre-clinical research. The system presented in this study is a USB controlled 4-channel modular current stimulator that can be expanded and generate biphasic arbitrary waveforms with 16-bit resolution, high temporal precision (µs), and passive charge balancing: the NES STiM (Neuro Electronic Systems Stimulator). We present a detailed description of the system's structural design, the controlling software, reliability test, and the pre-clinical studies [deep brain stimulation (DBS) in hemi-PD rat model] in which it was utilized. The NES STiM has been tested with MacOS and Windows operating systems. Interfaces to MATLAB source codes are provided. The system is inexpensive, relatively easy to build and can be assembled quickly. We hope that the NES STiM will be used in a wide variety of neurological applications such as Functional Electrical Stimulation (FES), DBS and closed loop neurophysiological research.
Transcranial Current Brain Stimulation (tCS): Models and Technologies
In this paper, we provide a broad overview of models and technologies pertaining to transcranial current brain stimulation (tCS), a family of related noninvasive techniques including direct current (tDCS), alternating current (tACS), and random noise current stimulation (tRNS). These techniques are based on the delivery of weak currents through the scalp (with electrode current intensity to area ratios of about 0.3-5 A/m ) at low frequencies (typically 1kHz) resulting in weak electric fields in the brain (with amplitudes of about 0.2-2 V/m). Here we review the biophysics and simulation of noninvasive, current-controlled generation of electric fields in the human brain and the models for the interaction of these electric fields with neurons, including a survey of in vitro and in vivo related studies. Finally, we outline directions for future fundamental and technological research.
2010 Biomedical Circuits and Systems Conference (BioCAS), 2010
Active control over the electric field distribution during deep brain stimulation (DBS) can provide better focus of the stimulation field on target regions, beneficial to improve neural selectivity and reduce side effects arising from simulation of non-target regions. A current-steering tripolar electrode configuration can be adopted to achieve better selectivity in DBS. The tripole consists of a central cathode and two lateral anodes. The currents through the anodes are set by two complementary current sources. By varying the ratio between the amplitude of the anodic currents, the current can be steered toward one anode, while keeping the cathodic current constant. In this paper we present the design of a current-steering tripolar current source in 0.35 m CMOS technology. The current source is capable of delivering cathodic currents up to 1.5mA and generate exponential and quasi-trapezoidal pulses needed for anodal blocking. The average mismatch between sourcing and sinking currents is in the order of 0.4% and the output compliance ranges between 6.1V and 11.15V for a 12V supply, when the maximum and minimum anodic currents are supplied, respectively.
The Journal of Ect, 2010
The use of noninvasive cortical electrical stimulation with weak currents has significantly increased in basic and clinical human studies. Initial, preliminary studies with this technique have shown encouraging results; however, the safety and tolerability of this method of brain stimulation have not been sufficiently explored yet. The purpose of our study was to assess the effects of direct current (DC) and alternating current (AC) stimulation at different intensities in order to measure their effects on cognition, mood, and electroencephalogram. Methods: Eighty-two healthy, right-handed subjects received active and sham stimulation in a randomized order. We conducted 164 ninety-minute sessions of electrical stimulation in 4 different protocols to assess safety of (1) anodal DC of the dorsolateral prefrontal cortex (DLPFC); (2) cathodal DC of the DLPFC; (3) intermittent anodal DC of the DLPFC and; (4) AC on the zygomatic process. We used weak currents of 1 to 2 mA (for DC experiments) or 0.1 to 0.2 mA (for AC experiment). Results: We found no significant changes in electroencephalogram, cognition, mood, and pain between groups and a low prevalence of mild adverse effects (0.11% and 0.08% in the active and sham stimulation groups, respectively), mainly, sleepiness and mild headache that were equally distributed between groups. Conclusions: Here, we show no neurophysiological or behavioral signs that transcranial DC stimulation or AC stimulation with weak currents induce deleterious changes when comparing active and sham groups. This study provides therefore additional information for researchers and ethics committees, adding important results to the safety pool of studies assessing the effects of cortical stimulation using weak electrical currents. Further studies in patients with neuropsychiatric disorders are warranted.
A least-voltage drop high output resistance current source for neural stimulation
2010
This paper presents a feedback technique to increase the output resistance of a MOS current mirror circuit that requires only one effective drain-source voltage drop. The proposed circuit requires a few additional current braches to form two feedback loops. With its compact structure, the proposed circuit is suitable as a current generator for neural stimulation. Simulation results, using 0.35 μm AMIS I3T25 technology, show that the proposed current generator, applied for bi-phasic stimulation, can convey more charge to a series resistive-capacitive load compared to the widely use low-voltage cascode current source.
The Rationale Driving the Evolution of Deep Brain Stimulation to Constant-Current Devices
Neuromodulation: Technology at the Neural Interface, 2014
Objective: Deep brain stimulation (DBS) is an effective therapy for the treatment of a number of movement and neuropsychiatric disorders. The effectiveness of DBS is dependent on the density and location of stimulation in a given brain area. Adjustments are made to optimize clinical benefits and minimize side effects. Until recently, clinicians would adjust DBS settings using a voltage mode, where the delivered voltage remained constant. More recently, a constant-current mode has become available where the programmer sets the current and the stimulator automatically adjusts the voltage as impedance changes. Methods: We held an expert consensus meeting to evaluate the current state of the literature and field on constant-current mode versus voltage mode in clinical brain-related applications. Results/Conclusions: There has been little reporting of the use of constant-current DBS devices in movement and neuropsychiatric disorders. However, as impedance varies considerably between patients and over time, it makes sense that all new devices will likely use constant current.
Selective electrical stimulation with currentfield modulation
Current Directions in Biomedical Engineering
Selective electrical stimulation using a multielectrode array is a promising technique that can potentially bring electrical stimulation treatment modalities a step forward. A microcontroller-controlled electrical stimulator system delivering a single pulse was designed, suitable for current-field modulation. The goal is to make electrical stimulation with surface electrodes more specific. A graphical user interface (GUI) was developed to control stimulation parameters and current-field within a multi-electrode array wirelessly. The stimulator generates arbitrary biphasic waveforms with a 5-bit resolution and high temporal precision (<10 μs) and was demonstrated to stimulate posterior lumbar root fibers in transcutaneous spinal cord stimulation (tSCS) treatment selectively. Current-field modulation throughout a sixteen-electrode array was achieved. The system has the goal to improve control of stimulation conditions in electrophysiological studies and time-dependent and site-spec...