Andreas Daffertshofer
Research interests
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InterestsComplex Systems
Publications
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2.41Impact points
Letter to the Editor: "Sensitivity of the Wolf's and Rosenstein's Algorithms to Evaluate Local Dynamic Stability from Small Gait Data Sets"
Annals of biomedical engineering. 05/2012;
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2.00Impact points
Removing ECG contamination from EMG recordings: A comparison of ICA-based and other filtering procedures.
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology. 01/2012;
Trunk muscle electromyography (EMG) is often contaminated by the electrocardiogram (ECG), which hampers data analysis and potentially yields misinterpretations. We propose the use of independent component analysis (ICA) for removing ECG contamination and compared it with other procedures previously ... [more] Trunk muscle electromyography (EMG) is often contaminated by the electrocardiogram (ECG), which hampers data analysis and potentially yields misinterpretations. We propose the use of independent component analysis (ICA) for removing ECG contamination and compared it with other procedures previously developed to decontaminate EMG. To mimic realistic contamination while having uncontaminated reference signals, we employed EMG recordings from peripheral muscles with different activation patterns and superimposed distinct ECG signals that were recorded during rest at conventional locations for trunk muscle EMG. ICA decomposition was performed with and without a separately collected ECG signal as part of the data set and contaminated ICA modes representing ECG were identified automatically. Root mean squared relative errors and correlations between the linear envelopes of uncontaminated and contaminated EMG were calculated to assess filtering effects on EMG amplitude. Changes in spectral content were quantified via mean power frequencies. ICA-based filtering largely preserved the EMG's spectral content. Performance on amplitude measures was especially successful when a separate ECG recording was included. That is, the ICA-based filtering can produce excellent results when EMG and ECG are indeed statistically independent and when mode selection is flexibly adjusted to the data set under study.
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On the Influence of Amplitude on the Connectivity between Phases.
Frontiers in neuroinformatics. 01/2011; 5:6.
In recent studies, functional connectivities have been reported to display characteristics of complex networks that have been suggested to concur with those of the underlying structural, i.e., anatomical, networks. Do functional networks always agree with structural ones? In all generality, this que... [more] In recent studies, functional connectivities have been reported to display characteristics of complex networks that have been suggested to concur with those of the underlying structural, i.e., anatomical, networks. Do functional networks always agree with structural ones? In all generality, this question can be answered with "no": for instance, a fully synchronized state would imply isotropic homogeneous functional connections irrespective of the "real" underlying structure. A proper inference of structure from function and vice versa requires more than a sole focus on phase synchronization. We show that functional connectivity critically depends on amplitude variations, which implies that, in general, phase patterns should be analyzed in conjunction with the corresponding amplitude. We discuss this issue by comparing the phase synchronization patterns of interconnected Wilson-Cowan models vis-à-vis Kuramoto networks of phase oscillators. For the interconnected Wilson-Cowan models we derive analytically how connectivity between phases explicitly depends on the generating oscillators' amplitudes. In consequence, the link between neurophysiological studies and computational models always requires the incorporation of the amplitude dynamics. Supplementing synchronization characteristics by amplitude patterns, as captured by, e.g., spectral power in M/EEG recordings, will certainly aid our understanding of the relation between structural and functional organizations in neural networks at large.
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3.12Impact points
Slowing of M1 activity in Parkinson's disease during rest and movement--an MEG study.
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 11/2010; 122(4):789-95.
Parkinson's disease is characterized by motor and cognitive problems that are accompanied by slowing of neural activity. This study examined the relationship between neural slowing and disease severity during rest and motor performance. Primary motor activity was assessed by means of magnetoence... [more] Parkinson's disease is characterized by motor and cognitive problems that are accompanied by slowing of neural activity. This study examined the relationship between neural slowing and disease severity during rest and motor performance. Primary motor activity was assessed by means of magnetoencephalography during rest and rhythmic movements. Motor output and event-related cortical power in the alpha and beta frequency bands were determined. UPDRS total and subscores were used to pinpoint correlates of neural slowing (change of power towards lower frequencies) during both resting state and the production of rhythmic movements. By design, motor performance was similar for both the patients and the controls. PD patients showed slowing of neural activity which increased with disease severity. Slowing during rest showed the clearest correlation with cognitive UPDRS subscores, whereas slowing during movement correlated best with the motor UPDRS subscore. These results suggest that slowing is functionally modulated and that different mechanisms are responsible for neural slowing during rest versus movement. Neural slowing must be viewed in a broader context than previously thought because it is not solely related to impaired motor performance but also to impaired cognition.
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5.74Impact points
Estimating complex cortical networks via surface recordings- a critical note.
NeuroImage. 11/2010; 53(2):439-49.
We discuss potential caveats when estimating topologies of 3D brain networks from surface recordings. It is virtually impossible to record activity from all single neurons in the brain and one has to rely on techniques that measure average activity at sparsely located (non-invasive) recording sites.... [more] We discuss potential caveats when estimating topologies of 3D brain networks from surface recordings. It is virtually impossible to record activity from all single neurons in the brain and one has to rely on techniques that measure average activity at sparsely located (non-invasive) recording sites. Effects of this spatial sampling in relation to structural network measures like centrality and assortativity were analyzed using multivariate classifiers. A simplified model of 3D brain connectivity incorporating both short- and long-range connections served for testing. To mimic M/EEG recordings we sampled this model via non-overlapping regions and weighted nodes and connections according to their proximity to the recording sites. We used various complex network models for reference and tried to classify sampled versions of the "brain-like" network as one of these archetypes. It was found that sampled networks may substantially deviate in topology from the respective original networks for small sample sizes. For experimental studies this may imply that surface recordings can yield network structures that might not agree with its generating 3D network.
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1.93Impact points
Stability and variability of acoustically specified coordination patterns while walking side-by-side on a treadmill: does the seagull effect hold?
Neuroscience letters. 03/2010; 474(2):79-83.
To examine whether the Haken-Kelso-Bunz model for rhythmic interlimb coordination applies to walking side-by-side on a treadmill, we invited six pairs of participants to coordinate their stepping movements at seven prescribed relative phases (between 0 degrees and 180 degrees ) to scan the attractor... [more] To examine whether the Haken-Kelso-Bunz model for rhythmic interlimb coordination applies to walking side-by-side on a treadmill, we invited six pairs of participants to coordinate their stepping movements at seven prescribed relative phases (between 0 degrees and 180 degrees ) to scan the attractor layout governing their coordination. Two auditory metronomes, one for each participant, specified the required relative phase. For each trial participants were instructed to synchronize their left heel strikes with the beeps of the metronome (2min) and to continue walking after the metronome stopped (1min). If the Haken-Kelso-Bunz model applies to interpersonal coordination during treadmill walking, then (1) the variability of in- and antiphase should be minimal, (2) intermediate relative phases should be attracted to either in- or antiphase, and (3) the absolute shift away from the required relative phase should be greatest for a required relative phase of 90 degrees . Only the third of these hypotheses was confirmed, indicating that the dynamical model for rhythmic interlimb coordination does not readily apply, at least not generically or robustly, to interpersonal coordination during walking side-by-side on a treadmill.
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6.98Impact points
Spectral changes of interhemispheric crosstalk during movement instabilities.
Cerebral cortex (New York, N.Y. : 1991). 02/2010; 20(11):2605-13.
Bimanual coordination requires the functional integration of the activity in various cortical, subcortical, spinal, and peripheral neural structures. We challenged this functional integration by destabilizing bimanual 5:8 tapping through an increase in movement tempo, while measuring brain and muscl... [more] Bimanual coordination requires the functional integration of the activity in various cortical, subcortical, spinal, and peripheral neural structures. We challenged this functional integration by destabilizing bimanual 5:8 tapping through an increase in movement tempo, while measuring brain and muscle activity using magnetoencephalography and electromyography. Movement instabilities were characterized by a drop in frequency locking. Time-frequency analysis revealed movement-related beta amplitude modulation in bilateral motor areas as well as movement-related corticospinal entrainment. Both of these synchronization patterns depended on movement tempo suggesting that the timescale needed for the upregulation and downregulation of beta synchrony in rhythmic tapping poses constraints on motor performance. Bilateral phase locking over movement cycles appeared to be mediated by beta-frequency oscillations and constrained by its phase dynamics. The timescale of beta synchrony thus seems to play a key role in achieving timed phase synchrony in the motor cortex and along the neural axis. Once event-related desynchronization-synchronization cycles cannot be build up properly, inhibition may become inadequate, resulting in a reduction of the stability of performance, which may eventually become unstable.
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2.30Impact points
Stochastic two-delay differential model of delayed visual feedback effects on postural dynamics.
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. 01/2010; 368(1911):423-38.
We report on experiments and modelling involving the 'visuo-postural control loop' in the upright stance. We experimentally manipulated an artificial delay to the visual feedback during standing, presented at delays ranging from 0 to 1 s in increments of 250 ms. Using stochastic delay differ... [more] We report on experiments and modelling involving the 'visuo-postural control loop' in the upright stance. We experimentally manipulated an artificial delay to the visual feedback during standing, presented at delays ranging from 0 to 1 s in increments of 250 ms. Using stochastic delay differential equations, we explicitly modelled the centre-of-pressure (COP) and centre-of-mass (COM) dynamics with two independent delay terms for vision and proprioception. A novel 'drifting fixed point' hypothesis was used to describe the fluctuations of the COM with the COP being modelled as a faster, corrective process of the COM. The model was in good agreement with the data in terms of probability density functions, power spectral densities, short- and long-term correlations (Hurst exponents) as well the critical time between the two ranges.
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4.41Impact points
Comparing brain networks of different size and connectivity density using graph theory.
PloS one. 01/2010; 5(10):e13701.
Graph theory is a valuable framework to study the organization of functional and anatomical connections in the brain. Its use for comparing network topologies, however, is not without difficulties. Graph measures may be influenced by the number of nodes (N) and the average degree (k) of the network.... [more] Graph theory is a valuable framework to study the organization of functional and anatomical connections in the brain. Its use for comparing network topologies, however, is not without difficulties. Graph measures may be influenced by the number of nodes (N) and the average degree (k) of the network. The explicit form of that influence depends on the type of network topology, which is usually unknown for experimental data. Direct comparisons of graph measures between empirical networks with different N and/or k can therefore yield spurious results. We list benefits and pitfalls of various approaches that intend to overcome these difficulties. We discuss the initial graph definition of unweighted graphs via fixed thresholds, average degrees or edge densities, and the use of weighted graphs. For instance, choosing a threshold to fix N and k does eliminate size and density effects but may lead to modifications of the network by enforcing (ignoring) non-significant (significant) connections. Opposed to fixing N and k, graph measures are often normalized via random surrogates but, in fact, this may even increase the sensitivity to differences in N and k for the commonly used clustering coefficient and small-world index. To avoid such a bias we tried to estimate the N,k-dependence for empirical networks, which can serve to correct for size effects, if successful. We also add a number of methods used in social sciences that build on statistics of local network structures including exponential random graph models and motif counting. We show that none of the here-investigated methods allows for a reliable and fully unbiased comparison, but some perform better than others.
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1.55Impact points
Generative models of cortical oscillations: neurobiological implications of the kuramoto model.
Frontiers in human neuroscience. 01/2010; 4:190.
Understanding the fundamental mechanisms governing fluctuating oscillations in large-scale cortical circuits is a crucial prelude to a proper knowledge of their role in both adaptive and pathological cortical processes. Neuroscience research in this area has much to gain from understanding the Kuram... [more] Understanding the fundamental mechanisms governing fluctuating oscillations in large-scale cortical circuits is a crucial prelude to a proper knowledge of their role in both adaptive and pathological cortical processes. Neuroscience research in this area has much to gain from understanding the Kuramoto model, a mathematical model that speaks to the very nature of coupled oscillating processes, and which has elucidated the core mechanisms of a range of biological and physical phenomena. In this paper, we provide a brief introduction to the Kuramoto model in its original, rather abstract, form and then focus on modifications that increase its neurobiological plausibility by incorporating topological properties of local cortical connectivity. The extended model elicits elaborate spatial patterns of synchronous oscillations that exhibit persistent dynamical instabilities reminiscent of cortical activity. We review how the Kuramoto model may be recast from an ordinary differential equation to a population level description using the nonlinear Fokker-Planck equation. We argue that such formulations are able to provide a mechanistic and unifying explanation of oscillatory phenomena in the human cortex, such as fluctuating beta oscillations, and their relationship to basic computational processes including multistability, criticality, and information capacity.
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2.11Impact points
Comparing unilateral and bilateral upper limb training: The ULTRA-stroke program design.
BMC neurology. 11/2009; 9(1):57.
ABSTRACT: BACKGROUND: About 80% of all stroke survivors have an upper limb paresis immediately after stroke, only about a third of whom (30 to 40%) regain some dexterity within six months following conventional treatment programs. Of late, however, two recently developed interventions - constraint-i... [more] ABSTRACT: BACKGROUND: About 80% of all stroke survivors have an upper limb paresis immediately after stroke, only about a third of whom (30 to 40%) regain some dexterity within six months following conventional treatment programs. Of late, however, two recently developed interventions - constraint-induced movement therapy (CIMT) and bilateral arm training with rhythmic auditory cueing (BATRAC) - have shown promising results in the treatment of upper limb paresis in chronic stroke patients. The ULTRA-stroke (acronym for Upper Limb TRaining After stroke) program was conceived to assess the effectiveness of these interventions in subacute stroke patients and to examine how the observed changes in sensori-motor functioning relate to changes in stroke recovery mechanisms associated with peripheral stiffness, interlimb interactions, and cortical inter- and intrahemispheric networks. The present paper describes the design of this single blinded randomized clinical trial (RCT), which has recently started and will take several years to complete. METHODS: Sixty patients with a first ever stroke will be recruited. Patients will be stratified in terms of their remaining motor ability at the distal part of the arm (i.e., wrist and finger movements) and randomized over three intervention groups receiving modified CIMT, modified BATRAC, or an equally intensive (i.e., dose-matched) conventional treatment program for 6 weeks. Primary outcome variable is the score on the Action Research Arm test (ARAT), which will be assessed before, directly after, and 6 weeks after the intervention. During those test sessions all patients will also undergo measurements aimed at investigating the associated recovery mechanisms using haptic robots and magneto-encephalography (MEG). DISCUSSION: ULTRA-stroke is a 3-year translational research program which aims (1) to assess the relative effectiveness of the three interventions, on a group level but also as a function of patient characteristics, and (2) to delineate the functional and neurophysiological changes that are induced by those interventions. The outcome on the ARAT together with information about changes in the associated mechanisms will provide a better understanding of how specific therapies influence neurobiological changes, and which post-stroke conditions lend themselves to specific treatments. The ULTRA-stroke program is registered at the Netherlands Trial Register (NTR, http://www.trialregister.nl, number NTR1665).
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1.93Impact points
Corticomuscular and bilateral EMG coherence reflect distinct aspects of neural synchronization.
Neuroscience letters. 08/2009;
Using electroencephalography (EEG) and electromyography (EMG), corticomuscular and bilateral motor unit synchronization have been found in different frequency bands and under different task conditions. These different types of long-range synchrony are hypothesized to originate from distinct mechanis... [more] Using electroencephalography (EEG) and electromyography (EMG), corticomuscular and bilateral motor unit synchronization have been found in different frequency bands and under different task conditions. These different types of long-range synchrony are hypothesized to originate from distinct mechanisms. We tested this by comparing time-resolved EEG-EMG and EMG-EMG coherence in a bilateral precision-grip task. Bilateral EMG activity was synchronized between 7 and 13Hz for about 1s when force output from both hands changed from an increasing to a stable force production. In contrast, EEG-EMG coherence was statistically significant between 15 and 30Hz during stable force production. The disparities in their time-frequency profiles accord with the existence of distinct underlying processes for corticomuscular and bilateral motor unit synchronization. In addition, the absence of synchronization between cortical activity and common spinal input at 10Hz renders a cortical source unlikely.
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2.30Impact points
Functional similarities and distance properties.
Journal of neuroscience methods. 08/2009;
The analysis of functional and effective brain connectivity forms an important tool for unraveling structure-function relationships from neurophysiological data. It has clinical applications, supports the formulation of hypotheses regarding the role and localization of functional processes, and is o... [more] The analysis of functional and effective brain connectivity forms an important tool for unraveling structure-function relationships from neurophysiological data. It has clinical applications, supports the formulation of hypotheses regarding the role and localization of functional processes, and is often an initial step in modeling. However, only a few of the commonly applied connectivity measures respect metric properties: reflexivity, symmetry, and the triangle inequality. This may hamper interpretation of findings and subsequent analysis. Connectivity indices obtained by metric measures can be seen as functional distances, and may be represented in Euclidean space by the methods of multidimensional scaling. We sketch some classes of measures that do allow for such a reconstruction, in particular the class of Wasserstein distances, and discuss their merits for interpreting cortical activity assessed by magnetoencephalography. In an application to magnetoencephalographic recordings during the execution of a bimanual task, the Wasserstein distances between relative circular variances indicated cortico-muscular synchrony as well as cross-talk between bilateral primary motor areas in the beta-band.
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1.93Impact points
Delayed visual feedback reveals distinct time scales in balance control.
Neuroscience letters. 04/2009; 452(1):37-41.
We performed an experiment in which we challenged postural stability in 12 healthy subjects by providing artificial delayed visual feedback. A monitor at eye-height presented subjects with a visual representation of the location of their center-of-pressure (COP) and they were instructed to position ... [more] We performed an experiment in which we challenged postural stability in 12 healthy subjects by providing artificial delayed visual feedback. A monitor at eye-height presented subjects with a visual representation of the location of their center-of-pressure (COP) and they were instructed to position their COP as accurately as possible on a small target. Visual feedback of the COP was displayed either in real-time, or delayed by 250, 500, 750, or 1000 ms. In a control condition, no visual feedback was provided. As expected, stability increased during real-time visual feedback compared to when feedback was absent. To identify time scales at which postural control during quiet stance takes place we sought to distinguish between different frequencies. Low frequencies, i.e. slow components of postural sway, showed a monotonic increase in sway amplitude with increasing delay, whereas high frequencies, i.e. fast components of postural sway, showed significantly reduced sway amplitude for delays of 500-750 ms compared to the other delay conditions. Low- and high-frequency components of postural sway thus exhibited differential susceptibility to artificial delays, thereby supporting the notion of postural control taking place on two distinct time scales.
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3.42Impact points
Bilateral motor unit synchronization of leg muscles during a simple dynamic balance task.
The European journal of neuroscience. 02/2009;
Abstract To handle the rich repertoire of behavioural goals, the CNS has to control the many degrees of freedom of the musculoskeletal system in a flexible manner. This problem can be drastically simplified if muscle synergies serve as the to-be-controlled building blocks of motor performance, inste... [more] Abstract To handle the rich repertoire of behavioural goals, the CNS has to control the many degrees of freedom of the musculoskeletal system in a flexible manner. This problem can be drastically simplified if muscle synergies serve as the to-be-controlled building blocks of motor performance, instead of the individual degrees of freedom. Muscle synergies have been identified as coherent activation patterns of a group of muscles in space or time, but the neural mechanisms underlying their formation remain largely unknown. Here we evaluated the hypothesis that synergies are reflected in common input to different contributing muscles, and investigated modulations in motor unit (MU) synchronization of homologous muscles during a rhythmic balance task. If common input is related to muscle synergies, the resultant MU synchronization should not be static but task dependent and, in the present context, vary in time. Coherence between surface electromyographic signals of bilateral leg muscles revealed MU synchronization in two distinct frequency bands. MU synchronization was not constant but modulated within a movement cycle, and its time course resembled the activation patterns of the muscles. These results are congruent with a linkage between MU synchronization and muscle synergies, and suggest that MU synchronization provides an expedient method for studying synergy-related neural mechanisms.
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2.18Impact points
The effect of surface electric stimulation of the gluteal muscles on the interface pressure in seated people with spinal cord injury.
Archives of physical medicine and rehabilitation. 10/2008; 89(9):1724-32.
OBJECTIVE: To study effects of surface electric stimulation of the gluteal muscles on the interface pressure in seated persons with spinal cord injury (SCI). DESIGN: One session in which alternating and simultaneous surface electric stimulation protocols were applied in random order. SETTING: Resear... [more] OBJECTIVE: To study effects of surface electric stimulation of the gluteal muscles on the interface pressure in seated persons with spinal cord injury (SCI). DESIGN: One session in which alternating and simultaneous surface electric stimulation protocols were applied in random order. SETTING: Research laboratory of a rehabilitation center. PARTICIPANTS: Thirteen subjects with SCI. INTERVENTION: Surface electric stimulation of the gluteal muscles. MAIN OUTCOME MEASURES: Interface pressure, maximum pressure, pressure spread, and pressure gradient for the stimulation measurement. Variables were compared using 2-tailed paired t tests. RESULTS: Alternating and simultaneous stimulation protocol caused a significant (P<.01) decrease in interface pressure (-17+/-12 mmHg, -19+/-14 mmHg) and pressure gradient (-12+/-11 mmHg, -14+/-12 mmHg) during stimulation periods compared with rest periods. There was no significant difference in effects between the 2 protocols. CONCLUSIONS: Surface electric stimulation of the gluteal muscles in persons with SCI causes a decrease in interface pressure. This might restore blood flow in compressed tissue and help prevent pressure ulcers.
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3.48Impact points
Low alcohol doses reduce common 10-15 Hz input to bilateral leg muscles during quiet standing.
Journal of neurophysiology. 09/2008;
The effects of low doses of alcohol on neural synchronization in muscular activity were investigated in ten participants during quiet standing with eyes open or closed. We focused on changes in common input to bilateral motor unit pools as evident in surface EMG recordings of lower leg extensor and ... [more] The effects of low doses of alcohol on neural synchronization in muscular activity were investigated in ten participants during quiet standing with eyes open or closed. We focused on changes in common input to bilateral motor unit pools as evident in surface EMG recordings of lower leg extensor and flexor muscles. The extensor muscles exhibited bilateral synchronization in two distinct frequency bands, i.e., 0-5 and 10-15 Hz, whereas synchronization between flexor muscles was minimal. As expected, alcohol ingestion affected postural sway yielding increased sway at higher blood-alcohol levels. Whereas vision only affected bilateral synchronization at 0-5 Hz, alcohol ingestion resulted in a progressive decrease of synchronization at 10-15 Hz between the EMG activities of the extensor muscles. The decrease in common bilateral input is most likely related to reduced reticulospinal activity with alcohol ingestion.
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1.60Impact points
Extracting global and local dynamics from the stochastics of rhythmic forearm movements.
Journal of motor behavior. 06/2008; 40(3):214-31.
The authors examined the dynamics governing rhythmic forearm movements that 9 participants performed under a variety of task constraints by using a generic, unbiased analysis technique for extracting the drift coefficients of Fokker-Planck equations from stochastic data. From those coefficients, the... [more] The authors examined the dynamics governing rhythmic forearm movements that 9 participants performed under a variety of task constraints by using a generic, unbiased analysis technique for extracting the drift coefficients of Fokker-Planck equations from stochastic data. From those coefficients, they reconstructed and analyzed vector fields and phase portraits to identify characteristic, task-dependent kinematic and dynamical features. They first directly estimated the parameters of weakly nonlinear self-sustaining oscillators from the extracted drift coefficients. The estimated parameters that the authors had selected instinctively and then particularized by using averaging methods largely confirmed previously derived limit-cycle models. Next, they ventured beyond limit-cycle models to examine global and local dynamical features that those models cannot adequately address, particularly task-dependent changes in flow strength and curvature and distinct dynamical features associated with flexion and extension. The authors argue that those features should be focal points of researchers' future modeling efforts to formulate a more adequate and encompassing account of the dynamics of rhythmic movement.
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1.93Impact points
Characteristics of instructed and uninstructed interpersonal coordination while walking side-by-side.
Neuroscience letters. 03/2008; 432(2):88-93.
We examined how people synchronize their leg movements while walking side-by-side on a treadmill. Walker pairs were either instructed to synchronize their steps in in-phase or in antiphase or received no coordination instructions. Frequency and phase analysis revealed that instructed in-phase and an... [more] We examined how people synchronize their leg movements while walking side-by-side on a treadmill. Walker pairs were either instructed to synchronize their steps in in-phase or in antiphase or received no coordination instructions. Frequency and phase analysis revealed that instructed in-phase and antiphase coordination were equally stable and independent of walking speed and the difference in individually preferred stride frequencies. Without instruction we found episodes of frequency locking in three pairs and episodes of phase locking in four pairs, albeit not always at (or near) 0 degrees or 180 degrees. Again, we found no difference in the stability of in-phase and antiphase coordination and no systematic effects of walking speed and the difference in individually preferred stride frequencies. These results suggest that the Haken-Kelso-Bunz model for rhythmic interlimb coordination does not apply to interpersonal coordination during gait in a straightforward manner. When the typically involved parameter constraints are relaxed, however, this model may largely account for the observed dynamical characteristics.
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2.41Impact points
Impairment of complex upper limb motor function in de novo Parkinson's disease.
Parkinsonism & related disorders. 02/2008; 14(3):199-204.
The aim of the present study was to evaluate complex upper limb motor function in newly diagnosed, untreated Parkinson's disease (PD) patients. Four different unimanual upper limb motor tasks were applied to 13 newly diagnosed, untreated PD patients and 13 age- and sex-matched controls. In a han... [more] The aim of the present study was to evaluate complex upper limb motor function in newly diagnosed, untreated Parkinson's disease (PD) patients. Four different unimanual upper limb motor tasks were applied to 13 newly diagnosed, untreated PD patients and 13 age- and sex-matched controls. In a handwriting task, PD patients had significantly reduced sentence length and writing velocity, and decreasing letter height in the course of writing. Furthermore, PD patients performed an aiming task slower with than without target, and showed increased transposition in a pointing task. The results of this study extend previous observations of impaired complex upper limb movements to newly diagnosed, untreated PD patients.
Following (5)
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Sjoerd Verduyn-Lunel
Universiteit Leiden -
Michael Muskulus
Norwegian University of Science and Technology (NTNU) -
Nienke Willigenburg
VU University Amsterdam -
Guido Nolte
Fraunhofer -
Dick F Stegeman
UMC St Radboud
