David Liebetanz

Georg-August-Universität Göttingen, Göttingen, Lower Saxony, Germany

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Publications (87)277.22 Total impact

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    ABSTRACT: Purpose: Providing mobility solutions for individuals with tetraplegia remains challenging. Existing control devices have shortcomings such as varying or poor signal quality or interference with communication. To overcome these limitations, we present a novel myoelectric auricular control system (ACS) based on bilateral activation of the posterior auricular muscles (PAMs). Methods: Ten able-bodied subjects and two individuals with tetraplegia practiced PAM activation over 4 days using visual feedback and software-based training for 1 h/day. Initially, half of these subjects were not able to voluntarily activate their PAMs. This ability was tested with regard to 8 parameters such as contraction rate, lateralized activation, wheelchair speed and path length in a virtual obstacle course. In session 5, all subjects steered an electric wheelchair with the ACS. Results: Performance of all subjects in controlling their PAMs improved steadily over the training period. By day 5, all subjects successfully generated basic steering commands using the ACS in a powered wheelchair, and subjects with tetraplegia completed a complex real-world obstacle course. This study demonstrates that the ability to activate PAM on both sides together or unilaterally can be learned and used intuitively to steer a wheelchair. Conclusions: With the ACS we can exploit the untapped potential of the PAMs by assigning them a new, complex function. The inherent advantages of the ACS, such as not interfering with oral communication, robustness, stability over time and proportional and continuous signal generation, meet the specific needs of wheelchair users and render it a realistic alternative to currently available assistive technologies.
    11/2015; DOI:10.3233/RNN-150579
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    ABSTRACT: Transcranial electrical stimulation (tES), including transcranial direct and alternating current stimulation (tDCS, tACS) are non-invasive brain stimulation techniques increasingly used for modulation of central nervous system excitability in humans. Here we address methodological issues required for tES application. This review covers technical aspects of tES, as well as applications like exploration of brain physiology, modelling approaches, tES in cognitive neurosciences, and interventional approaches. It aims to help the reader to appropriately design and conduct studies involving these brain stimulation techniques, understand limitations and avoid shortcomings, which might hamper the scientific rigor and potential applications in the clinical domain.
    Clinical Neurophysiology 11/2015; DOI:10.1016/j.clinph.2015.11.012 · 3.10 Impact Factor
  • Jonna Meincke · Manuel Hewitt · Giorgi Batsikadze · David Liebetanz ·
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    ABSTRACT: Background: Although neuronavigation is increasingly used for optimizing coil positioning, the inter-session reliability of hotspot location remains unsatisfactory, probably due to the variability of motor evoked potentials (MEPs) and residual investigator bias. Purpose: To increase the reliability and accuracy of hotspot location we introduce a novel automated hotspot-hunting procedure (AHH). Methods: AHH is based on resting motor thresholds (RMTs) instead of MEP amplitudes. By combining robotic coil positioning with a closed loop target search algorithm AHH runs independently from the investigator. AHH first identifies all targets with an RMT below a defined intensity of stimulator output (MEP-positive) and then locates the motor hotspot of a target muscle by measuring RMTs at all identified MEP-positive targets. Results were compared to robotic MEP amplitude TMS mapping (MAM) using a 7×7 predefined target grid and suprathreshold intensities and manual hotspot search (MHS). Sequence of stimulation was randomized from pulse to pulse in AHH and MAM. Each procedure was tested in 8 subjects. Results: Inter-session CoG shift was significantly reduced with AHH (1.4mm (SEM: 0.4)) as compared to MAM (7.0mm (SEM: 1.8)) (p=0.018) and MHS (9.6mm (SEM: 2.2)) (p=0.007). No statistical difference was observed between MAM and MHS. RMTs were reliable between sessions. Conclusion: Our method represents the first fully automated, i.e. investigator-independent, TMS hotspot-hunting procedure. Measuring RMTs instead of MEP amplitudes leads to significantly increased accuracy and reliability of CoG locations. Moreover, by assessing thresholds AHH is the first procedure to fulfill the original hotspot definition.
    NeuroImage 09/2015; 124(Pt A). DOI:10.1016/j.neuroimage.2015.09.013 · 6.36 Impact Factor
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    ABSTRACT: Bioelectric signals are often used for control purposes in rehabilitation engineering. As an example, the antagonistic myoelectric control is the de-facto standard for the control of hand prostheses. Lately, examinations have started to control wheelchairs via the EMG of two earmuscles. Typically, the generated signals show individual amplitudes and unintended coactivations hindering a direct interpretation of the user intention. This article discusses effects and influencing factors affecting the quality of the myoelectric signal and provides a signal processing pipeline to improve the estimation of the user intention. Standardized training paradigms are introduced to individually adapt parameters. Regression models help in minimizing the effects of co-activations. The functionality of the approach is shown using simulated and real-world data of two-channel EMG-measurements of forearm and ear. Bioelektrische Signale werden oft für Steuerungsaufgaben in der Rehabilitationstechnik eingesetzt. So stellt die antagonistische myoelektrische Steuerung den de-facto Standard für die Ansteuerung von Handprothesen dar. Neuerdings wird auch die Navigation eines Elektrorollstuhls über die Kontraktionen zweier Ohrmuskeln erforscht. Charakteristisch für diese Anwendungen sind individuelle Amplituden und unbeabsichtigte Koaktivierungen, die eine direkte Interpretation der Intention des Anwenders erschweren. Dieser Artikel diskutiert Einflussgrößen auf die Qualität der myoelektrischen Signale und stellt eine Signalverarbeitungskette zur Bereinigung des Signals bzw. zur Intentionsschätzung vor. Zur individuellen Anpassung der Parameter werden standardisierte Trainingsparadigmen eingeführt. Mit Hilfe von Regressionsmodellen sollen Fehlerquellen wie Koaktivierungen eliminiert werden. Die Funktionalität der Verfahren wird anhand simulierter und realer Daten von zweikanaligen myoelektrischen Messungen von Unterarm und Ohr nachgewiesen.
    tm - Technisches Messen 09/2015; 82(9):411-421. DOI:10.1515/teme-2015-0023 · 0.12 Impact Factor
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    ABSTRACT: Duchenne muscular dystrophy (DMD) is a severe hereditary myopathy. Standard treatment by glucocorticosteroids is limited due to numerous side effects. The aim of this study was to test immunomodulation by immunoglobulin G (IgG) as treatment in the experimental mouse model (mdx) of DMD. 2g/kg human IgG compared to human albumin was injected intraperitoneally in mdx mice at the age of 3 and 7 weeks. Advanced voluntary wheel running parameters were recorded continuously. After 8 weeks, animals were sacrificed so that blood, diaphragm and lower limb muscles could be removed for quantitative PCR, histological analysis and ex vivo muscle contraction tests. IgG compared to albumin significantly improved the voluntary running performance and reduced muscle fatigability in an ex vivo muscle contraction test. Upon IgG treatment, serum creatine kinase values were diminished and mRNA expression levels of relevant inflammatory markers were reduced in the diaphragm and limb muscles. Macrophage infiltration and myopathic damage were significantly ameliorated in the quadriceps muscle. Collectively, this study demonstrates that, in the early disease course of mdx mice, human IgG improves the running performance and diminishes myopathic damage and inflammation in the muscle. Therefore, IgG may be a promising approach for treatment of DMD. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 07/2015; DOI:10.1111/jnc.13269 · 4.28 Impact Factor
  • F. Klinker · D. Liebetanz ·
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    ABSTRACT: In addition to genetic factors, several secondary causes of restless legs syndrome (RLS) are known. Nevertheless, the exact pathomechanism eliciting RLS symptoms remains elusive, supporting the need for an animal model of RLS. As one genetically determined factor, reduced dopamine D3 receptor (D3R) function has been proposed. Iron deficiency is the most widely accepted secondary factor for the development of RLS. Mice lacking the D3R and made iron deficient exhibit increased locomotion before the resting period and enhanced responses to both acute and persistent pain stimuli. The behavioral changes observed in these animals are commensurate with what one would expect as the RLS phenotype in mice and underline the value of the combined D3R and iron-deficient mouse model of RLS. The assessment of therapeutic effects and the characterization of sleep changes in this model could further prove the validity of the presented model.
    Movement Disorders, 01/2015: pages 1163-1169; , ISBN: 9780124051959

  • Clinical & Experimental Immunology 12/2014; 178 Suppl 1(S1):132-3. DOI:10.1111/cei.12541 · 3.04 Impact Factor
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    ABSTRACT: As the determination of suitable and individualized parameter values for myoelectric-controlled human-machine interfaces is time-consuming, this work presents an incremental parameter adaptation scheme that finds appropriate parameter values autonomously. It incrementally adapts the values depending upon the user performance which is evaluated during task run time. The scheme is capable to cope with inappropriately initialized parameter values. In experiments it is validated for two scenarios simulating inappropriate parameter values.
    Biomedizinische Technik/Biomedical Engineering 10/2014; 59(S1):S148-S151. · 1.46 Impact Factor

  • 19th International Congress of the World-Muscle-Society; 10/2014
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    ABSTRACT: The neuromodulator dopamine plays an important role in synaptic plasticity. The effects depend on receptor subtypes, affinity, concentration level, and the kind of neuroplasticity induced. In animal experiments, dopamine D2-like receptor stimulation revealed partially antagonistic effects on plasticity, which might be explained by dosage dependency. In humans, D2 receptor block abolishes plasticity, and the D2/D3, but predominantly D3, receptor agonist ropinirol has a dosage-dependent nonlinear affect on plasticity. Here we aimed to determine the specific affect of D2 receptor activation on neuroplasticity in humans, because physiological effects of D2 and D3 receptors might differ. Therefore, we combined application of the selective D2 receptor agonist bromocriptine (2.5, 10, and 20 mg or placebo medication) with anodal and cathodal transcranial direct current stimulation (tDCS), which induces nonfocal plasticity, and with paired associative stimulation (PAS) generating a more focal kind of plasticity in the motor cortex of healthy humans. Plasticity was monitored by transcranial magnetic stimulation-induced motor-evoked potential amplitudes. For facilitatory tDCS, bromocriptine prevented plasticity induction independent from drug dosage. However, its application resulted in an inverted U-shaped dose-response curve on inhibitory tDCS, excitability-diminishing PAS, and to a minor degree on excitability-enhancing PAS. These data support the assumption that modulation of D2-like receptor activity exerts a nonlinear dose-dependent effect on neuroplasticity in the human motor cortex that differs from predominantly D3 receptor activation and that the kind of plasticity-induction procedure is relevant for its specific impact.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 08/2014; 34(32):10701-9. DOI:10.1523/JNEUROSCI.0832-14.2014 · 6.34 Impact Factor
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    Proc., 23. Workshop Computational Intelligence; 12/2013
  • M. Hewitt · J. Meincke · R. Ahlert · H. Scherberger · D. Liebetanz ·

    Clinical Neurophysiology 10/2013; 124(10):e177-e178. DOI:10.1016/j.clinph.2013.04.310 · 3.10 Impact Factor
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    Biomedizinische Technik/Biomedical Engineering 09/2013; DOI:10.1515/bmt-2013-4388 · 1.46 Impact Factor
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    ABSTRACT: Objective: Transcranial direct current stimulation (tDCS) induces polarity-specific changes of cerebral blood flow (CBF). To determine whether these changes are focally limited or if they incorporate large cortical regions and thus have the potential for a therapeutic application, we investigated the effects of cathodal tDCS on CBF in an established tDCS rat model with particular attention to the spatial extension in CBF changes using laser Doppler blood perfusion imaging (LDI). Methods: Twenty-one Sprague Dawley rats received a single 15-minute session of cathodal tDCS at current intensities of 200, 400, 600, or 700 μA applied over electrode contact areas (ECA) of 3·5, 7·0, 10·5, or 14·0 mm(2). One animal died prior to the stimulation. Cerebral blood flow was measured prior and after tDCS with LDI in three defined regions of interest (ROI) over the stimulated left hemisphere (region anterior to ECA - ROI 1, ECA - ROI 2, region posterior to ECA - ROI 3). Results: A regional decrease in CBF was measured after cathodal tDCS, the extent of the decrease depending on the current density applied. The most effective and spatially limited reduction in CBF (up to 50%, lasting as long as 90 minutes) was found after the application of 600 μA over an ECA of 10·5 mm(2). This significant reduction in CBF even lasted up to 90 minutes in distant cortical areas (ROI 1 and 3) that were not directly related to the ECA (ROI 2). Discussion: Cathodal tDCS induces a regional, long-lasting, reversible decrease in CBF that is not limited to the region to which tDCS is applied.
    Neurological Research 07/2013; 35(10). DOI:10.1179/1743132813Y.0000000248 · 1.44 Impact Factor
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    ABSTRACT: Purpose: Functional electrical stimulation represents an alternative to conventional and passive ankle foot orthosis (AFO) for the treatment of stroke-related drop foot. We evaluated the implantable 4-channel stimulator ActiGait, which selectively and directly stimulates the peroneal nerve. In addition, it bypasses the need for surface electrodes and cables. Methods: Walking speed (10-meter gait test, [m/s]) and walking endurance (6-minute gait test [m/6min]) of 5 patients were tested prior to, as well as 6 and 12 weeks after, the implantation of the ActiGait implantable drop foot stimulator system. In addition, ankle joint angles were assessed during specific phases of the gait cycle, i.e. initiation angle (IA) at the first contact of the foot to the floor, initial plantar flexion (IPF), dorsiflexion (DF) and final plantar flexion (FPF) in [°] during stance phase. The ankle joint angles were measured at baseline and 12 weeks after ActiGait implantation. Results: At the first follow-up, patients' gait speed was found to have increased (0.55; 0.77 m/s) as had walking endurance (211; 260 m). Improvement in gait speed (0.55; 0.77 m/s) and endurance (214; 248 m) was still present after 12 weeks. In addition, gait analysis after 12 weeks revealed a nearly normal physiological initiation angle (113° vs 122°) and an increase in the initial plantar flexion (7° vs. 0°). The initiation angle (IA) represents a well-suited parameter for adequate pre-positioning of the foot at the beginning of the stance phase and is necessary to prevent stumbling and falling. Furthermore, IA is identical to the maximum achieved dorsiflexion during the swing phase of gait. Thus, analysis of the IA of subjects walking with the implantable drop foot stimulator systems ActiGait is particularly useful in showing that the implantable system restores the IA towards physiological ankle movements. Conclusion: The ActiGait system increased gait speed, walking endurance and the physiology of important ankle joint kinematics. This is most likely a result of ankle dorsiflexion by active peroneal stimulation during the swing phase of gait and optimized prepositioning (IA) of the foot at the beginning of stance phase. The ActiGait system represents a therapeutic option for the treatment of patients suffering drop foot due to a cerebrovascular insult.
    06/2013; 31(5). DOI:10.3233/RNN-120283
  • A. Kutschenko · M. C. Reinert · F. Klinker · W. Paulus · S. Hesse · D. Liebetanz ·

    Toxicon 06/2013; 68:90. DOI:10.1016/j.toxicon.2012.07.090 · 2.49 Impact Factor
  • A. Kutschenko · M. C. Reinert · F. Klinker · W. Paulus · S. Hesse · D. Liebetanz ·

    Toxicon 06/2013; 68:89–90. DOI:10.1016/j.toxicon.2012.07.089 · 2.49 Impact Factor
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    ABSTRACT: Dopaminergic signaling influences physical activity. Notably impaired D2 receptor (D2R) function has been associated with decreased voluntary physical activity. Most animal models investigating effects of genetic or pharmacological dopaminergic modulation measure physical activity for a limited time of up to few hours. The aim of this study is to investigate the impact of chronic or acute D2R dysfunction on physical activity over several days. For this purpose, we used a highly automated running wheel system to continuously record physical activity in mice. We found that D2R knockout status led to a permanent decrease of running wheel activity. In contrast, acute D2R blockade by raclopride (1,5-5mg/kg) resulted in an initial dose dependent reduction of running wheel usage and a compensating increase of activity in later stages of the activity phase. This indicates that D2R dysfunction reduces physical activity. Our data indicate that this reduction to a large extent cannot be explained by motor deficits. The delayed increase of activity after D2R blockade might be due to a rebound effect.
    Behavioural brain research 01/2013; 242(1). DOI:10.1016/j.bbr.2012.12.038 · 3.03 Impact Factor
  • Dirk Czesnik · David Liebetanz ·
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    ABSTRACT: We report on a 61-year-old woman with cupulolithiasis of the right horizontal semicircular canal, which is usually difficult to treat. The patient reported that several years ago, similar symptoms relieved completely after having performed several somersaults together with her granddaughter. This time, repetitive somersaults were again effective to treat her benign paroxysmal positional vertigo. Acceleration during a somersault may induce an intracanalicular force strong enough to detach otoconia debris from the cupula. Rolling may then promote their reentrance into the utricle. This case suggests that repetitive somersaults may be an alternative treatment of cupulolithiasis of the horizontal semicircular canal.
    American journal of otolaryngology 01/2013; 34(1):72–74. DOI:10.1016/j.amjoto.2012.07.002 · 0.98 Impact Factor
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Publication Stats

5k Citations
277.22 Total Impact Points


  • 2002-2014
    • Georg-August-Universität Göttingen
      • Department of Clinical Psychology and Psychotherapy
      Göttingen, Lower Saxony, Germany
  • 2011
    • Universitätsklinikum Freiburg
      • Department of Clinical Psychology and Psychophysiology
      Freiburg an der Elbe, Lower Saxony, Germany
  • 2009-2010
    • Universitätsmedizin Göttingen
      Göttingen, Lower Saxony, Germany