title: Long-term decoding of movement force and direction with a wireless myoelectric implant.
abstract: OBJECTIVE
  The ease of use and number of degrees of freedom of current myoelectric hand prostheses is limited by the information content and reliability of the surface electromyography (sEMG) signals used to control them. For example, cross-talk limits the capacity to pick up signals from small or deep muscles, such as the forearm muscles for distal arm amputations, or sites of targeted muscle reinnervation (TMR) for proximal amputations. Here we test if signals recorded from the fully implanted, induction-powered wireless Myoplant system allow long-term decoding of continuous as well as discrete movement parameters with better reliability than equivalent sEMG recordings. The Myoplant system uses a centralized implant to transmit broadband EMG activity from four distributed bipolar epimysial electrodes.
  
  
  METHODS
  Two Rhesus macaques received implants in their backs, while electrodes were placed in their upper arm. One of the monkeys was trained to do a cursor task via a haptic robot, allowing us to control the forces exerted by the animal during arm movements. The second animal was trained to perform a center-out reaching task on a touchscreen. We compared the implanted system with concurrent sEMG recordings by evaluating our ability to decode time-varying force in one animal and discrete reach directions in the other from multiple features extracted from the raw EMG signals.
  
  
  RESULTS
  In both cases, data from the implant allowed a decoder trained with data from a single day to maintain an accurate decoding performance during the following months, which was not the case for concurrent surface EMG recordings conducted simultaneously over the same muscles.
  
  
  CONCLUSIONS
  These results show that a fully implantable, centralized wireless EMG system is particularly suited for long-term stable decoding of dynamic movements in demanding applications such as advanced forelimb prosthetics in a wide range of configurations (distal amputations, TMR).
authors.affiliation: Cognitive Neuroscience Laboratory-Sensorimotor Group, German Primate Center-Leibniz Institute for Primate Research, Kellnerweg, 4, D-37077 Göttingen, Germany.
authors.forename: Pierre
authors.initials: P
authors.lastname: Morel
authors.forename: Enrico
authors.initials: E
authors.lastname: Ferrea
authors.forename: Bahareh
authors.initials: B
authors.lastname: Taghizadeh-Sarshouri
authors.forename: Josep Marcel Cardona
authors.initials: JM
authors.lastname: Audí
authors.forename: Roman
authors.initials: R
authors.lastname: Ruff
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Hoffmann
authors.forename: Sören
authors.initials: S
authors.lastname: Lewis
authors.forename: Michael
authors.initials: M
authors.lastname: Russold
authors.forename: Hans
authors.initials: H
authors.lastname: Dietl
authors.forename: Lait
authors.initials: L
authors.lastname: Abu-Saleh
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schroeder
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Krautschneider
authors.forename: Thomas
authors.initials: T
authors.lastname: Meiners
authors.forename: Alexander
authors.initials: A
authors.lastname: Gail
mesh_terms: D000669:Amplifiers, Electronic; D000818:Animals; D001132:Arm / Q000502:physiology; D004567:Electrodes, Implanted; D004576:Electromyography / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008137:Longitudinal Studies; D008251:Macaca; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D019736:Prostheses and Implants; D059015:Wireless Technology / Q000295:instrumentation*