Electrical stimulation of excitable tissue: design of efficacious and safe protocols

Merrill, Daniel R.; Bikson, Marom; Jefferys, John G. R.

doi:10.1016/j.jneumeth.2004.10.020

Cited by 1,787 publications

(1,745 citation statements)

References 127 publications

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“…The specific capacitance reported here (c s ϳ3 F/cm 2 ) is similar to values obtained for high-kappa metal insulator-metal capacitors in electronic devices (Cheng et al 2008;Lin et al 2009). It exceeds the value reported for TiO 2 on silicon substrate (Wallrapp and Fromherz 2006) but is smaller than the Helmholtz capacitance (10 -20 F/cm 2 ) surrounding metallic stimulation electrodes immersed in electrolyte (Merrill et al 2005). Safe stimulation without faradaic current was limited here to 1.3 V. This limits the amount of stimulation current (Fig.…”

Section: Discussionmentioning

confidence: 54%

“…For technological reasons the entire CMOS chip is insulated by a thin and chemically inert oxide layer (TiO 2 /ZrO 2 ). The insulation prevents faradaic processes that may damage the interfaced neural tissue (reviewed in Merrill et al 2005) or may lead to electrode deterioration (Cogan 2008;Merrill et al 2005). On the other hand, the insulation lowers the specific electrode capacitance compared with metal electrodes; as a consequence the maximum capacitive stimulation current is lowered.…”

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confidence: 99%

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Electrical stimulation of retinal neurons in epiretinal and subretinal configuration using a multicapacitor array

Eickenscheidt

Jenkner

Thewes

et al. 2012

Journal of Neurophysiology

110

120

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Eickenscheidt M, Jenkner M, Thewes R, Fromherz P, Zeck G. Electrical stimulation of retinal neurons in epiretinal and subretinal configuration using a multicapacitor array. J Neurophysiol 107: 2742-2755, 2012. First published February 22, 2012 doi:10.1152/jn.00909.2011.-Electrical stimulation of retinal neurons offers the possibility of partial restoration of visual function. Challenges in neuroprosthetic applications are the long-term stability of the metal-based devices and the physiological activation of retinal circuitry. In this study, we demonstrate electrical stimulation of different classes of retinal neurons with a multicapacitor array. The array-insulated by an inert oxideallows for safe stimulation with monophasic anodal or cathodal current pulses of low amplitude. Ex vivo rabbit retinas were interfaced in either epiretinal or subretinal configuration to the multicapacitor array. The evoked activity was recorded from ganglion cells that respond to light increments by an extracellular tungsten electrode. First, a monophasic epiretinal cathodal or a subretinal anodal current pulse evokes a complex burst of action potentials in ganglion cells. The first action potential occurs within 1 ms and is attributed to direct stimulation. Within the next milliseconds additional spikes are evoked through bipolar cell or photoreceptor depolarization, as confirmed by pharmacological blockers. Second, monophasic epiretinal anodal or subretinal cathodal currents elicit spikes in ganglion cells by hyperpolarization of photoreceptor terminals. These stimuli mimic the photoreceptor response to light increments. Third, the stimulation symmetry between current polarities (anodal/cathodal) and retina-array configuration (epi/sub) is confirmed in an experiment in which stimuli presented at different positions reveal the center-surround organization of the ganglion cell. A simple biophysical model that relies on voltage changes of cell terminals in the transretinal electric field above the stimulation capacitor explains our results. This study provides a comprehensive guide for efficient stimulation of different retinal neuronal classes with low-amplitude capacitive currents.

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Section: Discussionmentioning

confidence: 54%

mentioning

confidence: 99%

Electrical stimulation of retinal neurons in epiretinal and subretinal configuration using a multicapacitor array

Eickenscheidt

Jenkner

Thewes

et al. 2012

Journal of Neurophysiology

110

120

View full text Add to dashboard Cite

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“…In turn, a more accurate representation of the tissue medium will undoubtedly introduce additional variability in the impedance. Further, we assume the electrode surface is perfectly smooth and ignore any electrode corrosion and surface modification that may occur as a result of prolonged stimulation (Merrill et al, 2005). Hence, the surface area specified in our electrode models represents an underestimate of the actual surface area of clinical electrodes.…”

Section: Discussionmentioning

confidence: 99%

Sources and effects of electrode impedance during deep brain stimulation

Butson

Maks

McIntyre

2006

Clinical Neurophysiology

320

281

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Objective-Clinical impedance measurements for deep brain stimulation (DBS) electrodes in human patients are normally in the range 500-1500 Ω. DBS devices utilize voltage-controlled stimulation; therefore, the current delivered to the tissue is inversely proportional to the impedance. The goals of this study were to evaluate the effects of various electrical properties of the tissue medium and electrode-tissue interface on the impedance and to determine the impact of clinically relevant impedance variability on the volume of tissue activated (VTA) during DBS.Methods-Axisymmetric finite-element models (FEM) of the DBS system were constructed with explicit representation of encapsulation layers around the electrode and implanted pulse generator. Impedance was calculated by dividing the stimulation voltage by the integrated current density along the active electrode contact. The models utilized a Fourier FEM solver that accounted for the capacitive components of the electrode-tissue interface during voltagecontrolled stimulation. The resulting time-and space-dependent voltage waveforms generated in the tissue medium were superimposed onto cable model axons to calculate the VTA.Results-The primary determinants of electrode impedance were the thickness and conductivity of the encapsulation layer around the electrode contact and the conductivity of the bulk tissue medium. The difference in the VTA between our low (790 Ω) and high (1244 Ω) impedance models with typical DBS settings (−3 V, 90 μs, 130 Hz pulse train) was 121 mm 3 , representing a 52% volume reduction.Conclusions-Electrode impedance has a substantial effect on the VTA and accurate representation of electrode impedance should be an explicit component of computational models of voltage-controlled DBS.Significance-Impedance is often used to identify broken leads (for values >2000 Ω) or short circuits in the hardware (for values <50 Ω); however, clinical impedance values also represent an important parameter in defining the spread of stimulation during DBS.

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“…A charge-imbalanced waveform injures tissue [17]. TMS, therefore, has the potential to injure neural tissue beyond the level predicted by studies of electrically induced tissue damage.…”

Section: Intensity Of Induced Current and Safety Limitmentioning

confidence: 99%

The safety of transcranial magnetic stimulation with deep brain stimulation instruments

Shimojima¹,

Morita

Nishikawa³

et al. 2010

Parkinsonism & Related Disorders

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Objectives: Transcranial magnetic stimulation (TMS) has been employed in patients with an implanted deep brain stimulation (DBS) device. We investigated the safety of TMS using simulation models with an implanted DBS device. Methods: The DBS lead was inserted into plastic phantoms filled with dilute gelatin showing impedance similar to that of human brain. TMS was performed with three different types of magnetic coil. During TMS (1) electrode movement, (2) temperature change around the lead, and (3) TMS-induced current in various situations were observed. The amplitude and area of each evoked current were measured to calculate charge density of the evoked current. Results: There was no movement or temperature increase during 0.2Hz repetitive TMS with 100% stimulus intensity for 1 hour. The size of evoked current linearly increased with TMS intensity. The maximum charge density exceeded the safety limit of 30C/cm 2 /phase during stimulation above the loops of the lead with intensity over 50% using a figure-eight coil. Conclusions:Strong TMS on the looped DBS leads should not be administered to avoid electrical tissue injury. Subcutaneous lead position should be pay enough attention for forthcoming situations during surgery.

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Electrical stimulation of excitable tissue: design of efficacious and safe protocols

Cited by 1,787 publications

References 127 publications

Electrical stimulation of retinal neurons in epiretinal and subretinal configuration using a multicapacitor array

Electrical stimulation of retinal neurons in epiretinal and subretinal configuration using a multicapacitor array

Sources and effects of electrode impedance during deep brain stimulation

The safety of transcranial magnetic stimulation with deep brain stimulation instruments

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