Publications by authors named "Raf Meesen"

36 Publications

Unravelling ipsilateral interactions between left dorsal premotor and primary motor cortex: a proof of concept study.

Neuroscience 2021 May 7. Epub 2021 May 7.

Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium; Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium. Electronic address:

Few studies have identified the intrahemispheric functional connectivity between the ipsilateral dorsal premotor cortex (PMd) and the primary motor hand area (M1) due to technical limitations. In this proof-of-concept study, a novel neuronavigated dsTMS set-up was employed, combining stimulation over left PMd and left M1 using the edge of a butterfly coil and a small cooled-coil. This arrangement was warranted because coil (over)heating and inter coil distance are limiting factors when investigating connectivity between stimulation targets in close proximity and over a longer duration. The proposed set-up was designed to deal with these limitations. Specifically, the effect of four dual-site transcranial magnetic stimulation (dsTMS) protocols on twenty-eight right-handed participants (12 males) was evaluated. These protocols differed in stimulus order, interstimulus interval and current direction induced in PMd. A structural scan with electric (E-)field modeling was obtained from seven participants prior to dsTMS, demonstrating that PMd and M1 were effectively stimulated. Results indicate that one protocol, in which a latero-medial current was induced in PMd 2.8 ms prior to stimulation over M1, induced a sex-mediated effect. In males, significant inhibition of motor-evoked potentials was identified, whereas females demonstrated a facilitatory effect that did not survive correction for multiple comparisons. E-field simulations revealed that the E-field induced by the coil targeting PMd was maximal in PMd, with weaker E-field strengths extending to regions beyond PMd. Summarizing, the current dsTMS set-up enabled stimulating at an inter-target distance of 35 mm without any indications of coil-overheating.
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http://dx.doi.org/10.1016/j.neuroscience.2021.04.033DOI Listing
May 2021

Rhythmic interlimb coordination of the lower limbs in multiple sclerosis during auditory pacing to three different frequencies.

Gait Posture 2021 May 5;86:334-340. Epub 2021 Apr 5.

REVAL Rehabilitation Research Center, Faculty of Rehabilitation Sciences, Hasselt University, Hasselt, Belgium; UMSC Pelt-Hasselt, Belgium. Electronic address:

Background: Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system with heterogeneous symptoms. Persons with MS (PwMS) show reduced walking capacity with changes in their gait pattern. It is unknown to which extent coordination deficits are present in PwMS, which can be measured by seated lower leg interlimb coordination tasks, and to which extent they are related to motor and cognitive function.

Research Question: How is the control of interlimb coordination of the lower limbs characterized in PwMS compared to healthy controls (HC) during a seated rhythmical coordination task and what is the relationship between interlimb coordination, motor or cognitive function?

Methods: Rhythmical interlimb coordination was assessed during a single session in 38 PwMS and 13 HC, using a seated rhythmical coordination task, comprising of antiphase flexion-extension of the lower limbs, to metronomes at 0.75 Hz, 1.00 Hz, 1.50 Hz. Outcomes were phase coordination index (PCI), movement amplitude and movement frequency. Correlations between interlimb coordination, motor, and cognitive function were examined.

Results: PwMS showed impaired walking capacity but preserved cognitive function. Mixed model analysis revealed a significant effect of group and metronome frequency for PCI, attenuated by the variability in generating knee (antiphase flexion-extension) movements. Movement amplitude was highest at metronome frequency 1.00 Hz. In PwMS significant correlations were found between PCI and cognitive function when performing the task at metronome frequencies 0.75 Hz and 1.50 Hz, as well as motor function at 1.50 Hz.

Significance: PwMS had a higher variability in interlimb coordination compared to HC. The most stable interlimb antiphase coordination mode was performed at 1.00 Hz. Significant correlations support the existence of a relationship between information processing speed, as well as walking impairment, with interlimb coordination. While cognitive and motor control are always needed for interlimb coordination movements, associations are strongest in the deviant higher and lower metronome rhythms.
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http://dx.doi.org/10.1016/j.gaitpost.2021.04.001DOI Listing
May 2021

Dissociating the causal role of left and right dorsal premotor cortices in planning and executing bimanual movements - A neuro-navigated rTMS study.

Brain Stimul 2021 Mar-Apr;14(2):423-434. Epub 2021 Feb 20.

Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium; Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Leuven, Belgium.

Background: The dorsal premotor cortex (PMd) is a key region in bimanual coordination. However, causal evidence linking PMd functionality during motor planning and execution to movement quality is lacking.

Objective: We investigated how left (PMd) and right PMd (PMd) are causally involved in planning and executing bimanual movements, using short-train repetitive transcranial magnetic stimulation (rTMS). Additionally, we explored to what extent the observed rTMS-induced modulation of performance could be explained by rTMS-induced modulation of PMd-M1 interhemispheric interactions (IHI).

Methods: Twenty healthy adults (mean age ± SD = 22.85 ± 3.73 years) participated in two sessions, in which either PMd or PMd was targeted with rTMS (10 Hz) in a pseudo-randomized design. PMd functionality was transiently modulated during the planning or execution of a complex bimanual task, whereby the participant was asked to track a moving dot by controlling two dials. The effect of rTMS on several performance measures was investigated. Concurrently, rTMS-induced modulation of PMd-M1 IHI was measured using a dual-coil paradigm, and associated with the rTMS-induced performance modulation.

Results: rTMS over PMd during planning increased bilateral hand movement speed (p = 0.03), thereby improving movement accuracy (p = 0.02). In contrast, rTMS over PMd during both planning and execution induced deterioration of movement stability (p = 0.04). rTMS-induced modulation of PMd-M1 IHI during planning did not predict rTMS-induced performance modulation.

Conclusion: The current findings support the growing evidence on PMd dominance during motor planning, as PMd was crucially involved in planning the speed of each hand, subserving bimanual coordination accuracy. Moreover, the current results suggest that PMd fulfills a role in continuous adjustment processes of movement.
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http://dx.doi.org/10.1016/j.brs.2021.02.006DOI Listing
February 2021

Clinical manifestation and perceived symptoms of walking-related performance fatigability in persons with multiple sclerosis.

Int J Rehabil Res 2021 06;44(2):118-125

REVAL Rehabilitation Research Center, Faculty of Rehabilitation Sciences, Hasselt University, Hasselt, Belgium.

Fatigue and walking difficulties are common impairments and activity limitations in persons with multiple sclerosis (PwMS). Walking fatigability (WF) can be measured by a Distance Walked Index and is defined as a decline in walking distance of 10% or more during the six-minute walking test (6MWT). However, the clinical manifestation and perceived symptoms related to fatigability are still not well documented. Forty-nine PwMS [Expanded Disability Status Scale (EDSS) ≤6] and 28 healthy controls (HC) performed a 6MWT. The perceived severity of 11 common symptoms was rated on a visual analogue scale of 0-10 before, immediately after, and 10, 20 and 30 minutes after the 6MWT by means of the symptom inventory. Short motor impairment screening tests at baseline together with other descriptive measures were performed. Twenty pwMS were categorized in the WF group and were more disabled (EDSS: 4.16 ± 1.41) than the non-walking fatigability group (n = 29, EDSS: 2.62 ± 1.94). PwMS showed exacerbations of several perceived symptoms in MS, where most symptoms returned to baseline within 10 minutes after the walking test. The WF group showed significantly more muscle weakness and gait impairment, together with balance problems, and experienced an increase in spasticity, pain and dizziness after 6MWT. Our findings showed that perceived severity of symptoms are higher in pwMS presenting WF, and increase temporally after the 6MWT. Future research with quantitative measurement during and after walking is recommended.
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http://dx.doi.org/10.1097/MRR.0000000000000457DOI Listing
June 2021

Transcranial direct current stimulation and attention skills in burnout patients: a randomized blinded sham-controlled pilot study.

F1000Res 2020 14;9:116. Epub 2020 Feb 14.

Service de Neurologie, CHU-Charleroi, Charleroi, Henegouwen, 6041, Belgium.

Burnout is characterized by deficiencies in attention and several components of the working memory. It has been shown that cognitive behavioral therapy can have a positive effect on burnout and depressive symptoms, however, the lingering effects of impaired attention and executive functions are the most frustrating. We hypothesized that anodal transcranial direct current stimulation (atDCS) over the left dorsolateral prefrontal cortex (DLPFC) can improve the executive control of attention and possibly several other components of working memory in patients with burnout. This was a randomized double-blind sham-controlled pilot study with two groups. Patients with burnout received three weeks of daily sessions (15 sessions in total) of atDCS or sham stimulation in addition to three weekly sessions of standard behavioral therapy. The primary outcome measure was attention and the central executive of the working memory. Secondary, the effect of atDCS was measured on other components of working memory, on burnout and depression scores, and on quality of life (QoL). We enrolled and randomly assigned 16 patients to a sham or real stimulation group, 15 (7 sham, 8 real) were included in the analysis. atDCS had a significant impact on attention. Post-hoc comparisons also revealed a trend towards more improvement after real tDCS for inhibition and shifting, updating and control, and encoding. Both groups improved on burnout and depression scores. These data provide preliminary evidence for the value of atDCS over the left DLPFC in rehabilitating attention deficits, and possibly also central executive and encoding deficits, in burnout. However, the current study has some limitations, including the sample size and heterogeneous patient population. More elaborate studies are needed to elucidate the specific impact of atDCS over the left DLPFC on burnout. ISRCTN.com ( ISRCTN94275121) 17/11/19.
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http://dx.doi.org/10.12688/f1000research.21831.2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7737710PMC
February 2021

Frailty is highly prevalent in specific cardiovascular diseases and females, but significantly worsens prognosis in all affected patients: A systematic review.

Ageing Res Rev 2021 03 14;66:101233. Epub 2020 Dec 14.

REVAL, Rehabilitation Research Center, Faculty of Rehabilitation Sciences, Hasselt University, Diepenbeek, Belgium; Heart Centre Hasselt, Jessa Hospital, Hasselt, Belgium; BIOMED, Biomedical Research Center, Hasselt University, Diepenbeek, Belgium.

Cardiologists are more often confronted with older (>60 years) cardiovascular disease (CVD) patients. These patients have particular needs in clinical care because, for example, of frailty. However, it remains to be established what is the prevalence of frailty in different CVD's and how it relates to mortality. In this systematic review studies were included if they: (i) examined subjects (men and women) aged ≥60 years who suffered from any CVD with or without cardiac surgery, (ii.) examined the presence of frailty with a well-defined frailty tool and (iii.) reported prevalence rates of frailty. From thirty studies comprising 96.841 participants, it is found that 1. Frailty is highly common in older patients with CVD (in particular in females (approximately 1.6 times more than in males), in heart failure (up to 80 % of patients) and aortic valve disease (up to 74 % of patients)), and 2. Frailty is related to a 2.5-3.5-fold elevated mortality risk, even in patients with less severe CVD (e.g. percutaneous coronary intervention). Moreover, there is a lack of consistency on how to assess frailty as up to 20 different tools/assessment batteries are currently used. It is concluded that frailty should be assessed in all older CVD patients in a uniform manner to enhance clinical care and outcomes.
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http://dx.doi.org/10.1016/j.arr.2020.101233DOI Listing
March 2021

Age-related differences of motor cortex plasticity in adults: A transcranial direct current stimulation study.

Brain Stimul 2020 Nov - Dec;13(6):1588-1599. Epub 2020 Sep 17.

Department of Psychology and Neurosciences, Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany; Department of Neurology, University Medical Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany. Electronic address:

Background: Cognitive, and motor performance are reduced in aging, especially with respect to acquisition of new knowledge, which is associated with a neural plasticity decline. Animal models show a reduction of long-term potentiation, but not long-term depression, in higher age. Findings in humans are more heterogeneous, with some studies showing respective deficits, but others not, or mixed results, for plasticity induced by non-invasive brain stimulation. One reason for these heterogeneous results might be the inclusion of different age ranges in these studies. In addition, a systematic detailed comparison of the age-dependency of neural plasticity in humans is lacking so far.

Objective: We aimed to explore age-dependent plasticity alterations in adults systematically by discerning between younger and older participants in our study.

Methods: We recruited three different age groups (Young: 18-30, Pre-Elderly: 50-65, and Elderly: 66-80 years). Anodal, cathodal, or sham transcranial direct current stimulation (tDCS) was applied over the primary motor cortex with 1 mA for 15 min to induce neuroplasticity. Cortical excitability was monitored by single-pulse transcranial magnetic stimulation as an index of plasticity.

Results: For anodal tDCS, the results show a significant excitability enhancement, as compared to sham stimulation, for both, Young and the Pre-Elderly groups, while no LTP-like plasticity was obtained in the Elderly group by the applied stimulation protocol. Cathodal tDCS induced significant excitability-diminishing plasticity in all age groups.

Conclusion: Our study provides further insight in age-related differences of plasticity in healthy humans, which are similar to those obtained in animal models. The decline of LTP-like plasticity in higher age could contribute to cognitive deficits observed in aging.
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http://dx.doi.org/10.1016/j.brs.2020.09.004DOI Listing
April 2021

Induced Suppression of the Left Dorsolateral Prefrontal Cortex Favorably Changes Interhemispheric Communication During Bimanual Coordination in Older Adults-A Neuronavigated rTMS Study.

Front Aging Neurosci 2020 26;12:149. Epub 2020 May 26.

Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium.

Recent transcranial magnetic stimulation (TMS) research indicated that the ability of the dorsolateral prefrontal cortex (DLPFC) to disinhibit the contralateral primary motor cortex (M1) during motor preparation is an important predictor for bimanual motor performance in both young and older healthy adults. However, this DLPFC-M1 disinhibition is reduced in older adults. Here, we transiently suppressed left DLPFC using repetitive TMS (rTMS) during a cyclical bimanual task and investigated the effect of left DLPFC suppression: (1) on the projection from left DLPFC to the contralateral M1; and (2) on motor performance in 21 young (mean age ± SD = 21.57 ± 1.83) and 20 older (mean age ± SD = 69.05 ± 4.48) healthy adults. As predicted, without rTMS, older adults showed compromised DLPFC-M1 disinhibition as compared to younger adults and less preparatory DLPFC-M1 disinhibition was related to less accurate performance, irrespective of age. Notably, rTMS-induced DLPFC suppression restored DLPFC-M1 disinhibition in older adults and improved performance accuracy right after the local suppression in both age groups. However, the rTMS-induced gain in disinhibition was not correlated with the gain in performance. In sum, this novel rTMS approach advanced our mechanistic understanding of how left DLPFC regulates right M1 and allowed us to establish the causal role of left DLPFC in bimanual coordination.
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http://dx.doi.org/10.3389/fnagi.2020.00149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272719PMC
May 2020

Current intensity- and polarity-specific online and aftereffects of transcranial direct current stimulation: An fMRI study.

Hum Brain Mapp 2020 04 20;41(6):1644-1666. Epub 2019 Dec 20.

Department Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.

Transcranial direct current stimulation (tDCS) induces polarity- and dose-dependent neuroplastic aftereffects on cortical excitability and cortical activity, as demonstrated by transcranial magnetic stimulation (TMS) and functional imaging (fMRI) studies. However, lacking systematic comparative studies between stimulation-induced changes in cortical excitability obtained from TMS, and cortical neurovascular activity obtained from fMRI, prevent the extrapolation of respective physiological and mechanistic bases. We investigated polarity- and intensity-dependent effects of tDCS on cerebral blood flow (CBF) using resting-state arterial spin labeling (ASL-MRI), and compared the respective changes to TMS-induced cortical excitability (amplitudes of motor evoked potentials, MEP) in separate sessions within the same subjects (n = 29). Fifteen minutes of sham, 0.5, 1.0, 1.5, and 2.0-mA anodal or cathodal tDCS was applied over the left primary motor cortex (M1) in a randomized repeated-measure design. Time-course changes were measured before, during and intermittently up to 120-min after stimulation. ROI analyses indicated linear intensity- and polarity-dependent tDCS after-effects: all anodal-M1 intensities increased CBF under the M1 electrode, with 2.0-mA increasing CBF the greatest (15.3%) compared to sham, while all cathodal-M1 intensities decreased left M1 CBF from baseline, with 2.0-mA decreasing the greatest (-9.3%) from sham after 120-min. The spatial distribution of perfusion changes correlated with the predicted electric field, as simulated with finite element modeling. Moreover, tDCS-induced excitability changes correlated more strongly with perfusion changes in the left sensorimotor region compared to the targeted hand-knob region. Our findings reveal lasting tDCS-induced alterations in cerebral perfusion, which are dose-dependent with tDCS parameters, but only partially account for excitability changes.
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http://dx.doi.org/10.1002/hbm.24901DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7267945PMC
April 2020

tDCS-Enhanced Consolidation of Writing Skills and Its Associations With Cortical Excitability in Parkinson Disease: A Pilot Study.

Neurorehabil Neural Repair 2019 12 18;33(12):1050-1060. Epub 2019 Nov 18.

KU Leuven, Leuven, Belgium.

. Learning processes of writing skills involve the re-engagement of previously established motor programs affected by Parkinson disease (PD). To counteract the known problems with consolidation in PD, transcranial direct current stimulation (tDCS) could be imperative to achieve a lasting regeneration of habitual motor skills. . To examine tDCS-enhanced learning of writing and explore alterations in cortical excitability after stimulation in PD compared with healthy controls (HCs). . Ten patients and 10 HCs received 2 training sessions combined with 20 minutes of 1-mA anodal tDCS or sham on the left primary motor cortex in a randomized crossover design. Writing skills on a tablet and paper were assessed at baseline, after training, and after 1 week of follow-up. Before and immediately after the intervention, cortical excitability and inhibition were measured during rest and activity. . Writing amplitude and velocity improved when practice was tDCS supplemented compared with sham in PD. Benefits were sustained at retention for trained and untrained tasks on the tablet as well as for writing on paper. No improvements were found for HCs. Reduced resting motor thresholds after tDCS indicated tDCS-enhanced cortical excitability. Additionally, increments in motor-evoked potential amplitudes correlated with improved writing in PD, whereas HCs showed the opposite pattern. . Our results endorse the usefulness of tDCS-boosted learning in PD, at least when applied to improving writing capacity. Although further confirmatory studies are needed, these novel findings are striking because tDCS-mediated consolidation was found for learning a motor task directly affected by PD.
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http://dx.doi.org/10.1177/1545968319887684DOI Listing
December 2019

Non-pulsed Sinusoidal Electromagnetic Field Rescues Animals From Severe Ischemic Stroke via NO Activation.

Front Neurosci 2019 19;13:561. Epub 2019 Jun 19.

Faculty of Medicine and Life Sciences, BIOMED, UHasselt - Hasselt University, Diepenbeek, Belgium.

Despite the high prevalence and devastating outcome, only a few treatment options for cerebral ischemic stroke exist. Based on the nitric oxide (NO)-stimulating capacity of Non-pulsed Sinusoidal Electromagnetic Field (NP-SEMF) and the possible neuroprotective role of NO in ischemic stroke, we hypothesized that NP-SEMF is able to enhance survival and neurological outcome in a rat model of cerebral ischemia. The animals, in which ischemic injury was induced by occlusion of both common carotid arteries, received 20 min of NP-SEMF of either 10 or 60 Hz daily for 4 days. NP-SEMF dramatically increased survival, reduced the size of the infarcted brain area and significantly improved the neurological score of the surviving rats. Corresponding to previous reports, NP-SEMF was able to induce NO production . The importance of NO as a key signaling molecule was highlighted by inhibition of the NP-SEMF beneficial effects in the rat stroke model after blocking NO synthase (NOS). Our results indicate for the first time that NP-SEMF exposure (13.5 mT at 60 and 10 Hz) improves the survival and neurological outcome of rats subjected to cerebral ischemia and that this effect is mediated by NO, underlining the great therapeutic potential of NP-SEMF as a therapy for ischemic stroke.
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http://dx.doi.org/10.3389/fnins.2019.00561DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6593085PMC
June 2019

The Impact of Different Types of Exercise Training on Peripheral Blood Brain-Derived Neurotrophic Factor Concentrations in Older Adults: A Meta-Analysis.

Sports Med 2019 Oct;49(10):1529-1546

Faculty of Rehabilitation Sciences, REVAL-Rehabilitation Research Center, Hasselt University, Agoralaan, Building A, 3590, Diepenbeek, Belgium.

Background: As the prevalence of neurodegenerative diseases (such as dementia) continues to increase due to population aging, it is mandatory to understand the role of exercise for maintaining/improving brain health.

Objectives: To analyse the impact of aerobic, strength and combined aerobic/strength exercise training on peripheral brain-derived neurotrophic factor (BDNF) concentrations in older adults (minimum age 60 years).

Methods: This meta-analysis adhered to PRISMA guidelines. Inclusion criteria were: (i) studies with subjects aged ≥ 60 years, (ii) completing a single exercise bout or an exercise programme, with (iii) measurements of blood BDNF in the periphery; (iv) with comparison between (a) an intervention and control group or (b) two intervention groups, or (c) pre- and post-measurements of an exercise intervention without control group. Studies with specific interest in known chronic co-morbidities or brain diseases affecting the peripheral and/or central nervous system, except for dementia, were excluded.

Results: In general, peripheral blood BDNF concentrations increased significantly after a single aerobic/strength exercise bout (Z = 2.21, P = 0.03) as well as after an exercise programme (Z = 4.72, P < 0.001). However, when comparing the different types of exercise within these programmes, the increase in the peripheral BDNF concentrations was significant after strength training (Z = 2.94, P = 0.003) and combined aerobic/strength training (Z = 3.03, P = 0.002) but not after (low-to-moderate intense) aerobic exercise training (Z = 0.82, P = 0.41).

Conclusions: Based on current evidence, to increase the peripheral blood BDNF concentrations in older adults, strength training and combined aerobic/strength training is effective. More studies are needed to examine the impact of aerobic exercise training.
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http://dx.doi.org/10.1007/s40279-019-01148-zDOI Listing
October 2019

Force decline after low and high intensity contractions in persons with multiple sclerosis.

Clin Neurophysiol 2019 03 27;130(3):359-367. Epub 2018 Dec 27.

Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. Electronic address:

Objective: Force decline during strong contractions is dominated by changes in the periphery whereas during weaker contraction changes in voluntary activation become more important. We compared force decline and contributing factors in persons with multiple sclerosis (PwMS) during low and high intensity contractions.

Methods: Index finger abduction force, force evoked by electrical stimulation of the ulnar nerve at rest (RTw), and during MVCs were investigated in 19 PwMS and 19 controls. Participants performed contractions in sets of six contractions (7 s-on, 3 s-off) at 25% or 80% MVC. After each set, a 5 s-MVC was performed with superimposed nerve stimulation followed by RTw. Contractions were repeated until MVC dropped below 80% of initial MVC.

Results: Low compared to high intensity contractions caused a greater decline in voluntary activation and a smaller decline in RTw. Compared to controls, PwMS accomplished equal sets of contractions but showed a smaller decline in RTw. Female PwMS showed poorer voluntary activation. The number of low intensity contractions was associated with sense of fatigue in PwMS.

Conclusion: Although, no difference in fatigability was observed, the mechanism contributing to force decline differed between PwMS and controls during submaximal contractions.

Significance: During weak contractions, fatigue and fatigability are associated in PwMS.
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http://dx.doi.org/10.1016/j.clinph.2018.11.027DOI Listing
March 2019

Does transcranial direct current stimulation during writing alleviate upper limb freezing in people with Parkinson's disease? A pilot study.

Hum Mov Sci 2019 Jun 28;65. Epub 2018 Feb 28.

Neuromotor Rehabilitation Research Group, Department of Rehabilitation Sciences, KU Leuven, Tervuursevest 101, Leuven, Belgium. Electronic address:

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) can boost motor performance in Parkinson's disease (PD) when it is applied at rest. However, the potential supplementary therapeutic effect of the concurrent application of tDCS during the training of motor tasks is largely unknown. The present study examined the effects of tDCS on upper limb motor blocks during a freezing-provoking writing task (the funnel task) requiring up- and down-stroke movements at alternating amplitudes. Ten PD patients and 10 age-matched controls underwent two sessions of writing combined with 20 min of anodal or sham tDCS on the left M1 in a randomized cross-over design. The primary outcome was the number of upper limb freezing episodes during five trials of the funnel task on a touch-sensitive tablet. PD patients showed a significant reduction in freezing episodes during tDCS compared to sham. No effects of tDCS were found for the amplitude, variability and speed of the strokes outside the freezing episodes. However, patients who reported freezing episodes in daily life (N = 6) showed a beneficial effect of tDCS on stroke characteristics. These results indicate a subgroup-dependent variability in response to non-invasive brain stimulation applied during the performance of motor tasks in PD. This warrants future studies to examine tDCS as an adjuvant tool for training programs aimed to reduce motor deficits related to freezing.
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http://dx.doi.org/10.1016/j.humov.2018.02.012DOI Listing
June 2019

GABA levels and measures of intracortical and interhemispheric excitability in healthy young and older adults: an MRS-TMS study.

Neurobiol Aging 2018 05 6;65:168-177. Epub 2018 Feb 6.

Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Leuven, Belgium; Rehabilitation Research Centre, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium. Electronic address:

Edited magnetic resonance spectroscopy (MRS) and transcranial magnetic stimulation (TMS) have often been used to study the integrity of the GABAergic neurotransmission system in healthy aging. To investigate whether the measurement outcomes obtained with these 2 techniques are associated with each other in older human adults, gamma-aminobutyric acid (GABA) levels in the left sensorimotor cortex were assessed with edited MRS in 28 older (63-74 years) and 28 young adults (19-34 years). TMS at rest was then used to measure intracortical inhibition (short-interval intracortical inhibition/long-interval intracortical inhibition), intracortical facilitation, interhemispheric inhibition from left to right primary motor cortex (M1) and recruitment curves of left and right M1. Our observations showed that short-interval intracortical inhibition and long-interval intracortical inhibition in the left M1 were reduced in older adults, while GABA levels did not significantly differ between age groups. Furthermore, MRS-assessed GABA within left sensorimotor cortex was not correlated with TMS-assessed cortical excitability or inhibition. These observations suggest that healthy aging gives rise to altered inhibition at the postsynaptic receptor level, which does not seem to be associated with MRS-assessed GABA+ levels.
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http://dx.doi.org/10.1016/j.neurobiolaging.2018.01.023DOI Listing
May 2018

Cerebellar gray matter explains bimanual coordination performance in children and older adults.

Neurobiol Aging 2018 05 2;65:109-120. Epub 2018 Feb 2.

KU Leuven, Department of Movement Sciences, Movement Control and Neuroplasticity Research Group, Leuven, Belgium; KU Leuven, Leuven Research Institute for Neuroscience & Disease (LIND), Leuven, Belgium.

The cerebellum appears to undergo late maturation in children and early decline at older age. Whether these age-related changes affect bimanual coordination performance remains unclear at best. Here, we identified the ages at which bimanual coordination performance stops improving and starts declining. In an independent cohort, we defined brain regions of interest involved in bimanual coordination using functional magnetic resonance imaging. We used these regions of interest to investigate the extent to which the gray matter of cerebellar and other brain regions explains bimanual coordination performance from 10- to 80-year-olds. Results showed that bimanual coordination performance starts declining from the age of 40 years. In participants aged 10-20 years, cerebellar lobule VI was the only significant brain predictor of bimanual coordination performance. In participants aged 60-80 years, this cerebellar region, together with the primary sensorimotor cortex, formed a group of strongest predictors. These results from 2 independent samples (10-20 and 60-80 years) suggest that cerebellar lobule VI is critical for the development and preservation of bimanual coordination skills in children and older adults, respectively. In addition, post hoc analyses suggested that the primary motor cortex mediated the adverse effect of age on bimanual coordination performance in older adults.
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http://dx.doi.org/10.1016/j.neurobiolaging.2018.01.016DOI Listing
May 2018

Preserved imitation in contrast to limited free application of comfortable hand actions in intellectually able young adults with an autism spectrum disorder.

Autism 2018 08 22;22(6):645-653. Epub 2017 Jun 22.

1 Faculty of Medicine and Life Sciences, Hasselt University, Belgium.

Imitation problems are commonly reported in children with an autism spectrum disorder. However, it has not yet been determined whether imitation problems persist into young adulthood. In this study, we investigated imitation skills of 20 intellectually able young adults with autism spectrum disorder relative to 19 age-matched neurotypical adults. For this purpose, we used a bar-transport task, which evokes the application of the end-state comfort principle. Specifically, we examined whether young adults with autism spectrum disorder imitated the means-end structure of a demonstrator's bar-transport action with and without application of the end-state comfort principle (imitation task). In addition, we examined whether participants spontaneously applied the end-state comfort principle during a similar bar-transport task (free execution task). Results revealed that young adults with autism spectrum disorder imitated the means-end structure of observed actions to the same degree as neurotypical adults ( p = 0.428). In contrast, they applied the end-state comfort principle less often during free executed actions ( p = 0.035). Moreover, during these actions, they were slower to place the bar into the penholder ( p = 0.023), which contributed to the reduced efficiency of their performance. Findings suggest that imitation abilities of young adults with autism spectrum disorder are preserved and that observing others' actions might promote more efficient action planning in this population.
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http://dx.doi.org/10.1177/1362361317698454DOI Listing
August 2018

Observing back pain provoking lifting actions modulates corticomotor excitability of the observer's primary motor cortex.

Neuropsychologia 2017 Jul 3;101:1-9. Epub 2017 May 3.

ETH Zurich, Department of Health Sciences and Technology, Neural Control of Movement Lab, Winterthurerstrasse 190, 8057 Zurich, Switzerland; KU Leuven, Departement of Kinesiology, Movement Control & Neuroplasticity Research Group, Tervuursevest 101, 3001 Leuven, Belgium; Neuroscience Center Zurich, University of Zurich, Federal Institute of Technology Zurich, University and Balgrist Hospital Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. Electronic address:

Observing another person experiencing exogenously inflicted pain (e.g. by a sharp object penetrating a finger) modulates the excitability of the observer' primary motor cortex (M1). By contrast, far less is known about the response to endogenously evoked pain such as sudden back pain provoked by lifting a heavy object. Here, participants (n=26) observed the lifting of a heavy object. During this action the actor (1) flexed and extended the legs (LEG), (2) flexed and extended the back (BACK) or (3) flexed and extended the back which caused visible pain (BACKPAIN). Corticomotor excitability was measured by applying a single transcranial magnetic stimulation pulse to the M1 representation of the muscle erector spinae and participants scored their perception of the actor's pain on the numeric pain rating scale (NPRS). The participants scored vicarious pain as highest during the BACKPAIN condition and lowest during the LEG condition. MEP size was significantly lower for the LEG than the BACK and BACKPAIN condition. Although we found no statistical difference in the motor-evoked potential (MEP) size between the conditions BACK and BACKPAIN, there was a significant correlation between the difference in NPRS scores between the conditions BACKPAIN and BACK and the difference in MEP size between these conditions. Participants who believed the vicarious pain to be much stronger in the BACKPAIN than in the BACK condition also exhibited higher MEPs for the BACKPAIN than the BACK condition. Our results indicate that observing how others lift heavy objects facilitates motor representations of back muscles in the observer. Modulation occurs in a movement-specific manner and is additionally modulated by the extent to which the participants perceived the actor's pain. Our findings suggest that movement observation might be a promising paradigm to study the brain's response to back pain.
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http://dx.doi.org/10.1016/j.neuropsychologia.2017.05.003DOI Listing
July 2017

tDCS over left M1 or DLPFC does not improve learning of a bimanual coordination task.

Sci Rep 2016 10 25;6:35739. Epub 2016 Oct 25.

KU Leuven, Department of Kinesiology, Movement Control and Neuroplasticity Research Group, 3001 Leuven, Belgium.

Previously, transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has resulted in improved performance in simple motor tasks. For a complex bimanual movement, studies using functional magnetic resonance imaging and transcranial magnetic stimulation indicated the involvement of the left dorsolateral prefrontal cortex (DLPFC) as well as left M1. Here we investigated the relative effect of up-regulating the cortical function in left DLPFC and left M1 with tDCS. Participants practised a complex bimanual task over four days while receiving either of five stimulation protocols: anodal tDCS applied over M1, anodal tDCS over DLPFC, sham tDCS over M1, sham tDCS over DLPFC, or no stimulation. Performance was measured at the start and end of each training day to make a distinction between acquisition and consolidation. Although task performance improved over days, no significant difference between stimulation protocols was observed, suggesting that anodal tDCS had little effect on learning the bimanual task regardless of the stimulation sites and learning phase (acquisition or consolidation). Interestingly, cognitive performance as well as corticomotor excitability did not change following stimulation. Accordingly, we found no evidence for behavioural or neurophysiological changes following tDCS over left M1 or left DLPFC in learning a complex bimanual task.
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http://dx.doi.org/10.1038/srep35739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5078840PMC
October 2016

Alterations in brain white matter contributing to age-related slowing of task switching performance: The role of radial diffusivity and magnetization transfer ratio.

Hum Brain Mapp 2016 11;37(11):4084-4098

Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Leuven, Belgium.

Successfully switching between tasks is critical in many daily activities. Age-related slowing of this switching behavior has been documented extensively, but the underlying neural mechanisms remain unclear. Here, we investigated the contribution of brain white matter changes associated with myelin alterations to age-related slowing of switching performance. Diffusion tensor imaging derived radial diffusivity (RD) and magnetization transfer imaging derived magnetization transfer ratio (MTR) were selected as myelin sensitive measures. These metrics were studied in relation to mixing cost (i.e., the increase in reaction time during task blocks that require task switching) on a local-global switching task in young (n = 24) and older (n = 22) adults. Results showed that higher age was associated with widespread increases in RD and decreases in MTR, indicative of white matter deterioration, possibly due to demyelination. Older adults also showed a higher mixing cost, implying slowing of switching performance. Finally, mediation analyses demonstrated that decreases in MTR of the bilateral superior corona radiata contributed to the observed slowing of switching performance with increasing age. These findings provide evidence for a role of cortico-subcortical white matter changes in task switching performance deterioration with healthy aging. Hum Brain Mapp 37:4084-4098, 2016. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/hbm.23297DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6867406PMC
November 2016

Cortical grey matter content is associated with both age and bimanual performance, but is not observed to mediate age-related behavioural decline.

Brain Struct Funct 2017 01 28;222(1):437-448. Epub 2016 Apr 28.

Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Tervuursevest 101, 3001, Heverlee, Belgium.

Declines in both cortical grey matter and bimanual coordination performance are evident in healthy ageing. However, the relationship between ageing, bimanual performance, and grey matter loss remains unclear, particularly across the whole adult lifespan. Therefore, participants (N = 93, range 20-80 years) performed a complex Bimanual Tracking Task, and structural brain images were obtained using magnetic resonance imaging. Analyses revealed that age correlated negatively with task performance. Voxel-based morphometry analysis revealed that age was associated with grey matter declines in task-relevant cortical areas and that grey matter in these areas was negatively associated with task performance. However, no evidence for a mediating effect of grey matter in age-related bimanual performance decline was observed. We propose a new hypothesis that functional compensation may account for the observed absence of mediation, which is in line with the observed pattern of increased inter-individual variance in performance with age.
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http://dx.doi.org/10.1007/s00429-016-1226-9DOI Listing
January 2017

Touching the Lived Body in Patients with Medically Unexplained Symptoms. How an Integration of Hands-on Bodywork and Body Awareness in Psychotherapy may Help People with Alexithymia.

Front Psychol 2016 29;7:253. Epub 2016 Feb 29.

Rehabilitation Research Center - Biomedical Research Center, Faculty of Medicine and Life Sciences, University of Hasselt Hasselt, Belgium.

Medically unexplained symptoms (MUS) are a considerable presenting problem in general practice. Alexithymia and difficulties with mental elaboration of bodily arousal are hypothesized as a key mechanism in MUS. In turn, this inability influences the embodied being and participating of these patients in the world, which is coined as 'the lived body' and underlies what is mostly referred to as body awareness (BA). The present article explores a more innovative hypothesis how hands-on bodywork can influence BA and serve as a rationale for a body integrated psychotherapeutic approach of MUS. Research not only shows that BA is a bottom-up 'bodily' affair but is anchored in a interoceptive-insular pathway (IIP) which in turn is deeply connected with autonomic and emotional brain areas as well as verbal and non-verbal memory. Moreover, it is emphasized how skin and myofascial tissues should be seen as an interoceptive generator, if approached in the proper manual way. This article offers supportive evidence explaining why a 'haptic' touch activates this IIP, restores the myofascial armored body, helps patients rebalancing their window of tolerance and facilitates BA by contacting their bodily inner-world. From a trans-disciplinary angle this article reflects on how the integration of bodywork with non-directive verbal guidance can be deeply healing and resourcing for the lived body experience in MUS. In particular for alexithymic patients this approach can be of significance regarding their representational failure of bodily arousal.
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http://dx.doi.org/10.3389/fpsyg.2016.00253DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4770185PMC
March 2016

Transcranial direct current stimulation in Parkinson's disease: Neurophysiological mechanisms and behavioral effects.

Neurosci Biobehav Rev 2015 Oct 20;57:105-17. Epub 2015 Aug 20.

Neuromotor Rehabilitation Research Group, Department of Rehabilitation Sciences, KU Leuven, Tervuursevest 101, B-3001 Leuven, Belgium. Electronic address:

Recent research has highlighted the potential of transcranial direct current stimulation (tDCS) to complement rehabilitation effects in the elderly and in patients with neurological diseases, including Parkinson's disease (PD). TDCS can modulate cortical excitability and enhance neurophysiological mechanisms that compensate for impaired learning in PD. The objective of this systematic review is to provide an overview of the effects of tDCS on neurophysiological and behavioral outcome measures in PD patients, both as a stand-alone and as an adjunctive therapy. We systematically reviewed the literature published throughout the last 10 years. Ten studies were included, most of which were sham controlled. Results confirmed that tDCS applied to the motor cortex had significant results on motor function and to a lesser extent on cognitive tests. However, the physiological mechanism underlying the long-term effects of tDCS on cortical excitability in the PD brain are still unclear and need to be clarified in order to apply this technique optimally to a wider population in the different disease stages and with different medication profiles.
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http://dx.doi.org/10.1016/j.neubiorev.2015.08.010DOI Listing
October 2015

Subcortical volumetric changes across the adult lifespan: subregional thalamic atrophy accounts for age-related sensorimotor performance declines.

Cortex 2015 Apr 26;65:128-38. Epub 2015 Jan 26.

Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Biomedical Sciences Group, Department of Kinesiology, KU Leuven, Belgium; Leuven Research Institute for Neuroscience & Disease (LIND), KU Leuven, Belgium. Electronic address:

Even though declines in sensorimotor performance during healthy aging have been documented extensively, its underlying neural mechanisms remain unclear. Here, we explored whether age-related subcortical atrophy plays a role in sensorimotor performance declines, and particularly during bimanual manipulative performance (Purdue Pegboard Test). The thalamus, putamen, caudate and pallidum of 91 participants across the adult lifespan (ages 20-79 years) were automatically segmented. In addition to studying age-related changes in the global volume of each subcortical structure, local deformations within these structures, indicative of subregional volume changes, were assessed by means of recently developed shape analyses. Results showed widespread age-related global and subregional atrophy, as well as some notable subregional expansion. Even though global atrophy failed to explain the observed performance declines with aging, shape analyses indicated that atrophy in left and right thalamic subregions, specifically subserving connectivity with the premotor, primary motor and somatosensory cortical areas, mediated the relation between aging and performance decline. It is concluded that subregional volume assessment by means of shape analyses offers a sensitive tool with high anatomical resolution in the search for specific age-related associations between brain structure and behavior.
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http://dx.doi.org/10.1016/j.cortex.2015.01.003DOI Listing
April 2015

Changes in corticomotor excitability and intracortical inhibition of the primary motor cortex forearm area induced by anodal tDCS.

PLoS One 2014 7;9(7):e101496. Epub 2014 Jul 7.

Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Leuven, Belgium; Neural Control of Movement Laboratory, Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland.

Objective: Previous studies have investigated how tDCS over the primary motor cortex modulates excitability in the intrinsic hand muscles. Here, we tested if tDCS changes corticomotor excitability and/or cortical inhibition when measured in the extensor carpi radialis (ECR) and if these aftereffects can be successfully assessed during controlled muscle contraction.

Methods: We implemented a double blind cross-over design in which participants (n = 16) completed two sessions where the aftereffects of 20 min of 1 mA (0.04 mA/cm2) anodal vs sham tDCS were tested in a resting muscle, and two more sessions where the aftereffects of anodal vs sham tDCS were tested in an active muscle.

Results: Anodal tDCS increased corticomotor excitability in ECR when aftereffects were measured with a low-level controlled muscle contraction. Furthermore, anodal tDCS decreased short interval intracortical inhibition but only when measured at rest and after non-responders (n = 2) were removed. We found no changes in the cortical silent period.

Conclusion: These findings suggest that targeting more proximal muscles in the upper limb with anodal tDCS is achievable and corticomotor excitability can be assessed in the presence of a low-level controlled contraction of the target muscle.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101496PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084808PMC
February 2015

Optimization of the transcranial magnetic stimulation protocol by defining a reliable estimate for corticospinal excitability.

PLoS One 2014 24;9(1):e86380. Epub 2014 Jan 24.

REVAL Rehabilitation Research Centre, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium ; Motor Control Laboratory, Research Center for Movement Control and Neuroplasticity, Department of Biomedical Kinesiology, Group Biomedical Sciences, K.U. Leuven, Heverlee, Belgium.

The goal of this study was to optimize the transcranial magnetic stimulation (TMS) protocol for acquiring a reliable estimate of corticospinal excitability (CSE) using single-pulse TMS. Moreover, the minimal number of stimuli required to obtain a reliable estimate of CSE was investigated. In addition, the effect of two frequently used stimulation intensities [110% relative to the resting motor threshold (rMT) and 120% rMT] and gender was evaluated. Thirty-six healthy young subjects (18 males and 18 females) participated in a double-blind crossover procedure. They received 2 blocks of 40 consecutive TMS stimuli at either 110% rMT or 120% rMT in a randomized order. Based upon our data, we advise that at least 30 consecutive stimuli are required to obtain the most reliable estimate for CSE. Stimulation intensity and gender had no significant influence on CSE estimation. In addition, our results revealed that for subjects with a higher rMT, fewer consecutive stimuli were required to reach a stable estimate of CSE. The current findings can be used to optimize the design of similar TMS experiments.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086380PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901672PMC
October 2014

A single session of 1 mA anodal tDCS-supported motor training does not improve motor performance in patients with multiple sclerosis.

Restor Neurol Neurosci 2014 ;32(2):293-300

BIOMED, Biomedical Research Institute, Hasselt University, Agoralaan, Diepenbeek, Belgium REVAL Research Institute, Hasselt University, Agoralaan, Diepenbeek, Belgium Motor Control Laboratory, Research Center for Movement Control and Neuroplasticity, Research Center for Movement Control and Neuroplasticity, Group Biomedical Sciences, K.U. Leuven, Tervuursevest, Heverlee, Belgium.

Purpose: To assess the effects of atDCS on motor performance in patients with multiple sclerosis (MS). Previously, anodal transcranial direct current stimulation (atDCS) has been shown to improve motor performance in healthy subjects and neurodegenerative populations. However, the effect of atDCS on motor performance is not examined in MS.

Methods: In the current study, a sham controlled double-blind crossover design was used to evaluate the effect of 20 minutes of 1 mA atDCS or sham tDCS (stDCS) on a unimanual motor sequence-training task, consisting of sequential finger presses on a computer keyboard with the most impaired hand. Patients received stimulation (atDCS or stDCS) during motor training. tDCS was applied over the primary motor cortex contralateral to the most impaired hand. Motor performance was assessed immediately before, during and 30 minutes after stimulation.

Results: Although we need to be careful with the interpretation of the data due to lack of power, our results showed no significant effect of atDCS on motor performance.

Conclusions: Our findings indicate that atDCS-supported motor training was not able to improve motor performance more than sham-supported motor training. Possibly, the effects of atDCS are mediated by specific MS-related characteristics. Furthermore, increasing atDCS intensity and offering multiple stimulation sessions might be necessary to optimize motor performance resulting from atDCS-supported motor training.
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http://dx.doi.org/10.3233/RNN-130348DOI Listing
November 2014

Anodal tDCS increases corticospinal output and projection strength in multiple sclerosis.

Neurosci Lett 2013 Oct 12;554:151-5. Epub 2013 Sep 12.

BIOMED, Biomedical Research Institute, Hasselt University, Agoralaan, Building C, B-3590 Diepenbeek, Belgium; REVAL Research Institute, Hasselt University, Agoralaan, Building A, B-3590 Diepenbeek, Belgium; Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Group Biomedical Sciences, KU Leuven, Tervuursevest 101, B-3001 Heverlee, Belgium. Electronic address:

The application of anodal transcranial direct current stimulation (atDCS) to the human brain has been shown to elicit corticospinal (CS) excitability changes. This study evaluated the effect of a single session of atDCS on CS excitability in patients with multiple sclerosis (MS). atDCS and sham tDCS (stDCS) were applied to the primary motor cortex (M1) contralateral to the more severely impaired hand for 20min in a double-blinded crossover design. Changes in CS excitability were assessed using transcranial magnetic stimulation (TMS). The area under the recruitment curves increased significantly after application of atDCS (+56.58%, p=0.023) but not after stDCS. A sigmoidal curve-analysis revealed a higher plateau of the curve after atDCS (+22.2%, p<0.001). Our results showed that atDCS over M1 has the ability to increase CS output and projection strength in MS-patients, suggesting that atDCS can be considered during neural rehabilitation to facilitate motor recovery in MS.
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http://dx.doi.org/10.1016/j.neulet.2013.09.004DOI Listing
October 2013

Task-specific effect of transcranial direct current stimulation on motor learning.

Front Hum Neurosci 2013 1;7:333. Epub 2013 Jul 1.

KU Leuven, Kinesiology and Rehabilitation Sciences, Research Center for Movement Control and Neuroplasticity , Heverlee , Belgium.

Transcranial direct current stimulation (tDCS) is a relatively new non-invasive brain stimulation technique that modulates neural processes. When applied to the human primary motor cortex (M1), tDCS has beneficial effects on motor skill learning and consolidation in healthy controls and in patients. However, it remains unclear whether tDCS improves motor learning in a general manner or whether these effects depend on which motor task is acquired. Here we compare whether the effect of tDCS differs when the same individual acquires (1) a Sequential Finger Tapping Task (SEQTAP) and (2) a Visual Isometric Pinch Force Task (FORCE). Both tasks have been shown to be sensitive to tDCS applied over M1, however, the underlying processes mediating learning and memory formation might benefit differently from anodal transcranial direct current stimulation (anodal-tDCS). Thirty healthy subjects were randomly assigned to an anodal-tDCS group or sham-group. Using a double-blind, sham-controlled cross-over design, tDCS was applied over M1 while subjects acquired each of the motor tasks over three consecutive days, with the order being randomized across subjects. We found that anodal-tDCS affected each task differently: the SEQTAP task benefited from anodal-tDCS during learning, whereas the FORCE task showed improvements only at retention. These findings suggest that anodal-tDCS applied over M1 appears to have a task-dependent effect on learning and memory formation.
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http://dx.doi.org/10.3389/fnhum.2013.00333DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3696911PMC
July 2013

Is motor learning mediated by tDCS intensity?

PLoS One 2013 24;8(6):e67344. Epub 2013 Jun 24.

BIOMED-Biomedical Research Institute, Hasselt University, Diepenbeek, Belgium.

Although tDCS has been shown to improve motor learning, previous studies reported rather small effects. Since physiological effects of tDCS depend on intensity, the present study evaluated this parameter in order to enhance the effect of tDCS on skill acquisition. The effect of different stimulation intensities of anodal tDCS (atDCS) was investigated in a double blind, sham controlled crossover design. In each condition, thirteen healthy subjects were instructed to perform a unimanual motor (sequence) learning task. Our results showed (1) a significant increase in the slope of the learning curve and (2) a significant improvement in motor performance at retention for 1.5 mA atDCS as compared to sham tDCS. No significant differences were reported between 1 mA atDCS and sham tDCS; and between 1.5 mA atDCS and 1 mA atDCS.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067344PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3691194PMC
February 2014