Compound Action Potential Detection Using Basis Function Decomposition
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Solution Overview
Problem
The challenge of accurately detecting compound action potentials (CAPs) in neural recordings is exacerbated by the presence of stimulus artefact, which is particularly difficult in implantable devices due to their compact size and limited power budget, requiring amplifiers with impractical dynamic ranges to distinguish the much smaller CAP signals from the significant stimulus artefact.
Innovation Solution
A system and method using basis functions to decompose neural recordings into compound action potentials and artefacts, employing a processor to separate these components efficiently, allowing for real-time estimation and removal of artefacts while maintaining computational efficiency and power constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stimulus electrodes and recording electrodes are placed in close proximity to characterize dorsal column responses, then measurement sensitivity is improved, but stimulus artefact increases making CAP detection difficult
Solution Approach 1:
The patent segments the compound signal into distinct components (CAP and stimulus artefact) using basis function decomposition. The recorded signal is modeled as a linear combination of a CAP basis function and an artefact basis function, allowing separate estimation and isolation of each component despite their temporal overlap.
Solution Approach 2:
The patent introduces basis functions as intermediary mathematical models that represent the characteristic shapes of CAP and artefact signals. These basis functions serve as templates that facilitate the decomposition and separation of the mixed signal components through projection and optimization techniques.
2Measurement precision
If high stimulation currents are used to evoke detectable CAP responses, then signal amplitude is improved, but stimulus artefact magnitude increases
Solution Approach 1:
The patent replaces traditional hardware-based artefact reduction methods (such as complex amplifier designs with impractical dynamic ranges) with a software-based signal processing approach. By using basis function decomposition and mathematical modeling, the system achieves effective CAP extraction without requiring specialized hardware with extreme dynamic range capabilities.
3Measurement precision
If an amplifier with high dynamic range is used to resolve CAP signals from artefact, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent substitutes complex hardware amplifier design with a computational signal processing approach. Instead of relying on an amplifier with 134 dB dynamic range to resolve 10 μV CAP signals from 5 V stimulus artefact, the system uses basis function decomposition that can separate these components through mathematical modeling, significantly reducing hardware complexity and power requirements.
Solution Approach 2:
The patent changes the approach from hardware parameter optimization (amplifier dynamic range) to software parameter optimization (basis function selection and decomposition parameters). By adjusting mathematical parameters rather than hardware specifications, the system achieves the same measurement precision with much lower device complexity and power consumption.
4Reliability
If regular CAP detection is implemented in implanted devices, then therapeutic monitoring is improved, but power budget is exceeded
Solution Approach 1:
The patent replaces power-intensive hardware-based CAP detection with a computationally efficient software-based approach. The basis function decomposition method requires fewer processor instructions compared to traditional methods, enabling regular CAP detection in implanted devices without exceeding the limited power budget while maintaining reliable therapeutic monitoring.
Solution Approach 2:
The patent applies a simplified yet effective version of signal decomposition that provides sufficient CAP detection capability without implementing the full complexity of traditional methods. By using predetermined basis functions and efficient projection algorithms, the system achieves adequate monitoring performance with reduced computational overhead and power consumption.
Data Source
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AI summary
Separating a compound action potential from an artefact in a neural recording. A memory stores a set of basis functions comprising at least one compound action potential basis function and at least one artefact basis function. A neural recording of electrical activity in neural tissue is decomposed by determining at least one of a compound action potential and an artefact from the set of basis functions. An estimate is output of at least one of a compound action potential and an artefact.