Publications of Julien CREMERS
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See detailImpaired automatic and unconscious motor processes in Parkinson's disease
D'Ostilio, Kevin ULiege; CREMERS, Julien ULiege; DELVAUX, Valérie ULiege 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 detailLes troubles du contrôle des impulsions associés au traitement dopaminergique substitutif antiparkinsonien
DEPIERREUX, Frédérique ULiege; CREMERS, Julien ULiege; SKAWINIAK, Eva ULiege 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 detailPreserved automatic inhibition effect after 1 Hz repetitive transcranial magnetic stimulation over the supplementary motor area
D'Ostilio, Kevin ULiege; CREMERS, Julien ULiege; DELVAUX, Valérie ULiege et al

Poster (2013)

Background: It is widely accepted that medial frontal regions are involved in voluntary action control. Indeed, Sumner et al. (2007) have recently suggested that one of the mechanisms through which the ... [more ▼]

Background: It is widely accepted that medial frontal regions are involved in voluntary action control. Indeed, Sumner et al. (2007) have recently suggested that one of the mechanisms through which the supplementary motor area (SMA) contributes to voluntary control is automatic and unconscious motor inhibition. In this study, they administered a visuo-motor subliminal masked prime task (Eimer & Schlaghecken, 2003) to two patients with micro-lesions of the SMA and demonstrated an absence of automatic and unconscious inhibition as evoked by masked prime stimuli. This finding has been supported by neuroimaging data (D'Ostilio et al., 2012). Here, the aim of our research was to corroborate this result by means of a “virtual lesion” approach. Methods: For this purpose, we examined the effects of 1 Hz rTMS (train of 20 min; stimulus intensity 120 % of resting motor threshold) over the SMA of ten healthy volunteers, previously localized by functional magnetic resonance imaging (fMRI), on reaction time (RT) performance in the subliminal masked prime task. The functional localizer experiment consisted of four blocks of sequential finger tapping and 15 s of rest after each block. Imaging data were analyzed with SPM 8 and then were imported into the Brainsight software version 2.1.5. With such system, we were able to navigate across the subjects’ brain. The peak voxel in the SMA for each subject (at a statistical threshold of p < 0.05 uncorrected) was used as a target point for the rTMS session. Results: The mean motor threshold was 50.9 % of maximal stimulator output (SD: ± 4.86 %). Wilcoxon tests showed a significant effect of compatibility on RTs (sham: Z = 2.7, p = 0.007; rTMS: Z = 2.8, p = 0.005) and accuracy rate (sham: Z = 2.5, p = 0.01; rTMS: Z = 2.1, p = 0.03), subjects being slower and making more errors in compatible trials (sham: 391.64 ± 52 ms, 87.3 % of accuracy; rTMS: 396.66 ± 37 ms, 86.3 % of accuracy) in comparison to incompatible trials (sham: 357.45 ± 36 ms, 92.5 % of accuracy; rTMS: 356.25 ± 28 ms, 92.7 % of accuracy), suggesting motor inhibition. However, this NCE was preserved after rTMS over the SMA (RTs: Z = 0.87, p = 0.39; accuracy rate: Z = 0.71, p = 0.47). Conclusions: We conclude that long trains of low intensity 1 Hz rTMS did not affect the modulation of RT by subliminal stimuli, suggesting that the SMA might not be mandatory for the implementation of this automatic process. The limitation of this study is relative to the neural efficacy argument because we are not sure that TMS was strong enough to disturb the redundant organizational processing in the SMA or that other regions were not able to compensate for the virtually lesioned area. [less ▲]

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See detailLocalizing and comparing weight maps generated from linear kernel machine learning models
Schrouff, Jessica ULiege; CREMERS, Julien ULiege; GARRAUX, Gaëtan ULiege 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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See detailDiscriminant BOLD Activation Patterns during Mental Imagery in Parkinson’s Disease
Schrouff, Jessica ULiege; Cremers, Julien ULiege; D'Ostilio, Kevin ULiege et al

in Proceedings of MLINI 2012 (2012, December 07)

Using machine learning based models in clinical applications has become current practice and can prove useful to provide information at the subject’s level, such as predicting an (early) diagnosis or ... [more ▼]

Using machine learning based models in clinical applications has become current practice and can prove useful to provide information at the subject’s level, such as predicting an (early) diagnosis or monitoring the evolution of a disease. However, the performance of these models depends on the choice of a biomarker to detect the presence or absence of a disease. Choosing a biomarker is not straightforward, especially in the case of Parkinson’s disease when compared to healthy subjects. In the present work, we investigated the mental imagery of gait as a biomarker of Parkinson’s disease and showed that the signal in the mesencephalic locomotor region during the mental imagery of gait at a comfortable pace can discriminate significantly between idiopathic Parkinson’s disease patients and healthy subjects. Although there is room for improvement, the results of this preliminary study are promising. [less ▲]

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See detailConstruction and validation of the Dynamic Parkinson Gait Scale (DYPAGS).
Cremers, Julien ULiege; PHAN BA, Remy ULiege; DELVAUX, Valérie ULiege et al

in Parkinsonism and Related Disorders (2012)

The dynamic evaluation of Parkinson's disease (PD)-related episodic gait disturbances in routine is challenging. Therefore, the aim of our study was to assess the reliability/validity of the Dynamic ... [more ▼]

The dynamic evaluation of Parkinson's disease (PD)-related episodic gait disturbances in routine is challenging. Therefore, the aim of our study was to assess the reliability/validity of the Dynamic Parkinson Gait Scale (DYPAGS) composed of eight relevant items for the objective quantification of PD gait features: walking forwards/backwards/with dual-task, turning to both sides, imaginary obstacle avoidance with both legs and passing through narrow spaces. The scale was validated on thirty-five patients with mild to severe parkinsonism in their habitual "on-state". A shorter 6 item-version was designed on the basis of a principal component analysis. No significant floor/ceiling effect was detected. The internal consistency was excellent. The levels of interrater agreement, precision and minimal detectable change were adequate. The criterion-related validity was demonstrated by strong correlations with the DYPAGS scores and those at the gait subscales of the Tinetti Mobility Test and MDS-UPDRS. The construct validity was assessed by moderate-strong correlations with the Freezing of Gait Questionnaire, mobility index of the PD Questionnaire (PDQ-39), disease duration and levodopa equivalent daily doses. Statistical analyses using the coefficient of determination showed that both DYPGAS versions were superior to the other instruments to identify patients with gait disturbances with poorer response to dopaminergic treatment. Full and short DYPAGS are reliable instruments for the quantification of "on" PD-related episodic gait disturbances. The full version is sensitive to detect subtle disturbances in mild parkinsonism. The shorter one is easily administered and reliably quantifies gait disturbances in moderate to severe parkinsonism. We recommend their use for research and clinical practice. [less ▲]

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See detailEffects of light deprivation on visual evoked potentials in migraine without aura.
Coppola, Gianluca; Cremers, Julien ULiege; GERARD, Pascale ULiege et al

in BMC Neurology (2011), 11

BACKGROUND: The mechanisms underlying the interictal habituation deficit of cortical visual evoked potentials (VEP) in migraine are not well understood. Abnormal long-term functional plasticity of the ... [more ▼]

BACKGROUND: The mechanisms underlying the interictal habituation deficit of cortical visual evoked potentials (VEP) in migraine are not well understood. Abnormal long-term functional plasticity of the visual cortex may play a role and it can be assessed experimentally by light deprivation (LD). METHODS: We have compared the effects of LD on VEP in migraine patients without aura between attacks (MO, n = 17) and in healthy volunteers (HV, n = 17). Six sequential blocks of 100 averaged VEP at 3.1 Hz were recorded before and after 1 hour of LD. We measured VEP P100 amplitude of the 1st block of 100 sweeps and its change over 5 sequential blocks of 100 responses. RESULTS: In HV, the consequence of LD was a reduction of 1st block VEP amplitude and of the normal habituation pattern. By contrast, in MO patients, the interictal habituation deficit was not significantly modified, although 1st block VEP amplitude, already lower than in HV before LD, further decreased after LD. CONCLUSIONS: Light deprivation is thought to decrease both excitatory and subsequent inhibitory processes in visual cortex, which is in line with our findings in healthy volunteers. The VEP results in migraine patients suggest that early excitation was adequately suppressed, but not the inhibitory mechanisms occurring during long term stimulation and habituation. Accordingly, deficient intracortical inhibition is unlikely to be a primary factor in migraine pathophysiology and the habituation deficit. [less ▲]

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