References of "Garraux, Gaëtan"
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See detailMapping track density changes in nigrostriatal and extranigral pathways in Parkinson's disease
Ziegler, Erik ULg; Rouillard, Maud; André, Elodie et al

in NeuroImage (in press)

Highlights First whole-brain probabilistic tractography study in Parkinson's disease High quality diffusion-weighted images (120 gradient directions, b = 2500 s/mm2) Voxel-based group analysis comparing ... [more ▼]

Highlights First whole-brain probabilistic tractography study in Parkinson's disease High quality diffusion-weighted images (120 gradient directions, b = 2500 s/mm2) Voxel-based group analysis comparing early-stage patients and controls Abnormal reconstructed track density in the nigrostriatal pathway and brainstem Track density also increased in limbic and cognitive circuits. [less ▲]

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See detailValidation des paramètres de marche par un système accélérométrique (Locométrix*) à l'aide d'un système opto-électronique 3D (Coda Motion )
GILLAIN, Sophie ULg; Schwartz, Cédric ULg; Boutaayamou, Mohamed ULg et al

in Gériatrie et Psychologie Neuropsychiatrie du Vieillissement (2014), 12(supplément 3),

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See detailQuantitative multi-parameter mapping in parkinson’s disease: preliminary results
Rouillard, Maud ULg; D'Ostilio, Kevin ULg; Albinet, Cedric et al

Poster (2014, May)

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See detailBiased binomial assessment of cross-validated estimation of classification accuracies illustrated in diagnosis predictions
Noirhomme, Quentin ULg; Lesenfants, Damien ULg; Gomez, Francisco et al

in NeuroImage: Clinical (2014), 4

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a ... [more ▼]

Multivariate classification is used in neuroimaging studies to infer brain activation or in medical applications to infer diagnosis. Their results are often assessed through either a binomial or a permutation test. Here, we simulated classification results of generated random data to assess the influence of the cross-validation scheme on the significance of results. Distributions built from classification of random data with crossvalidation did not follow the binomial distribution. The binomial test is therefore not adapted. On the contrary, the permutation test was unaffected by the cross-validation scheme. The influence of the crossvalidation was further illustrated on real-data from a brain–computer interface experiment in patients with disorders of consciousness and from an fMRI study on patients with Parkinson disease. Three out of 16 patients with disorders of consciousness had significant accuracy on binomial testing, but only one showed significant accuracy using permutation testing. In the fMRI experiment, the mental imagery of gait could discriminate significantly between idiopathic Parkinson’s disease patients and healthy subjects according to the permutation test but not according to the binomial test. Hence, binomial testing could lead to biased estimation of significance and false positive or negative results. In our view, permutation testing is thus recommended for clinical application of classification with cross-validation. [less ▲]

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See detailValidation des paramètres de marche par un système accélérométrique (Locométrix) à l’aide d’un système opto-électronique 3D (Coda Motion)
GILLAIN, Sophie ULg; Schwartz, C; Dramé, M et al

in Les Cahiers de l'Année Gérontologique (2014), 2(23), 724-73

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See detail3D analysis of gait using accelerometer measurements
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

Scientific conference (2013, November 07)

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See detailEVALUATION OF α-SYNUCLEIN AS BIOMARKER OF PARKINSON'S DISEASE
Napp, Aurore ULg; Garraux, Gaëtan ULg; Servais, Anne-Catherine ULg et al

Conference (2013, October 17)

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See detailStrength improvement after 3months of resistance training among Parkinson's disease patients
Demonceau, Marie ULg; rodriguez de la cruz, carlos; NAVEAU, Florence ULg et al

in Annals of Physical and Rehabilitation Medicine (2013, October), 56(s1), 196

Objectives.– To assess the feasibility and the effects of a strengthening program for people with Parkinson's disease (PD). Methods.– Fourteen patients with Hoehn and Yahr stage [1] < III of PD were ... [more ▼]

Objectives.– To assess the feasibility and the effects of a strengthening program for people with Parkinson's disease (PD). Methods.– Fourteen patients with Hoehn and Yahr stage [1] < III of PD were allocated to either 24 sessions of strength training (ST group; n = 8) or to a control group (C group; n = 6) for 3 months. Concentric knee muscle strength and a maximal cycling incremental test were performed at baseline and after training. Training consisted of progressive resistive exercises on leg press, leg extension, leg curl, between 50 and 80% of 1RM and was completed by non-instrumented exercises for trunk and upper limbs muscles. Anxiety, depression and quality of life were assessed using questionnaires. An Anova for repeated measures was used for statistical analysis. Results.– Six patients of the ST group (75%) fully completed the program. There were significant “group by time” effects for all knee muscles strength measures of less involved side (P < 0.05). A significant “group by time” effect was also found for knee flexors of the most involved side, but only at angular speed of 180°/s (P = 0.03). Patients of ST group also increased maximal aerobic power (+13%) whereas patients of C group decreased their performances (–9%; “group by time” effect, P = 0.04). No changes in anxiety, depression or quality of life could be highlighted. Conclusions.– The increase of some strength measures in ST group showed that progressive strength training counteracts strength decrease among people with Parkinson's disease. Strengthening also had a positive effect on maximal aerobic power. [less ▲]

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See detailEffects of 3 months of aerobic training on fitness of Parkinson's disease patients
Demonceau, Marie ULg; rodriguez de la Cruz, carlos; kalimira, kinja et al

in Annals of Physical and Rehabilitation Medicine (2013)

Objectives.– To assess the effects of an aerobic training for people with Parkinson's disease (PD). Methods.– Fourteen patients with Hoehn & Yahr stage [1] < III of PD were allocated to either 3 months of ... [more ▼]

Objectives.– To assess the effects of an aerobic training for people with Parkinson's disease (PD). Methods.– Fourteen patients with Hoehn & Yahr stage [1] < III of PD were allocated to either 3 months of twice-weekly aerobic training (AT group; n = 8), or a control group (C group; n = 6). AT consisted in progressive stationary bike training between 50 and 70% of peak work load (PWL). Maximal incremental test on a cycloergometer was performed before and after rehabilitation. Anxiety, depression and quality of life were assessed using questionnaires. An Anova for repeated measures was used for statistical analysis. Results.– There was a significant “group by time” effect for peak work load (+21% for patients of AT group vs –9% for people of C group). Heart rate 2 minutes after test completion was also significantly decreased in AT group (post hoc analysis, P < 0.01). Patients of AT group also increased their ratio of predicted VO2 peak (+17%) but in a non-significant way. No significant changes in anxiety, depression or quality of life could be highlighted. Conclusions.– This study showed significant improvement of PWL and faster recovery in patients with PD of the AT. Significant effect on VO2 peak could need a more intense training program. [less ▲]

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See detailImpaired automatic and unconscious motor processes in Parkinson's disease
D'Ostilio, Kevin ULg; CREMERS, Julien ULg; DELVAUX, Valérie ULg et al

in Scientific Reports (2013)

While it is increasingly recognized that voluntary movements are produced by an interaction between conscious and unconscious processes, the role of the latter in Parkinson’s disease has received little ... [more ▼]

While it is increasingly recognized that voluntary movements are produced by an interaction between conscious and unconscious processes, the role of the latter in Parkinson’s disease has received little attention to date. Here, we administered a subliminal masked prime task to 15 Parkinson’s disease patients and 15 age-matched healthy elderly subjects. Compatibility effects were examined by manipulating the direction of the arrows and the interstimuli interval. Analysis of the positive compatibility effect revealed performance differences between the most and the least affected hand in Parkinson’s disease patients. Additionally, patients did not show the same tendency toward a negative compatibility effect as compared to elderly controls. These novel findings provide evidence supporting the role of basal ganglia circuits in controlling the balance between automatic motor response facilitation and inhibition. [less ▲]

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See detailValidation of an accelerometer-based approach to quantify gait events
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

Poster (2013, June)

Researchers rarely provide solid performance and validation information about their acceleometer-based approaches to human gait analysis. We present here a novel signal processing and analysis algorithm ... [more ▼]

Researchers rarely provide solid performance and validation information about their acceleometer-based approaches to human gait analysis. We present here a novel signal processing and analysis algorithm that automatically extracts four consecutive fundamental events of walking: heel strike (HS), toe strike (TS), heel off (HO), and toe off (TO). In addition, we validate this accelerometer-based technique by comparing these extracted gait events with those obtained by a kinematic 3D analysis system and a force plate, used as gold standards. [less ▲]

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See detailLes troubles du contrôle des impulsions associés au traitement dopaminergique substitutif antiparkinsonien
DEPIERREUX, Frédérique ULg; CREMERS, Julien ULg; SKAWINIAK, Eva ULg et al

in Revue Médicale de Liège (2013), 68(mai-juin), 221-225

Summary : In some patients, impulse control behaviours can be triggered by dopaminergic replacement therapy, particularly dopamine agonist drugs: hobbyism, punding (stereotyped behaviours), compulsive ... [more ▼]

Summary : In some patients, impulse control behaviours can be triggered by dopaminergic replacement therapy, particularly dopamine agonist drugs: hobbyism, punding (stereotyped behaviours), compulsive buying, binge eating disorder, pathological gamgling, hypersexuality, hedonistic homeostatic dysregulation syndrome ... The pathogenesis of these behaviours is not well understood, but likely involves aberrant changes in the dopaminergic pathways that mediate motivation i.e., a dopaminergic “overdose” in meso-cortico-limbic circuits. An early diagnosis is difficult, but mandatory to prevent the occurrence of devastating familial, marital, professional, socio-economic, medical and medico-legal consequences. Their management is not yet well standardized. Patients and caregivers should be warned about impulse control behaviours before starting dopamine agonists and monitoring for such behaviours while on therapy is requested. [less ▲]

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See detailAn intervention study on physical activity and cognitive functioning in people with Parkinson’s disease
Rouillard, Maud ULg; Audiffren, Michel; Albinet, Cédric et al

Poster (2013)

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See detailMulticlass classification of FDG PET scans for the distinction between Parkinson's disease and atypical parkinsonian syndromes
Garraux, Gaëtan ULg; Phillips, Christophe ULg; Schrouff, Jessica ULg et al

in NeuroImage: Clinical (2013), 2

Most available pattern recognition methods in neuroimaging address binary classification problems. Here, we used relevance vector machine (RVM) in combination with booststrap resampling (‘bagging’) for ... [more ▼]

Most available pattern recognition methods in neuroimaging address binary classification problems. Here, we used relevance vector machine (RVM) in combination with booststrap resampling (‘bagging’) for non-hierarchical multiclass classification. The method was tested on 120 cerebral 18fluorodeoxyglucose (FDG) positron emission tomography (PET) scans performed in patients who exhibited parkinsonian clinical features for 3.5 years on average but that were outside the prevailing perception for Parkinson's disease (PD). A radiological diagnosis of PD was suggested for 30 patients at the time of PET imaging. However, at follow-up several years after PET imaging, 42 of them finally received a clinical diagnosis of PD. The remaining 78 APS patients were diagnosed with multiple system atrophy (MSA, N = 31), progressive supranuclear palsy (PSP, N = 26) and corticobasal syndrome (CBS, N = 21), respectively. With respect to this standard of truth, classification sensitivity, specificity, positive and negative predictive values for PD were 93% 83% 75% and 96%, respectively using binary RVM (PD vs. APS) and 90%, 87%, 79% and 94%, respectively, using multiclass RVM (PD vs. MSA vs. PSP vs. CBS). Multiclass RVM achieved 45%, 55% and 62% classification accuracy for, MSA, PSP and CBS, respectively. Finally, a majority confidence ratio was computed for each scan on the basis of class pairs that were the most frequently assigned by RVM. Altogether, the results suggest that automatic multiclass RVM classification of FDG PET scans achieves adequate performance for the early differentiation between PD and APS on the basis of cerebral FDG uptake patterns when the clinical diagnosis is felt uncertain. This approach cannot be recommended yet as an aid for distinction between the three APS classes under consideration. [less ▲]

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See detailLocalizing and comparing weight maps generated from linear kernel machine learning models
Schrouff, Jessica ULg; CREMERS, Julien ULg; GARRAUX, Gaëtan ULg et al

in 2013 Third International Workshop on Pattern Recognition in NeuroImaging (PRNI 2013): proceedings (2013)

Recently, machine learning models have been applied to neuroimaging data, allowing to make predictions about a variable of interest based on the pattern of activation or anatomy over a set of voxels ... [more ▼]

Recently, machine learning models have been applied to neuroimaging data, allowing to make predictions about a variable of interest based on the pattern of activation or anatomy over a set of voxels. These pattern recognition based methods present undeniable assets over classical (univariate) techniques, by providing predictions for unseen data, as well as the weights of each voxel in the model. However, the obtained weight map cannot be thresholded to perform regionally specific inference, leading to a difficult localization of the variable of interest. In this work, we provide local averages of the weights according to regions defined by anatomical or functional atlases (e.g. Brodmann atlas). These averages can then be ranked, thereby providing a sorted list of regions that can be (to a certain extent) compared with univariate results. Furthermore, we defined a “ranking distance”, allowing for the quantitative comparison between localized patterns. These concepts are illustrated with two datasets. [less ▲]

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