Bernard Dan

Hôpital Universitaire des Enfants Reine Fabiola, Bruxelles, Brussels Capital Region, Belgium

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Publications (208)474.6 Total impact

  • Bernard Dan
    Developmental Medicine & Child Neurology 09/2014; · 2.68 Impact Factor
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    ABSTRACT: The continuation of binge drinking is associated with the development of neurocognitive brain abnormalities similar to those observed in patients with alcohol dependence. Alcohol cue reactivity constitutes a risk marker for alcohol dependence. Through event-related potentials (ERPs), we aimed to examine its potential presence as well as its evolution over time in binge drinkers in a one-year period.
    Journal of psychopharmacology (Oxford, England). 08/2014;
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    ABSTRACT: The N30 component of the somatosensory evoked potential is known to be modulated by sensory interference, motor action, movement ideation and observation. We introduce a new paradigm in which the observation task of another person's hand movement triggers the somatosensory stimulus, inducing the N30 response in participants. In order to identify the possible contribution of the mirror neuron network (MNN) to this early sensorimotor processing, we analyzed the N30 topography, the event-related spectral perturbation and the inter-trial coherence on single electroencephalogram (EEG) trials, and we applied swLORETA to localize the N30 sources implicated in the time-frequency domain at rest and during observation, as well as the generators differentiating these two contextual brain states. We found that N30 amplitude increase correlated with increased contralateral precentral alpha, frontal beta, and contralateral frontal gamma power spectrum, and with central and precentral alpha and parietal beta phase-locking of ongoing EEG signals. We demonstrate specific activation of the contralateral postcentral and parietal cortex where the angular gyrus (BA39), an important MNN node, is implicated in this enhancement during observation. We conclude that this part of the MNN, involved in proprioceptive processing and more complex body-action representations, is already active prior to somatosensory input and may enhance N30.
    NeuroImage 03/2014; · 6.25 Impact Factor
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    ABSTRACT: AimThe first aim of this study was to systematically review and critically assess manually controlled instrumented spasticity assessment methods that combine multidimensional signals. The second aim was to extract a set of quantified parameters that are psychometrically sound to assess spasticity in a clinical setting.Method Electronic databases were searched to identify studies that assessed spasticity by simultaneously collecting electrophysiological and biomechanical signals during manually controlled passive muscle stretches. Two independent reviewers critically assessed the methodological quality of the psychometric properties of the included studies using the COSMIN guidelines.ResultsFifteen studies with instrumented spasticity assessments met all inclusion criteria. Parameters that integrated electrophysiological signals with joint movement characteristics were best able to quantify spasticity. There were conflicting results regarding biomechanical-based parameters that quantify the resistance to passive stretch. Few methods have been assessed for all psychometric properties. In particular, further information on absolute reliability and responsiveness for more muscles is needed.InterpretationFurther research is required to determine the correct parameters for quantifying spasticity based on integration of signals, which especially focuses on distinguishing the neural from non-neural contributions to increased joint torque. These parameters should undergo more rigorous exploration to establish their psychometric properties for use in a clinical environment.
    Developmental Medicine & Child Neurology 03/2014; · 2.68 Impact Factor
  • The Lancet 02/2014; 383(9918):671-2. · 39.21 Impact Factor
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    ABSTRACT: Purkinje cell (PC) firing represents the sole output from the cerebellar cortex onto the deep cerebellar and vestibular nuclei. Here, we explored the different modes of PC firing in alert mice by extracellular recording. We confirm the existence of a tonic and/or bursting and quiescent modes corresponding to UP and DOWN state, respectively. We demonstrate the existence of a novel 600 Hz-buzz UP state of firing characterized by simple spikes (SS) of very small amplitude. Climbing fiber (CF) input is able to switch the 600 Hz-buzz to the DOWN state, as for the classical UP-to-DOWN state transition. Conversely, the CF input can initiate a typical SS pattern terminating into 600 Hz-buzz. The 600 Hz-buzz was transiently suppressed by whisker pad stimulation demonstrating that it remained responsive to peripheral input. It must not be mistaken for a DOWN state or the sign of PC inhibition. Complex spike (CS) frequency was increased during the 600 Hz-buzz, indicating that this PC output actively contributes to the cerebello-olivary loop by triggering a disinhibition of the inferior olive. During the 600 Hz-buzz, the first depolarizing component of the CS was reduced and the second depolarizing component was suppressed. Consistent with our experimental observations, using a 559-compartment single-PC model - in which PC UP state (of about -43 mV) was obtained by the combined action of large tonic AMPA conductances and counterbalancing GABAergic inhibition - removal of this inhibition produced the 600 Hz-buzz; the simulated buzz frequency decreased following an artificial CS.
    Neuroscience 01/2014; · 3.12 Impact Factor
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    Bernard Dan, Peter Baxter
    The Lancet Neurology 01/2014; 13(1):16-18. · 23.92 Impact Factor
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    ABSTRACT: Visual perception is not only based on incoming visual signals but also on information about a multimodal reference frame that incorporates vestibulo-proprioceptive input and motor signals. In addition, top-down modulation of visual processing has previously been demonstrated during cognitive operations including selective attention and working memory tasks. In the absence of a stable gravitational reference, the updating of salient stimuli becomes crucial for successful visuo-spatial behavior by humans in weightlessness. Here we found that visually-evoked potentials triggered by the image of a tunnel just prior to an impending 3D movement in a virtual navigation task were altered in weightlessness aboard the International Space Station, while those evoked by a classical 2D-checkerboard were not. Specifically, the analysis of event-related spectral perturbations and inter-trial phase coherency of these EEG signals recorded in the frontal and occipital areas showed that phase-locking of theta-alpha oscillations was suppressed in weightlessness, but only for the 3D tunnel image. Moreover, analysis of the phase of the coherency demonstrated the existence on Earth of a directional flux in the EEG signals from the frontal to the occipital areas mediating a top-down modulation during the presentation of the image of the 3D tunnel. In weightlessness, this fronto-occipital, top-down control was transformed into a diverging flux from the central areas toward the frontal and occipital areas. These results demonstrate that gravity-related sensory inputs modulate primary visual areas depending on the affordances of the visual scene.
    PLoS ONE 01/2014; 9(1):e82371. · 3.53 Impact Factor
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    ABSTRACT: Biological motion observation has been recognized to produce dynamic change in sensorimotor activation according to the observed kinematics. Physical plausibility of the spatial-kinematic relationship of human movement may play a major role in the top-down processing of human motion recognition. Here, we investigated the time course of scalp activation during observation of human gait in order to extract and use it on future integrated brain-computer interface using virtual reality (VR). We analyzed event related potentials (ERP), the event related spectral perturbation (ERSP) and the inter-trial coherence (ITC) from high-density EEG recording during video display onset (-200-600 ms) and the steady state visual evoked potentials (SSVEP) inside the video of human walking 3D-animation in three conditions: Normal; Upside-down (inverted images); and Uncoordinated (pseudo-randomly mixed images). We found that early visual evoked response P120 was decreased in Upside-down condition. The N170 and P300b amplitudes were decreased in Uncoordinated condition. In Upside-down and Uncoordinated conditions, we found decreased alpha power and theta phase-locking. As regards gamma oscillation, power was increased during the Upside-down animation and decreased during the Uncoordinated animation. An SSVEP-like response oscillating at about 10 Hz was also described showing that the oscillating pattern is enhanced 300 ms after the heel strike event only in the Normal but not in the Upside-down condition. Our results are consistent with most of previous point-light display studies, further supporting possible use of virtual reality for neurofeedback applications.
    Frontiers in Systems Neuroscience 01/2014; 8:169.
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    ABSTRACT: In this study we employed a dynamic recurrent neural network (DRNN) in a novel fashion to reveal characteristics of control modules underlying the generation of muscle activations when drawing figures with the outstretched arm. We asked healthy human subjects to perform four different figure-eight movements in each of two workspaces (frontal plane and sagittal plane). We then trained a DRNN to predict the movement of the wrist from information in the EMG signals from seven different muscles. We trained different instances of the same network on a single movement direction, on all four movement directions in a single movement plane, or on all eight possible movement patterns and looked at the ability of the DRNN to generalize and predict movements for trials that were not included in the training set. Within a single movement plane, a DRNN trained on one movement direction was not able to predict movements of the hand for trials in the other three directions, but a DRNN trained simultaneously on all four movement directions could generalize across movement directions within the same plane. Similarly, the DRNN was able to reproduce the kinematics of the hand for both movement planes, but only if it was trained on examples performed in each one. As we will discuss, these results indicate that there are important dynamical constraints on the mapping of EMG to hand movement that depend on both the time sequence of the movement and on the anatomical constraints of the musculoskeletal system. In a second step, we injected EMG signals constructed from different synergies derived by the PCA in order to identify the mechanical significance of each of these components. From these results, one can surmise that discrete-rhythmic movements may be constructed from three different fundamental modules, one regulating the co-activation of all muscles over the time span of the movement and two others elliciting patterns of reciprocal activation operating in orthogonal directions.
    Frontiers in Computational Neuroscience 01/2014; 8:100. · 2.48 Impact Factor
  • European journal of paediatric neurology: EJPN: official journal of the European Paediatric Neurology Society 09/2013; 17(S1):S32. · 2.01 Impact Factor
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    ABSTRACT: Identification and diagnosis of autism spectrum disorders is essentially based on behavioral presentation and developmental history. The current average age at diagnosis is older than 3 years. Over the past 15 years, there has been increasing documentation of the early signs of autism spectrum disorders through both individual retrospective parental reports and screening studies. Recent longitudinal studies have focused on early medical and behavioral features of children regarded at risk, namely younger siblings of children with autism spectrum disorders or children who required neonatal intensive care, with a later diagnosis of autism spectrum disorders. Potentially useful early neurological signs and developmental predictors for autism spectrum disorders could be identified, with a typical profile that evolved with age. Assessment of early social attention and communication skills with adapted scales in children before the age of 18 months in very large community-based settings may lead to high positive predictive values.
    Pediatric Neurology 08/2013; · 1.42 Impact Factor
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    ABSTRACT: The musculoskeletal system (MSS) is essential to allow us performing every-day tasks, being able to have a professional life or developing social interactions with our entourage. MSS pathologies have a significant impact on our daily life. It is therefore not surprising to find MSS-related health problems at the top of global statistics on professional absenteeism or societal health costs. The MSS is also involved in central nervous conditions, such as cerebral palsy (CP). Such conditions show complex etiology that complicates the interpretation of the observable clinical signs and the establishment of a wide consensus on the best practices to adopt for clinical monitoring and patient follow-up. These elements justify the organization of fundamental and applied research projects aiming to develop new methods to help clinicians to cope with the complexity of some MSS disorders. The ICT4Rehab project (www.ict4rehab.org) developed an integrated platform providing tools that enable easier management and visualization of clinical information related to the MSS of CP patients. This platform is opened to every interested clinical centre.
    Medecine sciences: M/S 05/2013; 29(5):529-36. · 0.56 Impact Factor
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    ABSTRACT: Botulinum toxin injections may significantly improve lower limb kinematics in gait of children with spastic forms of cerebral palsy. Here we aimed to analyze the effect of lower limb botulinum toxin injections on trunk postural control and lower limb intralimb (intersegmental) coordination in children with spastic diplegia or spastic hemiplegia (GMFCS I or II). We recorded tridimensional trunk kinematics and thigh, shank and foot elevation angles in fourteen 3-12 year-old children with spastic diplegia and 14 with spastic hemiplegia while walking either barefoot or with ankle-foot orthoses (AFO) before and after botulinum toxin infiltration according to a management protocol. We found significantly greater trunk excursions in the transverse plane (barefoot condition) and in the frontal plane (AFO condition). Intralimb coordination showed significant differences only in the barefoot condition, suggesting that reducing the degrees of freedom may limit the emergence of selective coordination. Minimal relative phase analysis showed differences between the groups (diplegia and hemiplegia) but there were no significant alterations unless the children wore AFO. We conclude that botulinum toxin injection in lower limb spastic muscles leads to changes in motor planning, including through interference with trunk stability, but a combination of therapies (orthoses and physical therapy) is needed in order to learn new motor strategies.
    Toxins 01/2013; 5(1):93-105. · 2.13 Impact Factor
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    ABSTRACT: The existence of dedicated neuronal modules such as those organized in the cerebral cortex, thalamus, basal ganglia, cerebellum, or spinal cord raises the question of how these functional modules are coordinated for appropriate motor behavior. Study of human locomotion offers an interesting field for addressing this central question. The coordination of the elevation of the 3 leg segments under a planar covariation rule (Borghese et al., 1996) was recently modeled (Barliya et al., 2009) by phase-adjusted simple oscillators shedding new light on the understanding of the central pattern generator (CPG) processing relevant oscillation signals. We describe the use of a dynamic recurrent neural network (DRNN) mimicking the natural oscillatory behavior of human locomotion for reproducing the planar covariation rule in both legs at different walking speeds. Neural network learning was based on sinusoid signals integrating frequency and amplitude features of the first three harmonics of the sagittal elevation angles of the thigh, shank, and foot of each lower limb. We verified the biological plausibility of the neural networks. Best results were obtained with oscillations extracted from the first three harmonics in comparison to oscillations outside the harmonic frequency peaks. Physiological replication steadily increased with the number of neuronal units from 1 to 80, where similarity index reached 0.99. Analysis of synaptic weighting showed that the proportion of inhibitory connections consistently increased with the number of neuronal units in the DRNN. This emerging property in the artificial neural networks resonates with recent advances in neurophysiology of inhibitory neurons that are involved in central nervous system oscillatory activities. The main message of this study is that this type of DRNN may offer a useful model of physiological central pattern generator for gaining insights in basic research and developing clinical applications.
    Frontiers in Computational Neuroscience 01/2013; 7:70. · 2.48 Impact Factor
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    ABSTRACT: Diagnosis and most of all classification of children with cerebral palsy (CP) remain a challenge for clinicians. To help them in this process, clinicians can rely on several clinical testing procedures as well as complementary investigations. The goal of this study was to determine which clinical tests found in the literature are the most frequently used in common practice in Belgium. Forty tests have been found in the literature. They have been sorted into five different categories: quantitative evaluation of motor function, spasticity evaluation, orthopaedic testing, upper limb evaluation and complementary investigations. Seven clinicians (five medical doctors and two physiotherapists) with a mean experience of sixteen years with CP children answered the questionnaire. Concerning the quantitative evaluation of motor function the most used tests are: Gross Motor Function Classification System, Manual Ability Classification System and the Pediatric Evaluation of Disability Inventory (PEDI). As regards spasticity, Ashworth scale is more frequently used than Tardieu test. No trend currently exist for the upper limb evaluation, but it was noted that these tests are rarely used in clinical practice. We observed a significant use of gait analysis at diagnosis and follow-up of CP children. We conclude that there are large differences between clinicians for clinical examination of CP children. This lack of consensus makes patient data comparison difficult between clinical centers. This seems to indicate that a homogenization effort should be organized if one wishes to better stimulate collaborations between centers.
    Revue medicale de Bruxelles 01/2013; 34(2):70-8.
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    ABSTRACT: The role of cerebellar plasticity has been increasingly recognized in learning. The privileged relationship between the cerebellum and the inferior olive offers an ideal circuit for attempting to integrate the numerous evidences of neuronal plasticity into a translational perspective. The high learning capacity of the Purkinje cells specifically controlled by the climbing fiber represents a major element within the feed-forward and feedback loops of the cerebellar cortex. Reciprocally connected with the basal ganglia and multimodal cerebral domains, this cerebellar network may realize fundamental functions in a wide range of behaviors. This review will outline the current understanding of three main experimental paradigms largely used for revealing cerebellar functions in behavioral learning: (1) the vestibuloocular reflex and smooth pursuit control, (2) the eyeblink conditioning, and (3) the sensory envelope plasticity. For each of these experimental conditions, we have critically revisited the chain of causalities linking together neural circuits, neural signals, and plasticity mechanisms, giving preference to behaving or alert animal physiology. Namely, recent experimental approaches mixing neural units and local field potentials recordings have demonstrated a spike timing dependent plasticity by which the cerebellum remains at a strategic crossroad for deciphering fundamental and translational mechanisms from cellular to network levels.
    Neural Plasticity 01/2013; 2013:853654. · 2.86 Impact Factor
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    ABSTRACT: Most clinical tools for measuring spasticity, such as the Modified Ashworth Scale (MAS) and the Modified Tardieu Scale (MTS), are not sufficiently accurate or reliable. This study investigated the clinimetric properties of an instrumented spasticity assessment. Twenty-eight children with spastic cerebral palsy (CP) and 10 typically developing (TD) children were included. Six of the children with CP were retested to evaluate reliability. To quantify spasticity in the gastrocnemius (GAS) and medial hamstrings (MEH), three synchronized signals were collected and integrated: surface electromyography (sEMG); joint-angle characteristics; and torque. Muscles were manually stretched at low velocity (LV) and high velocity (HV). Spasticity parameters were extracted from the change in sEMG and in torque between LV and HV. Reliability was determined with intraclass-correlation coefficients and the standard error of measurement; validity by assessing group differences and correlating spasticity parameters with the MAS and MTS. Reliability was moderately high for both muscles. Spasticity parameters in both muscles were higher in children with CP than in TD children, showed moderate correlation with the MAS for both muscles and good correlation to the MTS for the MEH. Spasticity assessment based on multidimensional signals therefore provides reliable and clinically relevant measures of spasticity. Moreover, the moderate correlations of the MAS and MTS with the objective parameters further stress the added value of the instrumented measurements to detect and investigate spasticity, especially for the GAS.
    Gait & posture 12/2012; · 2.58 Impact Factor
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    ABSTRACT: BACKGROUND: The Dyskinesia Impairment Scale (DIS) is a new scale for measuring dystonia and choreoathetosis in dyskinetic Cerebral Palsy (CP). Previously, reliability of this scale has only been assessed for raters highly experienced in discriminating between dystonia and choreoathetosis. AIMS: The aims of this study are to examine the reliability of the DIS used by inexperienced raters, new to discriminating between dystonia and choreoathetosis and to determine the effect of clinical expertise on reliability. METHODS: Twenty-five patients (17 males; 8 females; age range 5-22 years; mean age = 13 years 6 months; SD = 5 years 4 months) with dyskinetic CP were filmed with the DIS standard video protocol. Two junior physiotherapists (PTs) and three senior PTs, all of whom were new to discriminating between dystonia and choreoathetosis, were trained in scoring the DIS. Afterward, they independently scored all patients from the video recordings using the DIS. Reliability was assessed by (1) Intraclass Correlation Coefficient (ICC), (2) Standard Error of Measurement (SEM) and Minimal Detectable Difference (MDD) and (3) Cronbach's alpha for internal consistency. RESULTS: Interrater reliability for the total DIS, and for the dystonia and choreoathetosis subscales was good for the junior PTs and moderately high to excellent for the senior PTs. SEM and MDD values for the total DIS were 6% and 15% respectively for the junior PTs and 4% and 12% respectively for the senior PTs. Cronbach's alpha ranged between 0.87 and 0.95 for the junior PTs and between 0.76 and 0.93 for the senior PTs. CONCLUSIONS: Reliability of the DIS scores for the inexperienced junior and senior PTs was sufficient in comparison with scores from the experienced raters in the previous study, indicating that the DIS can be used by inexperienced PTs new to discriminating between dystonia and choreoathetosis, and also that its reliability is not dependent on clinical expertise. However, based on the measurement errors and questionnaire data, familiarity with operational definitions of dystonia and choreoathetosis is crucial to improve scoring reliability.
    European journal of paediatric neurology: EJPN: official journal of the European Paediatric Neurology Society 11/2012; · 2.01 Impact Factor
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    Bernard Dan, Ellie Smith
    Developmental Medicine & Child Neurology 08/2012; 54(8):675. · 2.68 Impact Factor

Publication Stats

2k Citations
474.60 Total Impact Points

Institutions

  • 1999–2014
    • Hôpital Universitaire des Enfants Reine Fabiola
      • Department of Neurology
      Bruxelles, Brussels Capital Region, Belgium
  • 1998–2014
    • Université Libre de Bruxelles
      • • Laboratory of Neurophysiology and Movement Biomechanics (LNMB)
      • • Department of Nephrology and Urology
      • • Department of Psychiatry
      • • Laboratory of Neurophysiology
      Bruxelles, Brussels Capital Region, Belgium
  • 2012
    • Maastricht University
      • Genetica en Celbiologie
      Maastricht, Provincie Limburg, Netherlands
  • 1999–2011
    • Vrije Universiteit Brussel
      • • Department of Psychiatry
      • • Department of Neurology
      Bruxelles, Brussels Capital Region, Belgium
  • 2005
    • Université de Mons
      Mons, Walloon Region, Belgium
  • 2002–2004
    • University-Hospital Brugmann UVC
      Bruxelles, Brussels Capital Region, Belgium
    • Great Ormond Street Hospital for Children NHS Foundation Trust
      • Department of Neurophysiology
      Londinium, England, United Kingdom