title: Motor Unit Tracking Using High Density Surface Electromyography (HDsEMG) . Automated Correction of Electrode Displacement Errors.
abstract: BACKGROUND
  This article is part of the Focus Theme of Methods of Information in Medicine on "Biosignal Interpretation: Ad-vanced Methods for Neural Signals and Images".
  
  
  OBJECTIVE
  The study discusses a technique to automatically correct for effects of electrode grid displacement across serial surface EMG measurements with high-density electrode arrays (HDsEMG). The goal is to match motor unit signatures from subsequent measurements and by this, achieve automated motor unit tracking.
  
  
  METHODS
  Test recordings of voluntary muscle contractions using HDsEMG were performed on three healthy individuals. Electrode grid displacements were mimicked in repeated recordings while measuring the exact position of the grid. A concept of accounting for translational and rotational displacements by making the projection of the recorded motor unit action potentials is first introduced. Then, this concept was tested for the performed measurements attempting the automated matching of the similar motor unit action potentials across different trials.
  
  
  RESULTS
  The ability to perform automated correction (projection) of the isolated motor unit action potentials was first shown using large angular displacements. Then, for accidental (small) displacements of the recording grid, the ability to automatically track motor units across different measurement trials was shown. It was possible to track 10 -15% of identified motor units.
  
  
  CONCLUSIONS
  This proof of concept study demonstrates an automated correction allowing the identification of an increased number of same motor unit action potentials across different measurements. By this, great potential is demonstrated for assisting motor unit tracking studies, indicating that otherwise electrode displacements cannot always be precisely described.
authors.affiliation: Ivan Gligorijević, Ph.D., Faculty of Engineering Department of Electrical Engineering (ESAT), Division SCD/SISTA, KU Leuven, Kasteelpark Arenberg 10 postbus 2440, 3001 Heverlee, Belgium, E-mail: ivan@mbraintrain.com.
authors.forename: I
authors.initials: I
authors.lastname: Gligorijević
authors.forename: B T H M
authors.initials: BT
authors.lastname: Sleutjes
authors.forename: M
authors.initials: M
authors.lastname: De Vos
authors.forename: J H
authors.initials: JH
authors.lastname: Blok
authors.forename: I
authors.initials: I
authors.lastname: Montfoort
authors.forename: B
authors.initials: B
authors.lastname: Mijović
authors.forename: M
authors.initials: M
authors.lastname: Signoretto
authors.forename: S
authors.initials: S
authors.lastname: Van Huffel
mesh_terms: D000465:Algorithms; D004566:Electrodes; D004576:Electromyography / Q000379:methods* / Q000592:standards; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology
keywords: Grid displacement; HDsEMG; motor unit tracking; rotation; surface electromyography