Classification complexity in myoelectric pattern recognition.

Background: Limb prosthetics, exoskeletons, and neurorehabilitation devices can be intuitively controlled using myoelectric pattern recognition (MPR) to decode the subject's intended movement. In conventional MPR, descriptive electromyography (EMG) features representing the intended movement are fed...

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Published in:Journal of NeuroEngineering & Rehabilitation (JNER) Vol. 14; no. 1; pp. 1 - 19
Main Authors: Nilsson, Niclas, Håkansson, Bo, Ortiz-Catalan, Max
Format: research Journal Article
Published: BioMed Central 7/10/2017
Online Access:View this record in EBSCOhost
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      dt: 7/10/2017
      vid: 14
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      pid: 24147
      pub: BioMed Central
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        124073934
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        124073934
        10.1186/s12984-017-0283-5
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        124073934
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      tig:
        atl: Classification complexity in myoelectric pattern recognition.
      aug:
        au:
          Nilsson, Niclas
          Håkansson, Bo
          Ortiz-Catalan, Max
        affil: Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
      sug:
        subj:
          Information Science Methods
          Brain-Computer Interfaces
          Electromyography Classification
          Research Subjects
          Neural Networks (Computer)
          Electromyography Methods
          Signal Processing, Computer Assisted
          Grip Strength Physiology
          Prosthesis Design
          Volition
          Algorithms
          Movement
          Reproducibility of Results
          Discriminant Analysis
          Human
      ab: Background: Limb prosthetics, exoskeletons, and neurorehabilitation devices can be intuitively controlled using myoelectric pattern recognition (MPR) to decode the subject's intended movement. In conventional MPR, descriptive electromyography (EMG) features representing the intended movement are fed into a classification algorithm. The separability of the different movements in the feature space significantly affects the classification complexity. Classification complexity estimating algorithms (CCEAs) were studied in this work in order to improve feature selection, predict MPR performance, and inform on faulty data acquisition.Methods: CCEAs such as nearest neighbor separability (NNS), purity, repeatability index (RI), and separability index (SI) were evaluated based on their correlation with classification accuracy, as well as on their suitability to produce highly performing EMG feature sets. SI was evaluated using Mahalanobis distance, Bhattacharyya distance, Hellinger distance, Kullback-Leibler divergence, and a modified version of Mahalanobis distance. Three commonly used classifiers in MPR were used to compute classification accuracy (linear discriminant analysis (LDA), multi-layer perceptron (MLP), and support vector machine (SVM)). The algorithms and analytic graphical user interfaces produced in this work are freely available in BioPatRec.Results: NNS and SI were found to be highly correlated with classification accuracy (correlations up to 0.98 for both algorithms) and capable of yielding highly descriptive feature sets. Additionally, the experiments revealed how the level of correlation between the inputs of the classifiers influences classification accuracy, and emphasizes the classifiers' sensitivity to such redundancy.Conclusions: This study deepens the understanding of the classification complexity in prediction of motor volition based on myoelectric information. It also provides researchers with tools to analyze myoelectric recordings in order to improve classification performance.
      pubtype: Academic Journal
      doctype:
        research
        Journal Article
      ougenre: Article
    language: English
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