Time course of motor excitability before and after a task-related movement

Abstract

Aims of the study. -The time course of motor excitability during a task-related unilateral right thumb movement was studied using sub-threshold transcranial magnetic stimulation (TMS) to the contralateral left motor cortex. The level of stimulation evoked a motor evoked potential (MEP) in the thumb when the subject was at rest in approximately 10% of the trials.Methods. -Subjects made a brief right thumb movement to the predictable omission of regularly presented tone bursts allowing experimental definition of TMS relative to the cue to move. Motor cortical excitability was characterized by amplitude and/or probability of eliciting MEPs.Results. -There were four periods of altered motor excitability during task performance compared to a control resting state: a first period of weak facilitation before movement between -500 to -200 ms, a second period without increased excitability approximately 150 ms before movement onset when MEPs amplitude was below that seen in rest, a third period of strong facilitation between -100 ms before movement and +200 ms after facilitation and a fourth period of weak facilitation between +200 to +500 ms.Conclusion. -These results show that during performance of a task requiring a motor response, motor cortical excitability is increased above resting for hundreds of millisecond before and after the response, except for a transient period between 75 and 150 ms prior to movement onset. The temporal pattern of these excitability changes is compatible with multiple excitatory and inhibitory inputs interacting on motor cortex.© 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. RésuméObjectif de l'étude. -Étudier le décours temporel de l'excitabilité motrice pendant une tâche de mouvement du pouce droit, en délivrant une stimulation magnétique transcranienne (TMS) à un niveau infra-liminaire sur le cortex moteur contralatéral. À ce niveau de stimulation, nous avons obtenu l'apparition d'un potentiel évoqué moteur (PEM) dans le pouce, avec les sujets au repos, dans 10 % des essais.Méthodes. -Les sujets faisaient un bref mouvement du pouce droit en réponse à l'omission (prédictible) de bruits blancs présentés régulièrement. Ceci nous a permis de définir différentes fenêtres d'application de la TMS, avant ou après le mouvement du doigt. L'excitabilité motrice corticale était alors définie par l'amplitude et/ou la probabilité de produire un PEM.Résultats. -Il est apparu 4 périodes au cours desquelles l'excitabilité motrice était altérée en comparaison à un niveau de repos : une première période de faible facilitation avant le mouvement, entre -500 et -200 ms, une seconde période sans augmentation de l'excitabilité, environ 150 ms avant le début du mouvement (l'amplitude des PEM étant inférieure à celle pendant les périodes de repos), une troisième période de forte facilitation entre -100 ms avant le mouvement et +200 ms après la facilitation, enfin une quatrième période de faible facilitation entre +200 et +500 ms.Conclusion. -Ces résultats montrent que, pend...

Driving Human Motor Cortical Oscillations Leads to Behaviorally Relevant Changes in Local GABAAInhibition: A tACS-TMS Study

“…Based on the state and frequency dependency of tACS effects (Feurra et al, 2013; Neuling et al, 2013; Santarnecchi et al, 2013) and the well recognized distinct patterns of changes in beta and gamma frequency power as well as cortical excitability during movement preparation (Pfurtscheller and Lopes da Silva, 1999; Reynolds and Ashby, 1999; Zaaroor et al, 2003; Muthukumaraswamy, 2010), here, for the first time, we also evaluated whether externally driving oscillatory activity at these frequencies can lead to plastic changes in cortical excitability, as indexed during movement preparation. We did not find any after-effect of tACS on these measures.…”

Electroencephalographic evidence for pre‐motor cortex activation during inspiratory loading in humans

“…In this respect, Locher et al (2006) have shown that IRL could facilitate the diaphragm response to transcranial magnetic stimulation, but in a manner suggestive of a spinal rather than cortical mechanism. Because a pre‐motor negativity can facilitate the response of the target muscle to transcranial magnetic stimulation (Zaaroor et al 2003), Locher et al (2006) hypothesized that their observations could reflect increased pre‐motor inputs to the phrenic motoneurones. By confirming that the pre‐motor cortex is most likely to be involved in the compensation of inspiratory loads, the present study lends support to this hypothesis.…”

Deficient intracortical inhibition (SICI) during movement preparation after chronic stroke

“…[1][2][3] Interactions between intracortical inhibitory and excitatory processes within the primary motor cortex (M1) are crucial for motor control and change in the process of generation of a voluntary movement (at the immediate premovement stage). [4][5][6][7][8][9][10][11] GABAergically mediated short intracortical inhibition (SICI) can be studied using a wellestablished paired pulse transcranial magnetic stimulation (TMS) method. 12 Previous work demonstrated premovement modulation of SICI, characterized by a release from inhibition (disinhibition) prior to the onset of a voluntary movement in healthy subjects.…”

“…12 Previous work demonstrated premovement modulation of SICI, characterized by a release from inhibition (disinhibition) prior to the onset of a voluntary movement in healthy subjects. [7][8][9] The ability to evaluate SICI in association with performance of a voluntary movement added another perspective to our understanding of intracortical inhibitory circuits and, in fact, seems to enhance the specificity of this technique for some pathologic states of the central motor system. For example, in patients with dystonia, premovement SICI and SICI at rest showed substantially different effects with reduction in SICI at rest and persistent lack of modulation of SICI during movement preparation.…”

“…15,[17][18][19] Movement-related changes in SICI in stroke patients intending to move the paretic hand have not been investigated. Here, we hypothesized that dynamic modulation of premovement SICI, as described in healthy subjects, [7][8][9] would be impaired in the ipsilesional M1 of chronic stroke patients moving the paretic hand.…”