scholarly journals Challenging the function of motor inhibition: Does it really assist action selection?

2018 ◽  
Author(s):  
Caroline Quoilin ◽  
Fanny Fievez ◽  
Julie Duque
Keyword(s):  
Primary Motor Cortex ◽  
Index Finger ◽  
Motor Evoked Potentials ◽  
Action Selection ◽  
Prime Mover ◽  
Strong Suppression ◽  
Action Preparation ◽  
Contralateral Hand ◽  
Simple Rt

By applying transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to elicit motor-evoked potentials (MEPs) in muscles of the contralateral hand during reaction time (RT) tasks, many studies have reported a strong suppression of MEPs during action preparation, a phenomenon called preparatory inhibition. Several hypotheses have been put forward regarding the role of this inhibition, with the predominant view suggesting that it would help action selection. However, this assumption is still a matter of debate. Here, we aimed at directly addressing this idea by comparing MEPs in a task that required subjects to select a finger response within a set of predefined options (choice RT task: left or right index finger abduction) or when subjects simply had to provide the same finger response on every trial, in the absence of choice (simple RT task). Moreover, we minimized any effect that could be associated with other forms of inhibition. In both versions of the task, TMS was applied on both M1 (double-coil protocol) at several time points between the go signal and the left or right index finger response, eliciting MEPs bilaterally in the prime mover (index finger agonist) and in an irrelevant muscle (pinky agonist). Overall, MEP suppression was moderate in this study; it was only found for the irrelevant muscle. As such, MEPs in the index agonist were facilitated when elicited in a responding hand (e.g. left MEPs preceding left responses) and remained mostly unchanged in a non-responding hand (e.g. left MEPs preceding right responses). In contrast, MEPs were almost always suppressed in the pinky muscle when elicited in the non-responding hand and sometimes also in the responding hand. Importantly, this effect was more consistent in the choice than in the simple RT task, supporting the view that preparatory inhibition may assist action selection. Moreover, the fact that it sometimes concerned the responding hand is coherent with the idea of a global process, suppressing broadly the motor system.

scholarly journals The Effect of Bilateral Isometric Forces in Different Directions on Motor Cortical Function in Humans

2010 ◽  
Vol 104 (6) ◽  
pp. 2922-2931 ◽  
Author(s):  
Juliette A. Yedimenko ◽  
Monica A. Perez
Keyword(s):  
Primary Motor Cortex ◽  
Index Finger ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
The Body ◽  
Body Midline ◽  
Cortical Function ◽  
Intracortical Circuits ◽  
The Right ◽  
Isometric Forces

The activity in the primary motor cortex (M1) reflects the direction of movements, but little is known about physiological changes in the M1 during generation of bilateral isometric forces in different directions. Here, we used transcranial magnetic stimulation to examine motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), and interhemispheric inhibition (IHI) in the left first dorsal interosseous (FDI) during isometric index finger abduction while the right index finger remained at rest or performed isometric forces in different directions (abduction or adduction) and in different postures (prone and supine). Left FDI MEPs were suppressed during bilateral compared with unilateral forces, with a stronger suppression when the right index finger force was exerted in the adduction direction regardless of hand posture. IHI targeting the left FDI increased during bilateral compared with unilateral forces and this increase was stronger during right index finger adduction despite the posture of the right hand. SICI decreased to a similar extent during both bilateral forces in both hand postures. Thus generation of index finger isometric forces away from the body midline (adduction direction), regardless of the muscle engaged in the task, down-regulates corticospinal output in the contralateral active hand to a greater extent than forces exerted toward the body midline (abduction direction). Transcallosal inhibition, but not GABAergic intracortical circuits, was modulated by the direction of the force. These findings suggest that during generation of bimanual isometric forces the M1 is driven by “extrinsic” parameters related to the hand action.

Task-Dependent Modulation of Inputs to Proximal Upper Limb Following Transcranial Direct Current Stimulation of Primary Motor Cortex

2010 ◽  
Vol 103 (5) ◽  
pp. 2382-2389 ◽  
Author(s):  
Lynley V. Bradnam ◽  
Cathy M. Stinear ◽  
Gwyn N. Lewis ◽  
Winston D. Byblow
Keyword(s):  
Motor Cortex ◽  
Upper Limb ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Silent Period ◽  
Hand Muscles ◽  
Before And After ◽  
Contralateral Hand ◽  
Left And Right ◽  
Period Duration

Cathodal transcranial DC stimulation (c-tDCS) suppresses excitability of primary motor cortex (M1) controlling contralateral hand muscles. This study assessed whether c-tDCS would have similar effects on ipsi- and contralateral M1 projections to a proximal upper limb muscle. Transcranial magnetic stimulation (TMS) of left M1 was used to elicit motor evoked potentials (MEPs) in the left and right infraspinatus (INF) muscle immediately before and after c-tDCS of left M1, and at 20 and 40 min, post-c-tDCS. TMS was delivered as participants preactivated each INF in isolation (left, right) or both INF together (bilateral). After c-tDCS, ipsilateral MEPs in left INF and contralateral MEPs in right INF were suppressed in the left task but not in the bilateral or right tasks, indicative of task-dependent modulation. Ipsilateral silent period duration in the left INF was reduced after c-tDCS, indicative of altered transcallosal inhibition. These findings may have implications for the use of tDCS as an adjunct to therapy for the proximal upper limb after stroke.

scholarly journals Changes in corticospinal excitability associated with motor learning by observing

2017 ◽  
Author(s):  
Heather R. McGregor ◽  
Michael Vesia ◽  
Cricia Rinchon ◽  
Robert Chen ◽  
Paul L. Gribble
Keyword(s):  
Motor Learning ◽  
Motor Skills ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Abductor Pollicis Brevis ◽  
Functional Changes ◽  
Hand Muscles ◽  
Before And After

AbstractWhile many of our motor skills are acquired through physical practice, we can also learn how to make movements by observing others. For example, individuals can learn how to reach in novel dynamical environments (‘force fields’, FF) by observing the movements of a tutor. Previous neurophysiology and neuroimaging studies in humans suggest a role for the motor system in motor learning by observing. Here we tested the role of primary motor cortex (M1) in motor learning by observing. We used single-pulse transcranial magnetic stimulation (TMS) to elicit motor evoked potentials (MEPs) in right hand muscles at rest. MEPs were elicited before and after participants observed either a video adapting her reaches to a FF or a control video showing a tutor performing reaches in an unlearnable FF. We predicted that observing motor learning would increase M1 excitability to a greater extent than observing movements that did not involve learning. We found that observing FF learning increased MEP amplitudes recorded from right first dorsal interosseous (FDI) and right abductor pollicis brevis (APB) muscles. There were no changes in MEP amplitudes for control participants who observed a tutor performing reaches in an unlearnable, randomly varying FF. The observed MEP changes can thus be specifically linked to observing motor learning. These results are consistent with the idea that observing motor learning produces functional changes in M1, or corticospinal networks or both.

scholarly journals Crossed corticospinal facilitation between arm and trunk muscles in humans

2018 ◽  
Vol 120 (5) ◽  
pp. 2595-2602 ◽  
Author(s):  
Shin-Yi Chiou ◽  
Paul H. Strutton ◽  
Monica A. Perez
Keyword(s):  
Primary Motor Cortex ◽  
Index Finger ◽  
Elbow Flexion ◽  
Voluntary Contraction ◽  
Erector Spinae ◽  
Trunk Muscles ◽  
Trunk Movements ◽  
Simultaneous Activation ◽  
Voluntary Contractions

A voluntary contraction of muscles with one arm increases the excitability of corticospinal projections to the contralateral resting arm, a phenomenon known as crossed facilitation. Although many motor tasks engage simultaneous activation of the arm and trunk, interactions between corticospinal projections targeting these segments remain largely unknown. Using transcranial magnetic stimulation over the trunk representation of the primary motor cortex, we examined motor-evoked potentials (MEPs) in the resting erector spinae (ES) muscle when the contralateral arm remained at rest or performed 20% of isometric maximal voluntary contraction (MVC) into index finger abduction, thumb abduction, elbow flexion, and elbow extension. We found that MEP size in the ES increased during all voluntary contractions, with greater facilitation occurring during elbow flexion and index finger abduction. To further examine the origin of changes in MEP size, we measured short-interval intracortical inhibition (SICI) and cervicomedullary MEPs (CMEPs) in the ES muscle during elbow flexion and index finger abduction and when the arm remained at rest. Notably, SICI decreased and CMEPs remained unchanged in the ES during both voluntary contractions compared with rest, suggesting a cortical origin for the effects. Our findings reveal crossed facilitatory interactions between trunk extensor and proximal and distal arm muscles, particularly for elbow flexor and index finger muscles, likely involving cortical mechanisms. These interactions might reflect the different role of these muscles during functionally relevant arm and trunk movements. NEW & NOTEWORTHY Many of the tasks of daily life involve simultaneous activation of the arm and trunk. We found that responses in the erector spinae muscles evoked by motor cortical stimulation increased in size during elbow flexion and extension and during index finger abduction and thumb abduction. Crossed facilitation with the trunk was more pronounced during elbow flexion and index finger abduction. These results might reflect the different role of these muscles during arm and trunk movements.

Role of Intracortical Inhibition in Selective Hand Muscle Activation

2003 ◽  
Vol 89 (4) ◽  
pp. 2014-2020 ◽  
Author(s):  
Cathy M. Stinear ◽  
Winston D. Byblow
Keyword(s):  
Muscle Activation ◽  
Primary Motor Cortex ◽  
Index Finger ◽  
Motor Evoked Potential ◽  
Intracortical Inhibition ◽  
Dominant Hand ◽  
Abductor Pollicis Brevis ◽  
Computer Mouse ◽  
Finger Flexion

Previous studies have shown that intracortical inhibition (ICI) plays an important role in shaping the output from primary motor cortex (M1). This study explored the muscle specificity and temporal modulation of ICI during the performance of a phasic index finger flexion task. Fifteen subjects were asked to rest their dominant hand on a computer mouse and depress the mouse button using their index finger in time with a 1-Hz auditory metronome, while keeping the rest of their hand as relaxed as possible. Responses to single- and paired-pulse transcranial magnetic stimulation were recorded from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles while subjects were at rest and during “on” and “off” phases of the task. For FDI during the on phase, motor evoked potential (MEP) amplitude and pretrigger EMG increased and ICI decreased, as expected. This pattern of modulation was also observed for APB in seven subjects. The remaining eight subjects demonstrated a decrease in MEP amplitude and increase in ICI for APB during the on phase. This was associated with significantly less APB activation during the on phase. These findings suggest that an increase in ICI and decrease in corticospinal excitability can prevent unwanted muscle activation in a muscle-specific, temporally modulated manner.

scholarly journals Corticospinal gating during action preparation and movement in the primate motor cortex

2018 ◽  
Vol 119 (4) ◽  
pp. 1538-1555 ◽  
Author(s):  
Demetris S. Soteropoulos
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Cell Activity ◽  
Active Role ◽  
Reach To Grasp ◽  
Inhibitory Circuits ◽  
Corticospinal System ◽  
Action Preparation ◽  
Rate Profile

During everyday actions there is a need to be able to withhold movements until the most appropriate time. This motor inhibition is likely to rely on multiple cortical and subcortical areas, but the primary motor cortex (M1) is a critical component of this process. However, the mechanisms behind this inhibition are unclear, particularly the role of the corticospinal system, which is most often associated with driving muscles and movement. To address this, recordings were made from identified corticospinal (PTN, n = 94) and corticomotoneuronal (CM, n = 16) cells from M1 during an instructed delay reach-to-grasp task. The task involved the animals withholding action for ~2 s until a GO cue, after which they were allowed to reach and perform the task for a food reward. Analysis of the firing of cells in M1 during the delay period revealed that, as a population, non-CM PTNs showed significant suppression in their activity during the cue and instructed delay periods, while CM cells instead showed a facilitation during the preparatory delay. Analysis of cell activity during movement also revealed that a substantial minority of PTNs (27%) showed suppressed activity during movement, a response pattern more suited to cells involved in withholding rather than driving movement. These results demonstrate the potential contributions of the M1 corticospinal system to withholding of actions and highlight that suppression of activity in M1 during movement preparation is not evenly distributed across different neural populations. NEW & NOTEWORTHY Recordings were made from identified corticospinal (PTN) and corticomotoneuronal (CM) cells during an instructed delay task. Activity of PTNs as a population was suppressed during the delay, in contrast to CM cells, which were facilitated. A minority of PTNs showed a rate profile that might be expected from inhibitory cells and could suggest that they play an active role in action suppression, most likely through downstream inhibitory circuits.

scholarly journals Cortical and Striatal Electroencephalograms and Apomorphine Effects in the FUS Mouse Model of Amyotrophic Lateral Sclerosis

2021 ◽  
pp. 1-15
Author(s):  
Vasily Vorobyov ◽  
Alexander Deev ◽  
Frank Sengpiel ◽  
Vladimir Nebogatikov ◽  
Aleksey A. Ustyugov
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Neurons ◽  
Cortical Neurons ◽  
Primary Motor Cortex ◽  
Beta Activity ◽  
Systemic Injection ◽  
Eeg Spectra ◽  
Electroencephalogram Eeg ◽  
Lateral Sclerosis

Background: Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of motor neurons resulting in muscle atrophy. In contrast to the lower motor neurons, the role of upper (cortical) neurons in ALS is yet unclear. Maturation of locomotor networks is supported by dopaminergic (DA) projections from substantia nigra to the spinal cord and striatum. Objective: To examine the contribution of DA mediation in the striatum-cortex networks in ALS progression. Methods: We studied electroencephalogram (EEG) from striatal putamen (Pt) and primary motor cortex (M1) in ΔFUS(1–359)-transgenic (Tg) mice, a model of ALS. EEG from M1 and Pt were recorded in freely moving young (2-month-old) and older (5-month-old) Tg and non-transgenic (nTg) mice. EEG spectra were analyzed for 30 min before and for 60 min after systemic injection of a DA mimetic, apomorphine (APO), and saline. Results: In young Tg versus nTg mice, baseline EEG spectra in M1 were comparable, whereas in Pt, beta activity in Tg mice was enhanced. In older Tg versus nTg mice, beta dominated in EEG from both M1 and Pt, whereas theta and delta 2 activities were reduced. In younger Tg versus nTg mice, APO increased theta and decreased beta 2 predominantly in M1. In older mice, APO effects in these frequency bands were inversed and accompanied by enhanced delta 2 and attenuated alpha in Tg versus nTg mice. Conclusion: We suggest that revealed EEG modifications in ΔFUS(1–359)-transgenic mice are associated with early alterations in the striatum-cortex interrelations and DA transmission followed by adaptive intracerebral transformations.

scholarly journals Cerebellar rTMS and PAS effectively induce cerebellar plasticity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Martje G. Pauly ◽  
Annika Steinmeier ◽  
Christina Bolte ◽  
Feline Hamami ◽  
Elinor Tzvi ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Healthy Subjects ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Premotor Cortex ◽  
Motor Pathways ◽  
Non Invasive ◽  
Cerebellar Plasticity

AbstractNon-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative stimulation (PAS), and transcranial direct current stimulation (tDCS) have been applied over the cerebellum to induce plasticity and gain insights into the interaction of the cerebellum with neo-cortical structures including the motor cortex. We compared the effects of 1 Hz rTMS, cTBS, PAS and tDCS given over the cerebellum on motor cortical excitability and interactions between the cerebellum and dorsal premotor cortex / primary motor cortex in two within subject designs in healthy controls. In experiment 1, rTMS, cTBS, PAS, and tDCS were applied over the cerebellum in 20 healthy subjects. In experiment 2, rTMS and PAS were compared to sham conditions in another group of 20 healthy subjects. In experiment 1, PAS reduced cortical excitability determined by motor evoked potentials (MEP) amplitudes, whereas rTMS increased motor thresholds and facilitated dorsal premotor-motor and cerebellum-motor cortex interactions. TDCS and cTBS had no significant effects. In experiment 2, MEP amplitudes increased after rTMS and motor thresholds following PAS. Analysis of all participants who received rTMS and PAS showed that MEP amplitudes were reduced after PAS and increased following rTMS. rTMS also caused facilitation of dorsal premotor-motor cortex and cerebellum-motor cortex interactions. In summary, cerebellar 1 Hz rTMS and PAS can effectively induce plasticity in cerebello-(premotor)-motor pathways provided larger samples are studied.

scholarly journals Effect of opposing needling on motor cortex excitability in healthy participants and in patients with post-stroke hemiplegia: study protocol for a single-blind, randomised controlled trial

Trials ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Mindong Xu ◽  
Yinyu Zi ◽  
Jianlu Wu ◽  
Nenggui Xu ◽  
Liming Lu ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Controlled Trial ◽  
Secondary Outcome ◽  
Post Stroke ◽  
Motor Cortex Excitability ◽  
Opposing Needling ◽  
Single Blind ◽  
Healthy Participants

Abstract Background Opposing needling has an obvious curative effect in the treatment of post-stroke hemiplegia; however, the mechanism of the opposing needling in the treatment of post-stroke hemiplegia is still not clear. The purpose of this study is to investigate the effect of opposing needling on the excitability of primary motor cortex (M1) of healthy participants and patients with post-stroke hemiplegia, which may provide insight into the mechanisms of opposing needling in treating post-stroke hemiplegia. Methods This will be a single-blind, randomised, sham-controlled trial in which 80 healthy participants and 40 patients with post-stroke hemiplegia will be recruited. Healthy participants will be randomised 1:1:1:1 to the 2-Hz, 50-Hz, 100-Hz, and sham electroacupuncture groups. Patients with post-stroke hemiplegia will be randomised 1:1 to the opposing needling or conventional treatment groups. The M1 will be located in all groups by using neuroimaging-based navigation. The stimulator coil of transcranial magnetic stimulation (TMS) will be moved over the left and right M1 in order to identify the TMS hotspot, followed by a recording of resting motor thresholds (RMTs) and motor-evoked potentials (MEPs) of the thenar muscles induced by TMS before and after the intervention. The primary outcome measure will be the percent change in the RMTs of the thenar muscles at baseline and after the intervention. The secondary outcome measures will be the amplitude (μV) and latency (ms) of the MEPs of the thenar muscles at baseline and after the intervention. Discussion The aim of this trial is to explore the effect of opposing needling on the excitability of M1 of healthy participants and patients with post-stroke hemiplegia. Trial registration Chinese Clinical Trial Registry ChiCTR1900028138. Registered on 13 December 2019.

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