1,721,108 research outputs found
No evidence for a difference in lateralization and distinctiveness level of transcranial magnetic stimulation-derived cortical motor representations over the adult lifespan
No full textThis study aimed to investigate the presence and patterns of age-related differences in TMS-based measures of lateralization and distinctiveness of the cortical motor representations of two different hand muscles. In a sample of seventy-three right-handed healthy participants over the adult lifespan, the first dorsal interosseus (FDI) and abductor digiti minimi (ADM) cortical motor representations of both hemispheres were acquired using transcranial magnetic stimulation (TMS). In addition, dexterity and maximum force levels were measured. Lateralization quotients were calculated for homolog behavioral and TMS measures, whereas the distinctiveness between the FDI and ADM representation within one hemisphere was quantified by the center of gravity (CoG) distance and cosine similarity. The presence and patterns of age-related changes were examined using linear, polynomial, and piecewise linear regression. No age-related differences could be identified for the lateralization quotient of behavior or cortical motor representations of both intrinsic hand muscles. Furthermore, no evidence for a change in the distinctiveness of the FDI and ADM representation with advancing age was found. In conclusion this work showed that lateralization and distinctiveness of cortical motor representations, as determined by means of TMS-based measures, remain stable over the adult lifespan.sponsorship: Fonds Wetenschappelijk Onderzoek|11F6921N, KU Leuven|C16/15/070, Fonds Wetenschappelijk Onderzoek|EOS 30446199, MEMODYN, Fonds Wetenschappelijk Onderzoek|11L9322N, Fonds Wetenschappelijk Onderzoek|AUHL/11/01 (R-3987), Fonds Wetenschappelijk Onderzoek|G039821N, Fonds Wetenschappelijk Onderzoek|I005018Nstatus: Published onlin
GABA, Glx, and GSH in the cerebellum: their role in motor performance and learning across age groups
No full textIntroduction The cerebellum is essential for motor control and learning, relying on structural and functional integrity. Age-related atrophy leads to Purkinje cell loss, but subtle neurochemical changes in GABA, Glx (glutamate + glutamine), and glutathione (GSH) may precede degeneration and contribute to motor decline.Methods 25 younger (YA) and 25 older adults (OA) were included in this study. Magnetic resonance spectroscopy (MRS), using the MEGA-PRESS sequence, was used to investigate how age affects GABA, Glx and GSH levels in the right cerebellar hemisphere, and their relationship with motor performance, measured using a visuomotor bimanual tracking task (BTT).Results In line with previous work YA outperformed OA on both the simple and complex task variants of the BTT. Furthermore, YA demonstrated faster short-term motor learning as compared to OA. On the metabolic level, no significant age group differences in cerebellar GABA, Glx or GSH levels, nor any task-related modulation of GABA or Glx were observed. Additionally, neither baseline neurometabolite levels nor their modulation predicted motor performance or learning.Discussion These results align with previous research suggesting that neurometabolic aging is region-specific, with the cerebellum potentially being more resilient due to its slower aging process. Since neither baseline nor task-related modulation of GABA, Glx, or GSH predicted motor performance or learning, cerebellar neurometabolite concentrations may not directly underlie age-related behavioral changes. Instead, volumetric decline and changes in structural and functional connectivity in the aging cerebellum may play a more significant role in motor decline as compared to neurochemical alterations. Nonetheless, it is important to consider that motor performance and learning rely on distributed brain networks-including cortical and subcortical structures-which also undergo age-related changes and may contribute to observed behavioral declines. While our findings do not support a direct role of cerebellar neurometabolite levels in age-related motor performance differences, they underscore the complexity of neurochemical aging.The author(s) declare that financial support was received for the research and/or publication of this article. This work was supported by the Research Foundation Flanders grant (G039821N). SVM (11L9322N), MH (11F6921N), and RB (1SD8323N) were funded by a grant from the Research Foundation Flanders. SVM (BOF21INCENT15) was supported by the UHasselt Special Research Fund grant. MH was supported by the KU Leuven Special Research
Fund (PDMT2/24/077)
Aging, brain plasticity, and motor learning
No full textMotor skill learning, the process of acquiring new motor skills, is critically important across the lifespan, from
early development through adulthood and into older age, as well as in pathological conditions (i.e., rehabilitation).
Extensive research has demonstrated that motor skill acquisition in young adults is accompanied by
significant neuroplastic changes, including alterations in brain structure (gray and white matter), function (i.e.,
activity and connectivity), and neurochemistry (i.e., levels of neurotransmitters). In the aging population, motor
performance typically declines, characterized by slower and less accurate movements. However, despite these
age-related changes, older adults maintain the capacity for skill improvement through training. In this review,
we explore the extent to which the aging brain retains the ability to adapt in response to motor learning, specifically
whether skill acquisition is accompanied by neural changes. Furthermore, we discuss the associations
between inter-individual variability in brain structure and function and the potential for future learning in older
adults. Finally, we consider the use of non-invasive brain stimulation techniques aimed at optimizing motor
learning in this population. Our review provides insights into the neurobiological underpinnings of motor
learning in older adults and emphasizes strategies to enhance their motor skill acquisition.This work was supported by the Research Fund KU Leuven (C16/15/ 070), the Research Foundation Flanders grant (G089818N, G039821N), and the Excellence of Science grant (EOS 30446199, MEMODYN), awarded to S.P. Swinnen and colleagues. Melina Hehl was funded by a fellowship grant from Research Foundation Flanders (11F6921N; V434023N) and Research Fund KU Leuven (PDMT2/24/077). This work was additionally supported by grants from the KU Leuven (STG/21/018) and from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 794042, awarded to Jolien Gooijers and Caroline Seer, respectively. Additionally, Caroline Seer was funded by a postdoctoral fellowship from the Research Foundation – Flanders (179732). The authors declare no competing financial interests. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Dual-site TMS as a tool to probe effective interactions within the motor network: a review
No full textDual-site transcranial magnetic stimulation (ds-TMS) is well suited to investigate the causal effect of distant brain regions on the primary motor cortex, both at rest and during motor performance and learning. However, given the broad set of stimulation parameters, clarity about which parameters are most effective for identifying particular interactions is lacking. Here, evidence describing inter- and intra-hemispheric interactions during rest and in the context of motor tasks is reviewed. Our aims are threefold: (1) provide a detailed overview of ds-TMS literature regarding inter- and intra-hemispheric connectivity; (2) describe the applicability and contributions of these interactions to motor control, and; (3) discuss the practical implications and future directions. Of the 3659 studies screened, 109 were included and discussed. Overall, there is remarkable variability in the experimental context for assessing ds-TMS interactions, as well as in the use and reporting of stimulation parameters, hindering a quantitative comparison of results across studies. Further studies examining ds-TMS interactions in a systematic manner, and in which all critical parameters are carefully reported, are needed.sponsorship: This work was supported by the KU Leuven Special Research Fund grant (C16/15/070), Research Foundation Flanders grant (G089818N and G039821N), and the Excellence of Science grant (EOS 30446199, MEMODYN). SVM (11L9322N) and MH (11F6921N) are funded by a grant from the Research Foundation Flanders. SVM is supported by the UHasselt Special Research Fund grant (BOF21INCENT15). (KU Leuven Special Research Fund grant|C16/15/070, Research Foundation Flanders grant|G089818N, Research Foundation Flanders grant|G039821N, Excellence of Science grant|EOS 30446199, Research Foundation Flanders|11L9322N, Research Foundation Flanders|11F6921N, UHasselt Special Research Fund grant|BOF21INCENT15)status: Published onlin
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
Causal involvement of DLPFC during bimanual coordination in older adults - an rTMS study
No full textThe role of the dorsolateral prefrontal cortex (DLPFC) in the regulation of bimanual coordination appears to become crucial with aging. Age-related changes in the involvement of the DLPFC in bimanual coordination were studied by using disruptive repetitive TMS (rTMS), inducing a transient lesion in this brain structure. Neurophysiological as well as behavioral effects of suppressing DLPFC during the preparation and execution of a bimanual task were studied in 41 healthy adults (young and old). Specifically, we combined short-train rTMS with single pulse TMS to examine the effect of DLPFC suppression on the interhemispheric projection to the contralateral primary motor cortex (M1) during motor preparation. Findings revealed that compromised interhemispheric DLPFC-M1 disinhibition during motor preparation in older adults resulted in less accurate bimanual performance. The altered DLPFC-M1 interaction in older adults appeared to result from a decline in local inhibitory mechanisms in the DLPFC. In addition, the induction of DLPFC suppression affected task accuracy, but not movement stability in both age groups. Taken together, these results suggest that DLPFC acts as a key regulator in the control of bimanual movement coordination
The Reciprocal Relationship Between Short- and Long-Term Motor Learning and Neurometabolites
No full textSkill acquisition requires practice to stimulate neuroplasticity. Changes in inhibitory and excitatory neurotransmitters, such as gamma-aminobutyric acid (GABA) and glutamate, are believed to play a crucial role in promoting neuroplasticity. Magnetic resonance spectroscopy (MRS) at 3 T, using the MEGA-PRESS sequence, and behavioral data were collected from 62 volunteers. Participants completed a 4-week protocol, practicing either complex (n = 32) or simple (n = 30) bimanual tracking tasks (BTT). Neurotransmitter levels and skill levels at baseline, after 2 and 4 weeks of motor training were compared for the left and right primary sensorimotor cortex (SM1) and the left dorsal premotor cortex (PMd). Furthermore, task-related modulations of neurotransmitter levels in the left PMd were assessed. The study yielded that baseline neurotransmitter levels in motor-related brain regions predicted training success. Furthermore, lower GABA+ (p = 0.0347) and higher Glx (glutamate + glutamine compound) levels (p = 0.0234) in left PMd correlated with better long-term learning of simple and complex tasks, respectively, whereas higher GABA+ in right SM1 correlated with complex task learning (p = 0.0064). Resting neurometabolite levels changed during the intervention: Left SM1 Glx decreased with complex training toward Week 4 (p = 0.0135), whereas right SM1 Glx was increased at Week 2 (p = 0.0043), regardless of training type. Group-level analysis showed no task-related neurometabolite modulation in the left PMd. However, individual baseline GABA+ and Glx modulation influenced short-term motor learning (interaction: p = 0.0213). These findings underscore the importance of an interplay between inhibitory and excitatory neurotransmitters during motor learning and suggest potential for future personalized approaches to optimize motor learning.This work was supported by Research Fund KU Leuven (C16/15/070), the Research Foundation Flanders grant (G089818N, G039821N), the Excellence of Science grant (EOS 30446199, MEMODYN), and the Hercules fund AUHL/11/01 (R-3987) and I005018N. Melina Hehl is funded by a fellowship grant from Research Foundation Flanders (11F6921N) and a KU Leuven Special Research Fund (PDMT2/24/077). Shanti Van Malderen is funded by
a fellowship grant from Research Foundation Flanders (11L9322N) and an UHasselt Special Research Fund (BOF21INCENT15). Svitlana Blashchuk is funded by an UHasselt Special Research Fund (BOF24DOC13)
Neurometabolic Correlates of Reactive and Proactive Motor Inhibition in Young and Older Adults: Evidence from Multiple Regional 1H-MR Spectroscopy
No full textSuboptimal inhibitory control is a major factor contributing to motor/cognitive deficits in older age and pathology. Here, we
provide novel insights into the neurochemical biomarkers of inhibitory control in healthy young and older adults and
highlight putative neurometabolic correlates of deficient inhibitory functions in normal aging. Age-related alterations in
levels of glutamate–glutamine complex (Glx), N-acetylaspartate (NAA), choline (Cho), and myo-inositol (mIns) were assessed
in the right inferior frontal gyrus (RIFG), pre-supplementary motor area (preSMA), bilateral sensorimotor cortex (SM1),
bilateral striatum (STR), and occipital cortex (OCC) with proton magnetic resonance spectroscopy (1H-MRS). Data were
collected from 30 young (age range 18–34 years) and 29 older (age range 60–74 years) adults. Associations between
age-related changes in the levels of these metabolites and performance measures or reactive/proactive inhibition were
examined for each age group. Glx levels in the right striatum and preSMA were associated with more efficient proactive
inhibition in young adults but were not predictive for reactive inhibition performance. Higher NAA/mIns ratios in the
preSMA and RIFG and lower mIns levels in the OCC were associated with better deployment of proactive and reactivesponsorship: Excellence of Science|30446199, Francqui Foundation|813120, Research Foundation|G.089818N, Francqui Foundation|316679, KU Leuven Special Research Fund|C16/15/070status: Published onlin
Continuous theta burst stimulation at 30 hz does not modulate cortical excitability in a sham-controlled study
No full textAbstract Theta burst stimulation (TBS) can modulate cortical excitability but suffers from high inter-subject variability. Modified TBS frequency patterns (30 Hz) showed consistent inhibitory aftereffects, but further research into the time course of these effects is needed. This study aimed to investigate the efficacy of a 30 Hz continuous TBS (cTBS) protocol. Participants (n = 20) underwent an experimental session (real cTBS) and a control session (sham cTBS). To assess cortical excitability, Transcranial Magnetic Stimulation was applied over the primary motor cortex before cTBS, and at five timepoints after cTBS. Percentage change (PC) to baseline was analysed using a Linear Mixed Model. No difference in PC was found between real and sham cTBS (p = 0.696). Our results demonstrate a significant increase in PC over time (p = 0.006) at 30, (p = 0.01), 45 (p = 0.027), and 55 min (p = 0.024) post cTBS, irrespective of condition. Secondary analysis dividing the sample into responders and paradox-responders showed no significant predictors for cTBS responsiveness. We could not replicate previously reported suppressive effects of 30 Hz cTBS. Increases in MEP amplitudes over a 60-minute time window were independent of stimulation condition and marked by high inter-subject variability. Validations of modified TBS protocols are further needed to replicate findings and understand mechanisms underlying individuals’ responsiveness
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