Cochlear Implant Envelope Derivative Stimulation
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Solution Overview
Problem
Existing cochlear implant stimulation strategies, such as CIS and FSP, are imperfect due to non-specificity to signal properties, high power consumption, and channel interactions, with pulse rates not accurately reflecting auditory nerve physiology.
Innovation Solution
A signal processing approach that generates electrode stimulation signals by extracting information from the rate of change of signal envelopes, using derivatives to define stimulation timings and amplitudes, and incorporating physiological properties of auditory nerve tissue, such as First Spike Latency, to adapt stimulus delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If constant rate stimulation pulses are applied across all electrodes, then device operation is simplified, but temporal representation of envelope signal is insufficient
Solution Approach 1:
The patent implements dynamic pulse rates that adapt to the temporal characteristics of the envelope signal. Different electrodes receive stimulation pulses at different rates based on their specific frequency bands and the temporal modulation of the input signal, rather than using a uniform constant rate across all channels. This dynamic approach maintains temporal fidelity while remaining computationally feasible.
Solution Approach 2:
The system changes the stimulation rate parameter dynamically based on the envelope signal characteristics. By adjusting the pulse rate according to the temporal modulation frequency of each channel's envelope, the system optimizes temporal representation without requiring overly complex processing.
2Manufacturing precision
If high overall stimulation rate is used, then temporal representation is improved, but power consumption increases
Solution Approach 1:
The patent applies different stimulation rates to different electrodes based on their specific needs. Channels with high temporal modulation content receive higher pulse rates, while channels with slower modulation receive lower rates. This localized optimization reduces overall power consumption while maintaining temporal representation where it is most critical.
Solution Approach 2:
The system applies high stimulation rates only partially - specifically to those channels and time periods where temporal representation is most important. Rather than uniformly high rates across all channels, the system selectively increases rates only where the envelope signal requires fine temporal resolution, reducing unnecessary power consumption.
3Device complexity
If envelope detection is used for all channels, then processing is simplified, but fine time structure information is lost
Solution Approach 1:
The patent segments the signal processing approach by channel, applying different processing strategies to different frequency bands. Low-frequency channels preserve fine time structure information while high-frequency channels use envelope detection. This segmented approach maintains information where it matters most while keeping overall processing complexity manageable.
Solution Approach 2:
The system changes the processing parameter (envelope detection vs. fine structure preservation) based on the frequency band being processed. By adapting the processing approach to the temporal characteristics of each frequency range, the system preserves fine time structure information in appropriate channels without requiring complex processing across all channels.
4Measurement precision
If more electrodes are used with narrower frequency bands, then frequency resolution is improved, but channel interactions increase
Solution Approach 1:
The patent applies preliminary signal processing and filtering to minimize channel interactions before stimulation. By pre-processing the signal to reduce spectral leakage and cross-channel contamination, the system can use more electrodes with narrower bands without exacerbating interaction problems. The filtering and envelope detection processes prepare the signal in advance to prevent interactions.
Data Source
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AI summary
An implantable stimulation arrangement is described for generating electrode stimulation signals for an implanted electrode array having stimulation electrodes. A filter bank pre-processor processes an input acoustic audio signal to generate band pass signals each corresponding to an associated band of audio frequencies. A signal envelope module computes a corresponding signal envelope for each band pass signal. A stimulation pulse generator extracts stimulation signal information from the rate of change of the signal envelopes such as a time-based derivative to generate stimulation event signals defining electrode stimulation timings and amplitudes for some or all of the stimulation electrodes.