Current Waveforms for Neural Stimulation-Charge Delivery With Reduced Maximum Electrode Voltage

Abstract

This paper contains results on the design of electrical signals for delivering charge through electrodes to achieve neural stimulation while reducing the peak electrode voltage. A generalization of the usual constant current stimulation phase to a stepped current waveform is presented. Techniques based on optimization and linear dynamic system theory are then applied to design the magnitude of each current segment in such a way as to minimize the maximum electrode voltage, while transferring a designated quantity of charge in a specified time. Experimental results are provided which validate the approach in saline and in neural tissue.

Phosphene brightness modelling for voltage driven waveforms

“…The work herein hinges upon the methodology of [9]. We utilise a current-driven approximation to a voltage-driven stimulation.…”

“…If desired, voltage balance may be achieved by applying, for instance, −f v (t − T ). Using the method described in [9], we construct a current-driven waveform, f a (t), out of piecewiseconstant current levels which produce a voltage similar to f v (t). From the piecewise constant-current approximation, f a (t), phosphene brightness is considered in Section II-B.…”

“…This paper discusses the impact of voltage-driven stimulation on the safety of chronic stimulation and on the perceived brightness of phosphenes elicited. This is accomplished by first constructing a current-driven waveform that is approximation to a constant voltage-driven waveform following the procedure in [9]. With that approxmiation, we are able to utilise existing models for safety [7] and perceived phosphene brightness [5].…”

“…In Section II, we outline the voltage-driven waveform model based on [9], the current-based brightness model of [5], and provide means to combine the two. The safety criteria, brightness predictions and example calculations are provided in Section III.…”

A Fully Intraocular High-Density Self-Calibrating Epiretinal Prosthesis

“…Several studies have shown that more sophisticated waveforms such as high-frequency pulse trains, asymmetric biphasic pulses, or non-rectangular shapes (Gaussian, linear and exponential), present advantages over biphasic pulses [21]- [24]. A recent publication [25] has proved that flexible stimulation such as step-down current pulse shape can potentially reduce the required voltage compliance by 10%-15%. Thus, having a highly flexible stimulation waveform is desirable and allows further studies in stimulation efficiency, color perception and multi-channel stimulation [5], [24], [26].…”