Cochlear Implant Discrete Stimulation via Interference
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Solution Overview
Problem
Conventional cochlear implants face limitations due to current spread, leading to undesirable effects such as distributed pitch perception, unpredictable loudness fluctuations, and loss of spectral shape, which are exacerbated by channel interaction when multiple electrodes are activated simultaneously.
Innovation Solution
A cochlear implant system that uses stimulating and limiting signals, determined by recipient-specific transimpedance measurements, to create discrete stimulation regions through constructive and destructive interference of signals applied to electrode channels, thereby minimizing current spread and channel interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current is delivered through a single electrode to stimulate a specific nerve region, then the intended nerve fibers are activated, but current spread causes stimulation of distant nerve regions leading to distributed pitch perception
Solution Approach 1:
The system segments the current delivery function by using multiple electrodes working in coordinated groups (triples) rather than a single electrode. Each triple consists of a stimulating electrode and two canceling electrodes that work together to confine current to a specific spatial region, thereby preventing current spread to distant nerve regions while maintaining precise spatial stimulation.
Solution Approach 2:
The system applies preliminary anti-action by using canceling electrodes that deliver currents specifically designed to counteract and nullify the spread of stimulating current before it can reach distant nerve regions. The canceling currents are pre-calculated based on transimpedance measurements to produce destructive interference with the spreading current, thereby preventing distributed pitch perception.
2Loss of information
If multiple electrodes are activated concurrently to represent sounds with multiple frequency components, then spectral information is conveyed, but channel interaction causes unpredictable loudness fluctuations and smearing of spatial representation
Solution Approach 1:
The system performs preliminary action by pre-calculating transimpedance matrices and determining optimal current configurations for each electrode triple before simultaneous stimulation. This pre-characterization of current spread patterns allows the system to predict and compensate for channel interactions, enabling multiple electrodes to be activated concurrently without causing loudness fluctuations or spectral smearing.
Solution Approach 2:
The system applies parameter changes by dynamically adjusting current amplitudes and polarities across multiple electrodes based on transimpedance measurements. By varying these electrical parameters according to pre-calculated configurations, the system maintains stable loudness perception and sharp spectral representation even when multiple channels are activated simultaneously.
3Object-generated harmful factors
If sequential pulsatile stimulation is used to circumvent channel interaction, then channel interaction is reduced, but temporal resolution and natural sound representation are compromised
Solution Approach 1:
The system segments the electrode activation pattern into spatially confined triples rather than activating all electrodes sequentially. This spatial segmentation allows simultaneous activation of multiple triples at different cochlear locations without significant channel interaction, thereby restoring temporal resolution and enabling natural sound representation with fine temporal structure.
Solution Approach 2:
The system converts the potentially harmful effect of current spread into a benefit by using it to define the stimulation region, then applying canceling currents only at the boundaries. This approach transforms the natural current spread phenomenon into a useful tool for defining excitation zones while eliminating the harmful lateral spread to adjacent channels, enabling both simultaneous multi-channel stimulation and precise temporal control.
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 allows for precise stimulation of discrete nerve regions, improving sound representation, speech understanding, and recognition of musical information by customizing the current balance across electrodes to negate current spread, resulting in more focused and controlled nerve excitation.
Implementation Method 1
The processing channels of the sound processor; that is, specific frequency bands with their associated signal processing paths, are mapped to a set of one or more electrodes to stimulate a desired nerve fiber or nerve region of the cochlear
Implementation Method 2
stimulation of a discrete stimulation region of a particular recipient's cochlear, said discrete stimulation region being defined by interference of stimulating and limiting signals simultaneously applied to electrode channels
Data Source
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AI summary
A medical stimulation device such as a cochlear implant configured to provide stimulation of one or more spatially-restricted contiguous portion(s) of the spiral array of auditory nerve fibers in the cochlear ("discrete stimulation regions"). Each discrete stimulation region is defined by the constructive and/or destructive interference of stimulating and limiting signals simultaneously applied to electrode channels of an implanted electrode array, the stimulating and limiting signals being determined based upon transimpedaπce measurements of intracochlear electrode channels of the implanted electrode array representing specific spread functions of an individual recipient. The stimulating signal is preferably applied through a targeted electrode channel; that is, one or more successive electrodes which is/are adjacent to the discrete stimulation region. The targeted electrode channel is selected to represent sound based on the outputs of a sound processor to stimulate neural activity in the discrete stimulation region to thereby cause a percept of the represented sound.