245 research outputs found
Hemispheric asymmetries in goal-directed hand movements are independent of hand preference
No full textAsymmetries in the kinematics and neural substrates of voluntary right and left eye-hand coordinated movements have been accredited to differential hemispheric specialization. An alternative explanation for between-hand movement differences could result from hand-preference related effects. To test both assumptions, an experiment was conducted with left- and right-handers performing goal-directed movements with either hand paced by a metronome. Spatiotemporal accuracy was comparable between hands, whereas hand peak velocity was reached earlier when moving with the left compared to the right hand. The underlying brain activation patterns showed that both left- and right-handers activated more areas involved in visuomotor attention and saccadic control when using their left compared to the right hand. Altogether, these results confirm a unique perceptuomotor processing specialization of the left brain/right hand system that is independent of hand preference.sponsorship: Werner Helsen and Ann Lavrysen acknowledge the KU Leuven Research Council for their support of this research project (OT/00/40). The authors also wish to thank Ir. Marc Beirinckx and Ir. Paul Meugens for providing invaluable guidance in designing the research equipment and the electronics. (KU Leuven Research Council|OT/00/40)status: Publishe
The relation between cognitive and motor dysfunction and motor imagery ability in patients with multiple sclerosis
No full textBackground: Motor imagery (MI) was recently shown to be a promising tool in neurorehabilitation. The ability to perform motor imagery, however, may be impaired in part of the patients with neurological dysfunction.
Objective: To assess the relation between cognitive and motor dysfunction and MI ability in patients with multiple sclerosis (MS).
Methods: 30 patients with MS underwent a cognitive and motor screening, as well as performed a composite test battery to assess their MI ability. This test battery consisted of a questionnaire, a hand rotation task and a test based on mental chronometry. Patients’ MI ability was compared with the MI ability of age-matched healthy controls. As well, their MI scores were compared between body sides and were correlated with their scores on tests of motor and cognitive functioning.
Results: The average accuracy and temporal organisation of MI significantly differed between MS patients and controls. Patients’ MI accuracy significantly correlated with impairments in cognitive functioning, but was independent of motor functioning. MI duration, on the other hand, was independent of cognitive performance, but differed between patients’ most and least affected side.
Conclusion: These findings are of use when considering the application of motor imagery practice in MS patients’ rehabilitation
The relative age effect in youth and elite sport: what can we learn after 20 years of research?
No full textWerner F. Helsen completed his PhD at KU Leuven in 1989. Since 2005, he is full professor at the Faculty of Movement and Rehabilitation Sciences at KU Leuven. His research and teaching involvements are in the motor control and learning field as well as in the area of training and coaching in team sports in general and football, in particular. He is promoter of 11 PhD dissertations and published over 120 publications in internationally reviewed scientific journals, including high-impact scientific journals in the fields of behavioral sciences and neurosciences, such as Psychological Bulletin (IF=6.88), NeuroImage (IF=6.13), Sports Medicine (IF=5.58). On September 2017, Google Scholar shows 6358 citations, H-index = 39, and i10 index=82. As from 1999 on, he has been appointed by FIFA and UEFA as a sports scientist and training expert for the performance training and analysis of the match officials. In this respect, he was actively involved in 5 UEFA European Championships (2000, 2004, 2008, 2012, 2016) and 3 FIFA World Cups (2002, 2006, 2010).In recent decades, our research team (among others) has identified obvious participation and attainment inequalities resulting from annual age grouping procedures across varying forms and levels of sport participation, and the relative age effects (RAEs) associated with it. Generally, youth born early in the selection year have selection and attainment advantages over their relatively younger peers. Twenty years ago, Helsen et al. (1998) observed that 37.9% of soccer players who were transferred from lower league teams to first division teams were born in the first three months of the selection year, while only 12.3% were born in the final three months. Almost a decade ago, Baker et al. (2010) observed that over 35% of players in two amateur developmental ice hockey leagues were born in the first three months of the selection year, while less than 10% were born in the final three months. Over-representation of relatively older players have been consistently observed in a variety of sports (Cobley et al., 2009; Musch & Grondin, 2001). I will discuss the (dis)advantages in selection and attainment that are considered RAEs (Wattie et al., 2008) and how they have changed (or not) over the past 20 years
Helsen, Gilis, and Weston (2006) do not err in questioning the optical error hypothesis as the only major account for explaining offside decision-making errors
No full textOudejans, Bakker, and Beek (2007) recognize several relevant aspects of offside judgements in association football in the paper by Helsen, Gilis, and Weston (2006). We agree that the existing knowledge base on offside assessment needs to be expanded for two reasons. First, from a theoretical point of view it is important to examine how assistant referees can learn to deal with the limitations of the human visual information processing system. Second, from a practical point of view it is relevant to understand better refereeing performances and to identify potential explanations for incorrect offside decisions that could impact on the final outcome of the game. Oudejans et al. (2007) believe we both misinterpreted the optical error hypothesis and that our data set was unsuited to test it. Below, we react to these comments.</p
Representations of the multi-qubit Clifford group
No full textThe q-qubit Clifford group, that is, the normalizer of the q-qubit Pauli group in U(2q), is a fundamental structure in quantum information with a wide variety of applications. We characterize all irreducible subrepresentations of the two-copy representation φ⊗2 of the Clifford group on the two-fold tensor product of the space of linear operators M2q⊗2. In the companion paper [Helsen et al., e-print arXiv:1701.04299 (2017)], we apply this result to improve the statistics of randomized benchmarking, a method for characterizing quantum systems.Accepted Author ManuscriptQuantum Information and SoftwareQuantum Internet Divisio
Facilitation of motor imagery through movement-related cueing
No full textIn the past few years, the use of motor imagery as an adjunct to other forms of training has been studied extensively. However, very little attention has been paid to how imagery could be used to greatest effect. it is well known that the provision of external cues has a beneficial effect on motor skill acquisition and performance during physical practice. Since physical execution and mental imagery share several common mechanisms, we hypothesized that motor imagery might be affected by external cues in a similar way. To examine this, we compared the motor imagery performance of three groups of 15 healthy participants who either physically performed or imagined performing a goal-directed cyclical wrist movement in the presence or the absence of visual and/or auditory external cues. As outcome measures, the participants' imagery vividness scores and eye movements were measured during all conditions. We found that visual movement-related cues improved the spatial accuracy of the participants' eye movements during imagery, while auditory cues specifically enhanced their temporal accuracy. Furthermore, both types of cues significantly improved the participants' imagery vividness. These findings indicate that subjects may imagine a movement in a better way when provided with external movement-related stimuli, which may possibly be useful with regard to the efficiency of mental practice in (clinical) training protocols. (C) 2009 Elsevier B.V. All rights reserved
External cueing improves motor imagery quality in patients with Parkinson disease
No full textBACKGROUND: Patients with Parkinson disease (PD) are often profoundly slow in their performance of physical tasks, as well as in motor imagery (MI). This may limit the implementation and potential benefits of MI practice during rehabilitation. OBJECTIVE: The authors investigated whether the quality of MI could be improved by external cueing. METHODS: Fourteen patients with PD and 14 healthy controls physically executed and visually imagined a goal-directed aiming task and a box-and-block task, both in the presence and absence of visual and auditory cues. Mental chronometry and eye movement recording allowed objective evaluation of the temporal and spatial characteristics of MI when compared with physical execution. Visual analogue scales were used to assess imagery vividness. RESULTS: The presence of visual cues significantly reduced the patients' bradykinesia during MI and increased their imagery vividness. CONCLUSIONS: Visual cueing optimizes MI quality for PD patients and is a potential tool to increase the efficacy of MI practice in PD rehabilitation.sponsorship: Elke Heremans is a research assistant and Wim Vandenberghe a senior clinical investigator at the Research Foundation Flanders (FWO). The authors also acknowledge the support of the Belgian Charcot Foundation to obtain eye movement recording equipment. (Belgian Charcot Foundation)status: Publishe
Motor Imagery Ability in Patients With Early- and Mid-Stage Parkinson Disease
No full text Background. Motor imagery has recently gained attention as a promising new rehabilitation method for patients with neurological disorders. Up to now, however, it has been unclear whether this practice method can also be successfully applied in the rehabilitation of patients with Parkinson disease (PD). Objective. This study aimed to investigate whether the motor imagery ability of patients with PD is still intact despite basal ganglia dysfunctioning. Methods. A total of 14 patients with early- and mid-stage PD (Hoehn and Yahr 1-3) and 14 healthy controls were evaluated by means of an extensive imagery ability assessment battery, consisting of 2 questionnaires, the Chaotic Motor Imagery Assessment battery, and a test based on mental chronometry. Results. PD patients performed the imagery tasks more slowly than controls, but the motor imagery vividness and accuracy of most patients were well preserved. Conclusions. These results are promising regarding the potential use of motor imagery practice in the rehabilitation of patients with PD. </jats:p
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