Neural Prosthesis Electrode Array Impedance Fitting

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Solution Overview

Problem

Current retinal prosthetic devices face challenges in adjusting individual electrode stimulation levels for optimal visual perception, as each person's response varies significantly, and manual adjustment is tedious and impractical, especially with high resolution electrode arrays, leading to potential retinal damage from excessive current use.

Innovation Solution

An automated method using impedance measurement to predict electrode height and threshold of perception, allowing for quick identification of defective electrodes and proper placement, which correlates with retinal thickness and stimulation thresholds, enabling efficient and safe neural stimulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If manual adjustment of electrode stimulation levels is performed, then individualized fitting can be achieved, but the process becomes tedious and impractical especially with high resolution electrode arrays

Engineering Contradiction:

Improveautomated electrode fittingVSAvoidstimulation threshold accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The patent replaces manual mechanical adjustment of electrode stimulation levels with an automated impedance measurement system. The system uses electrical impedance measurements to predict stimulation thresholds, eliminating the need for tedious manual adjustment while maintaining individualized fitting accuracy through the correlation between impedance and threshold values.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent enables the electrode array to self-characterize by measuring its own impedance properties. The system automatically determines stimulation thresholds through impedance measurements without requiring external manual calibration, allowing the device to perform its own fitting process efficiently.

Inventive Principle:

Principle #25Self-service

2Illumination intensity

If high current is used for neural stimulation, then adequate visual perception can be achieved, but retinal damage may occur

Engineering Contradiction:

Improvevisual perception intensityVSAvoidretinal damage risk

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary impedance measurements to predict stimulation thresholds before applying actual stimulation currents. By knowing the predicted thresholds in advance, the system can apply appropriate stimulation levels that achieve adequate visual perception while avoiding excessive currents that could cause retinal damage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses impedance measurements as feedback to adjust and optimize stimulation levels. The system continuously monitors impedance to predict thresholds and adjusts stimulation currents accordingly, ensuring adequate visual perception while preventing retinal damage through real-time parameter optimization.

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If electrode array is placed farther from retinal surface, then mechanical stability is improved, but stimulation efficiency decreases

Engineering Contradiction:

Improveelectrode mechanical stabilityVSAvoidstimulation current efficiency

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

The patent uses impedance measurements to detect and quantify changes in electrode-retinal distance. By monitoring impedance variations, the system can identify when electrodes have moved or detached, allowing for adjustment of stimulation parameters to compensate for distance changes and maintain stimulation efficiency while preserving mechanical stability.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces the variability in stimulation thresholds, maintains electrode proximity to the retinal surface, and decreases the risk of retinal damage, achieving stable and effective neural stimulation comparable to in vitro studies, with potential for higher resolution and longer-term use.

Implementation Method 1

Measure of impedance may be used to predict the electrode height from the neural tissue and, thereby, predict the threshold of perception

Methodology Applied

Scientific EffectImpedance measurement: Electrical Resistance

Data Source

PatentUS8190267B2Fitting a neural prosthesis using impedance and electrode height

Publication Date: 2012.05.29 CORTIGENT INC

AI summary

The invention is a method of automatically adjusting an electrode array to the neural characteristics of an individual subject. The response to electrical neural stimulation varies from subject to subject. Measure of impedance may be used to predict the electrode height from the neural tissue and, thereby, predict the threshold of perception. Alternatively, electrode height may be measured directly to predict the threshold of perception. Also, impedance measurement may be used to quickly identify defective electrodes and proper electrode placement.