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Hinder M.R.,University of Tasmania | Reissig P.,University of Tasmania | Fujiyama H.,University of Tasmania | Fujiyama H.,Movement Control and Neuroplasticity Research Group
Journal of Neurophysiology | Year: 2014

Seminal work in animals indicates that learning a motor task results in long-term potentiation (LTP) in primary motor cortex (M1) and a subsequent occlusion of LTP induction (Rioult-Pedotti et al. J Neurophysiol 98: 3688-3695, 2007). Using various forms of noninvasive brain stimulation in conjunction with a motor learning paradigm, Cantarero et al. (J Neurosci 33: 12862-12869, 2013) recently provided novel evidence to support the hypothesis that retention of motor skill is contingent upon this postlearning occlusion. © 2014 the American Physiological Society.

Hoogkamer W.,Movement Control and Neuroplasticity Research Group | Hoogkamer W.,VU University Amsterdam | Hoogkamer W.,Catholic University of Leuven
Perceptual and Motor Skills | Year: 2014

In a recent work on locomotor symmetry while walking on a splitbelt treadmill, Lauzière and co-workers determined the perception threshold of gait symmetry in a sample of healthy elderly. In addition, they aimed to determine which particular gait parameters affect the symmetry of the perception threshold. Although only temporal and kinetic gait parameters were measured (and no kinematics), it was suggested that stance time symmetry is an important criterion that participants use to identify the threshold. Here it is argued that several other gait parameters could qualify equally well as main criteria used to identify the threshold and that these parameters should be taken into account in future studies. © Perceptual & Motor Skills 2014.

Davare M.,Catholic University of Leuven | Davare M.,University College London | Davare M.,Movement Control and Neuroplasticity Research Group | Zenon A.,Catholic University of Leuven | And 2 more authors.
Frontiers in Human Neuroscience | Year: 2015

To reach for an object, we must convert its spatial location into an appropriate motor command, merging movement direction and amplitude. In humans, it has been suggested that this visuo-motor transformation occurs in a dorsomedial parieto-frontal pathway, although the causal contribution of the areas constituting the “reaching circuit” remains unknown. Here we used transcranial magnetic stimulation (TMS) in healthy volunteers to disrupt the function of either the medial intraparietal area (mIPS) or dorsal premotor cortex (PMd), in each hemisphere. The task consisted in performing step-tracking movements with the right wrist towards targets located in different directions and eccentricities; targets were either visible for the whole trial (Target-ON) or flashed for 200 ms (Target-OFF). Left and right mIPS disruption led to errors in the initial direction of movements performed towards contralateral targets. These errors were corrected online in the Target-ON condition but when the target was flashed for 200 ms, mIPS TMS manifested as a larger endpoint spreading. In contrast, left PMd virtual lesions led to higher acceleration and velocity peaks—two parameters typically used to probe the planned movement amplitude—irrespective of the target position, hemifield and presentation condition; in the Target-OFF condition, left PMd TMS induced overshooting and increased the endpoint dispersion along the axis of the target direction. These results indicate that left PMd intervenes in coding amplitude during movement preparation. The critical TMS timings leading to errors in direction and amplitude were different, namely 160–100 ms before movement onset for mIPS and 100–40 ms for left PMd. TMS applied over right PMd had no significant effect. These results demonstrate that, during motor preparation, direction and amplitude of goal-directed movements are processed by different cortical areas, at distinct timings, and according to a specific hemispheric organization. © 2015 Davare, Zénon, Desmurget and Olivier.

Jansen K.,Human Movement Biomechanics Research Group | De Groote F.,Catholic University of Leuven | Duysens J.,Catholic University of Leuven | Duysens J.,Movement Control and Neuroplasticity Research Group | Jonkers I.,Human Movement Biomechanics Research Group
Gait and Posture | Year: 2014

Maintaining mediolateral (ML) balance is very important to prevent falling during walking, especially at very slow speeds. The effect of walking speed on support and propulsion of the center of mass (COM) has been focus of previous studies. However, the influence of speed on ML COM control and the associated coupling with sagittal plane control remains unclear. Simulations of walking at very slow and normal speeds were generated for twelve healthy subjects. Our results show that gluteus medius (GMED) contributions to ML stability decrease, while its contributions to sagittal plane accelerations increase during very slow compared to normal walking. Simultaneously the destabilizing influence of gravity increases in ML direction at a very slow walking speed. This emphasizes the need for a tight balance between gravity and gluteus medius action to ensure ML stability. When walking speed increases, GMED has a unique role in controlling ML acceleration and therefore stabilizing ML COM excursion. Contributions of other muscles decrease in all directions during very slow speed. Increased contributions of these muscles are therefore required to provide for both stability and propulsion when walking speed increases. © 2013 Elsevier B.V.

de Beukelaar T.T.,Movement Control and Neuroplasticity Research Group | Woolley D.G.,Movement Control and Neuroplasticity Research Group | Wenderoth N.,Movement Control and Neuroplasticity Research Group | Wenderoth N.,ETH Zurich
Cortex | Year: 2014

When a stable memory is reactivated it becomes transiently labile and requires restabilization, a process known as reconsolidation. Animal studies have convincingly demonstrated that during reconsolidation memories are modifiable and can be erased when reactivation is followed by an interfering intervention. Few studies have been conducted in humans, however, and results are inconsistent regarding the extent to which a memory can be degraded. We used a motor sequence learning paradigm to show that the length of reactivation constitutes a crucial boundary condition determining whether human motor memories can be degraded. In our first experiment, we found that a short reactivation (less than 60sec) renders the memory labile and susceptible to degradation through interference, while a longer reactivation does not. In our second experiment, we reproduce these results and show a significant linear relationship between the length of memory reactivation and the detrimental effect of the interfering task performed afterwards, i.e., the longer the reactivation, the smaller the memory loss due to interference. Our data suggest that reactivation via motor execution activates a time-dependent process that initially destabilizes the memory, which is then followed by restabilization during further practice. © 2014 Elsevier Ltd.

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