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Item type:Publication, Access status: with files , Long-term decoding of movement force and direction with a wireless myoelectric implant(IOP Publishing, 2015-12-08); ; ; ; 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. Approach. 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. Main 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. Significance. 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).Publicationtype: Journal ArticleScopus© Citations 23 338 405 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Development of a fully implantable EMG measurement system : status report on the MyoPlant project(De Gruyter, 2014); ; ; ; MyoPlant is a publicly funded research project that developed a fully implantable EMG measurement system. The system consists of a central implant, and single silicone electrodes that are placed on the muscles of choice. Electrodes are connected by means of subcutaneous cables. While electrodes were tested in rats, the complete system was tested in sheep and rhesus macaques. Electrodes showed good handling during surgery and were well tolerated by all animals without adverse reactions. No electrode defects were observed during the runtime of the project. Data from the animal trials showed that electrodes are well encapsulated after approximately eight weeks. The custom designed chip in the central implant performed as intended. Data transmission and inductive energy supply worked as designed. The latter was susceptible to coil misalignment. Electromyographic signals recorded with the system showed very good separation between electrodes, no cross-talk and no 50Hz noise. Amplitudes were consistent between sessions. Overall, we were able to demonstrate the technical feasibility of a fully implantable EMG measurement system. The recorded signals seem well suited to control modern myoelectric arm prostheses with multiple degrees of freedom in the future.Publicationtype: Journal Article58 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fully implantable multi-channel measurement system for acquisition of muscle activity(IEEE, 2013-05-07); ; ; ; This paper presents intramuscular electromyogram (EMG) signals obtained with a fully implantable measurement system that were recorded during goal directed arm movements. In a first implantation thin film electrodes were epimysially implanted on the deltoideus of a rhesus macaque and the encapsulation process was monitored by impedance measurements. Increase of impedance reached a constant level after four weeks indicating a complete encapsulation of electrodes. EMG recorded with these electrodes yielded a signal-to-noise ratio of about 80 dB at 200 Hz. The EMG recorded during goal-directed arm movements showed a high similarity to movements in the same direction and at the same time presented clear differences between different movement directions in time domain. Six classifiers and seven time and frequency domain features were investigated with the aim of discriminating the direction of arm movement from EMG signals. Reliable recognition of arm movements was achieved for a subset of the movements under investigation only. A second implantation of the whole measurement system for nine weeks demonstrated simple handling during surgery and good biotolerance in the animals.Publicationtype: Journal Article83 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Acquisition of muscle activity with a fully implantable multi-channel measurement systemThis work presents intramuscular measurements of the electromyogram (EMG) during goal directed arm movements. Thin film electrode arrays were epimysially implanted on the deltoideus of a rhesus macaque and the encapsulation process was monitored by impedance measurements. Increase of impedance plateaued after four weeks indicating a complete incorporation of electrodes. EMG recorded with these electrodes yielded a signal to noise ratio of about 80 dB at 200 Hz. The EMG recorded during goal directed arm movements showed high similarity amongst movements in the same direction while presenting clear differences between different movement directions. A second implantation of the whole measurement system for nine weeks proved good handling and biotolerance.Publicationtype: Conference Paper12