scholarly journals Are ipsilateral motor evoked potentials subject to intracortical inhibition?

2016 ◽  
Vol 115 (3) ◽  
pp. 1735-1739
Author(s):  
Alana B. McCambridge ◽  
James W. Stinear ◽  
Winston D. Byblow
Keyword(s):  
Evoked Potentials ◽  
Primary Motor Cortex ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Conditioning Stimulus ◽  
Elbow Flexion ◽  
Intracortical Inhibition ◽  
Motor Tasks ◽  
Active Motor

Paired-pulse transcranial magnetic stimulation (TMS) can be used to examine intracortical inhibition in primary motor cortex (M1), termed short-interval intracortical inhibition (SICI). To our knowledge, SICI has only been demonstrated in contralateral motor evoked potentials (MEPs). Ipsilateral MEPs (iMEPs) are assumed to reflect excitability of an uncrossed oligosynaptic pathway, and can sometimes be evoked in proximal upper-limb muscles using high-intensity TMS. We examined whether iMEPs in the biceps brachii (BB) would be suppressed by subthreshold conditioning, therefore demonstrating SICI of iMEPs. TMS was delivered to the dominant M1 to evoke conditioned (C) and nonconditioned (NC) iMEPs in the nondominant BB of healthy participants during weak bilateral elbow flexion. The conditioning stimulus intensities tested were 85%, 100%, and 115% of active motor threshold (AMT), at 2 ms and 4 ms interstimulus intervals (ISI). The iMEP ratio (C/NC) was calculated for each condition to assess the amount of inhibition. Inhibition of iMEPs was present at 2 ms ISI with 100% and 115% AMT (both P < 0.03), mediated by a reduction in persistence and size (all P < 0.05). To our knowledge, this is the first demonstration of SICI of iMEPs. This technique may be useful as a tool to better understand the role of ipsilateral M1 during functional motor tasks.

scholarly journals The Excitability of Ipsilateral Motor Evoked Potentials Is Not Task-specific and Spatially Distinct From the Contralateral Motor Hotspot

2022 ◽  
Author(s):  
Nelly Seusing ◽  
Sebastian Strauss ◽  
Robert Fleischmann ◽  
Christina Nafz ◽  
Sergiu Groppa ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Evoked Potentials ◽  
Primary Motor Cortex ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Elbow Flexion ◽  
Motor Pathways ◽  
Task Dependence ◽  
Flexion Extension ◽  
Voluntary Contractions

Abstract ObjectiveThe role of ipsilateral descending motor pathways in voluntary movement of humans is still a matter of debate. Few studies have examined the task dependent modulation of ipsilateral motor evoked potentials (iMEPs). Here, we determined the location of upper limb biceps brachii (BB) representation within the ipsilateral primary motor cortex. MethodsMR-navigated transcranial magnetic stimulation mapping of the dominant hemisphere was undertaken with twenty healthy participants who made tonic unilateral, bilateral homologous or bilateral antagonistic elbow flexion-extension voluntary contractions. Map center of gravity (CoG) and area for each BB were obtained. ResultsThe map CoG of the ipsilateral BB was located more anterior-laterally than those of the contralateral BB within the primary motor cortex. However different tasks had no effect on either the iMEP CoG location or the size. ConclusionOur data suggests that ipsilateral and contralateral MEP might originate in distinct adjacent neural populations in the primary motor cortex, independent of task dependence.

Influence of Short-Interval Intracortical Inhibition on Short-Interval Intracortical Facilitation in Human Primary Motor Cortex

2010 ◽  
Vol 104 (3) ◽  
pp. 1382-1391 ◽  
Author(s):  
Yuichiro Shirota ◽  
Masashi Hamada ◽  
Yasuo Terao ◽  
Hideyuki Matsumoto ◽  
Shinya Ohminami ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Short Interval ◽  
Conditioning Stimulus ◽  
Intracortical Inhibition ◽  
Intracortical Facilitation ◽  
Paired Pulse ◽  
Active Motor ◽  
Second Peak ◽  
Pulse Stimulation

Using the paired-pulse paradigm, transcranial magnetic stimulation (TMS) has revealed much about the human primary motor cortex (M1). A preceding subthreshold conditioning stimulus (CS) inhibits the excitability of the motor cortex, which is named short-interval intracortical inhibition (SICI). In contrast, facilitation is observed when the first pulse (S1) is followed by a second one at threshold (S2), named short-interval intracortical facilitation (SICF). SICI and SICF have been considered to be mediated by different neural circuits within M1, but more recent studies reported relations between them. In this study, we performed triple-pulse stimulation consisting of CS-S1-S2 to further explore putative interactions between these two effects. Three intensities of CS (80–120% of active motor threshold: AMT) and two intensities of S2 (120 and 140% AMT) were combined. The SICF in the paired-pulse paradigm exhibited clear facilitatory peaks at ISIs of 1.5 and 3 ms. The second peak at 3 ms was significantly suppressed by triple-pulse stimulation using 120% AMT CS, although the first peak was almost unaffected. Our present results obtained using triple-pulse stimulation suggest that each peak of SICF is differently modulated by different intensities of CS. The suppression of the second peak might be ascribed to the findings in the paired-pulse paradigm that CS mediates SICI by inhibiting later I waves such as I3 waves and that the second peak of SICF is most probably related to I3 waves. We propose that CS might inhibit the second peak of SICF at the interneurons responsible for I3 waves.

Intracortical Inhibition During Volitional Inhibition of Prepared Action

2006 ◽  
Vol 95 (6) ◽  
pp. 3371-3383 ◽  
Author(s):  
James P. Coxon ◽  
Cathy M. Stinear ◽  
Winston D. Byblow
Keyword(s):  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Corticomotor Excitability ◽  
Hand Muscles ◽  
Cortical Level ◽  
A Site ◽  
Intrinsic Hand Muscles ◽  
Inhibitory Networks

Volitional inhibition is the voluntary prevention of a prepared movement. Here we ask whether primary motor cortex (M1) is a site of convergence of cortical activity associated with movement preparation and volitional inhibition. Volitional inhibition was studied by presenting a stop signal before execution of an anticipated response that requires a key lift to intercept a revolving dial. Motor evoked potentials (MEPs) were elicited in intrinsic hand muscles by transcranial magnetic stimulation (TMS) to assess corticomotor excitability and short interval intracortical inhibition (sICI) during task performance. The closer the stop cue was presented to the anticipated response, the harder it was for subjects to inhibit their response. Corticomotor pathway excitability was temporally modulated during volitional inhibition. Using subthreshold TMS, corticomotor excitability was reduced for Stop trials relative to Go trials from 140 ms after the cue. sICI was significantly greater for Stop trials compared with Go trials at a time that preceded the onset of muscle activity associated with the anticipated response. These results provide evidence that volitional inhibition is exerted at a cortical level and that inhibitory networks within M1 contribute to volitional inhibition of prepared action.

Event-related desynchronization reflects downregulation of intracortical inhibition in human primary motor cortex

2013 ◽  
Vol 110 (5) ◽  
pp. 1158-1166 ◽  
Author(s):  
Mitsuaki Takemi ◽  
Yoshihisa Masakado ◽  
Meigen Liu ◽  
Junichi Ushiba
Keyword(s):  
Motor Cortex ◽  
Motor Imagery ◽  
Sensorimotor Cortex ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Hand Movement ◽  
Intracortical Inhibition ◽  
Imagery Task ◽  
Event Related Desynchronization

There is increasing interest in electroencephalogram (EEG)-based brain-computer interface (BCI) as a tool for rehabilitation of upper limb motor functions in hemiplegic stroke patients. This type of BCI often exploits mu and beta oscillations in EEG recorded over the sensorimotor areas, and their event-related desynchronization (ERD) following motor imagery is believed to represent increased sensorimotor cortex excitability. However, it remains unclear whether the sensorimotor cortex excitability is actually correlated with ERD. Thus we assessed the association of ERD with primary motor cortex (M1) excitability during motor imagery of right wrist movement. M1 excitability was tested by motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) with transcranial magnetic stimulation (TMS). Twenty healthy participants were recruited. The participants performed 7 s of rest followed by 5 s of motor imagery and received online visual feedback of the ERD magnitude of the contralateral hand M1 while performing the motor imagery task. TMS was applied to the right hand M1 when ERD exceeded predetermined thresholds during motor imagery. MEP amplitudes, SICI, and ICF were recorded from the agonist muscle of the imagined hand movement. Results showed that the large ERD during wrist motor imagery was associated with significantly increased MEP amplitudes and reduced SICI but no significant changes in ICF. Thus ERD magnitude during wrist motor imagery represents M1 excitability. This study provides electrophysiological evidence that a motor imagery task involving ERD may induce changes in corticospinal excitability similar to changes accompanying actual movements.

scholarly journals Writing's Shadow: Corticospinal Activation during Letter Observation

2012 ◽  
Vol 24 (5) ◽  
pp. 1138-1148 ◽  
Author(s):  
Masahiro Nakatsuka ◽  
Mohamed Nasreldin Thabit ◽  
Satoko Koganemaru ◽  
Ippei Nojima ◽  
Hidenao Fukuyama ◽  
...  
Keyword(s):  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Single Pulse ◽  
Random Order ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Motor Memory ◽  
F Wave ◽  
The Right

We can recognize handwritten letters despite the variability among writers. One possible strategy is exploiting the motor memory of orthography. By using TMS, we clarified the excitatory and inhibitory neural circuits of the motor corticospinal pathway that might be activated during the observation of handwritten letters. During experiments, participants looked at the handwritten or printed single letter that appeared in a random order. The excitability of the left and right primary motor cortex (M1) was evaluated by motor-evoked potentials elicited by single-pulse TMS. Short interval intracortical inhibition (SICI) of the left M1 was evaluated using paired-pulse TMS. F waves were measured for the right ulnar nerve. We found significant reduction of corticospinal excitability only for the right hand at 300–400 msec after each letter presentation without significant changes in SICI. This suppression is likely to be of supraspinal origin, because of no significant alteration in F-wave amplitudes. These findings suggest that the recognition of handwritten letters may include the implicit knowledge of “writing” in M1. The M1 activation associated with that process, which has been shown in previous neuroimaging studies, is likely to reflect the active suppression of the corticospinal excitability.

Corticomotor plasticity and learning of a ballistic thumb training task are diminished in older adults

2009 ◽  
Vol 107 (6) ◽  
pp. 1874-1883 ◽  
Author(s):  
Nigel C. Rogasch ◽  
Tamara J. Dartnall ◽  
John Cirillo ◽  
Michael A. Nordstrom ◽  
John G. Semmler
Keyword(s):  
Older Adults ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Training Task ◽  
Abductor Pollicis Brevis ◽  
Corticomotor Excitability ◽  
Old Adults ◽  
Young Subjects

This study examined changes in corticomotor excitability and plasticity after a thumb abduction training task in young and old adults. Electromyographic (EMG) recordings were obtained from right abductor pollicis brevis (APB, target muscle) and abductor digiti minimi (ADM, control muscle) in 14 young (18–24 yr) and 14 old (61–82 yr) adults. The training task consisted of 300 ballistic abductions of the right thumb to maximize peak thumb abduction acceleration (TAAcc). Transcranial magnetic stimulation (TMS) of the left primary motor cortex was used to assess changes in APB and ADM motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) before, immediately after, and 30 min after training. No differences in corticomotor excitability (resting and active TMS thresholds, MEP input-output curves) or SICI were observed in young and old adults before training. Motor training resulted in improvements in peak TAAcc in young (177% improvement, P < 0.001) and old (124%, P = 0.005) subjects, with greater improvements in young subjects ( P = 0.002). Different thumb kinematics were observed during task performance, with increases in APB EMG related to improvements in peak TAAcc in young ( r2 = 0.46, P = 0.008) but not old ( r2 = 0.09, P = 0.3) adults. After training, APB MEPs were 50% larger ( P < 0.001 compared with before) in young subjects, with no change after training in old subjects ( P = 0.49), suggesting reduced use-dependent corticomotor plasticity with advancing age. These changes were specific to APB, because no training-related change in MEP amplitude was observed in ADM. No significant association was observed between change in APB MEP and improvement in TAAcc with training in individual young and old subjects. SICI remained unchanged after training in both groups, suggesting that it was not responsible for the diminished use-dependent corticomotor plasticity for this task in older adults.

scholarly journals Corticospinal excitability to the biceps and triceps brachii during forward and backward arm cycling is direction- and phase-dependent

2020 ◽  
Vol 45 (1) ◽  
pp. 72-80
Author(s):  
Anna. P. Nippard ◽  
Evan. J. Lockyer ◽  
Duane. C. Button ◽  
Kevin. E. Power
Keyword(s):  
Evoked Potentials ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Elbow Flexion ◽  
Corticospinal Excitability ◽  
Extension Phase ◽  
Triceps Brachii ◽  
Arm Cycling ◽  
Spinal Excitability ◽  
Flexion And Extension

The purpose of this study was to evaluate corticospinal excitability to the biceps and triceps brachii during forward (FWD) and backward (BWD) arm cycling. Corticospinal and spinal excitability were assessed using transcranial magnetic stimulation and transmastoid electrical stimulation to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials (CMEPs), respectively. MEPs and CMEPs were recorded from the biceps and triceps brachii during FWD and BWD arm cycling at 2 positions, 6 and 12 o’clock. The 6 o’clock position corresponded to mid-elbow flexion and extension during FWD and BWD cycling, respectively, while 12 o’clock corresponded to mid-elbow extension and flexion during FWD and BWD cycling, respectively. During the flexion phase, MEP and CMEP amplitudes of the biceps brachii were higher during FWD cycling. However, during the extension phase, MEP and CMEP amplitudes were higher during BWD cycling. For the triceps brachii, MEP amplitudes were higher during FWD cycling regardless of phase. However, CMEP amplitudes were phase-dependent. During the flexion phase, CMEPs of the triceps brachii were higher during FWD cycling compared with BWD, but during the extension phase CMEPs were higher during BWD cycling compared with FWD. The data suggest that corticospinal and spinal excitability to the biceps brachii is phase- and direction-dependent. In the triceps brachii, spinal, but not corticospinal, excitability is phase-dependent when comparing FWD and BWD cycling. Novelty This is the first study to assess corticospinal excitability during FWD and BWD locomotor output. Corticospinal excitability during arm cycling depends on the direction, phase, and muscle being assessed.

scholarly journals Distributed cortical structural properties contribute to motor cortical excitability and inhibition

2017 ◽  
Author(s):  
Eran Dayan ◽  
Virginia López-Alonso ◽  
Sook-Lei Liew ◽  
Leonardo G. Cohen
Keyword(s):  
Motor Cortex ◽  
Structural Properties ◽  
Motor Function ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Support Vector

AbstractThe link between the local structure of the primary motor cortex and motor function has been well documented. However, motor function relies on a network of interconnected brain regions and the link between the structural properties characterizing these distributed brain networks and motor function remains poorly understood. Here, we examined whether distributed patterns of brain structure, extending beyond the primary motor cortex can help classify two forms of motor function: corticospinal excitability and intracortical inhibition. To this effect, we recorded high-resolution structural magnetic resonance imaging scans in 25 healthy volunteers. To measure corticospinal excitability and inhibition in the same volunteers we recorded motor evoked potentials (MEPs) elicited by single-pulse transcranial magnetic stimulation (TMS) and short-interval intracortical inhibition (SICI) in a separate session. Support vector machine (SVM) pattern classification was used to identify distributed multivoxel gray matter areas, which distinguished subjects who had lower and higher MEPs and SICIs. We found that MEP and SICI classification could be predicted based on a widely distributed, largely non-overlapping pattern of voxels in the frontal, parietal, temporal, occipital and cerebellar regions. Thus, structural properties distributed over the brain beyond the primary motor cortex relate to motor function.

Corticospinal excitability of the biceps brachii is higher during arm cycling than an intensity-matched tonic contraction

2014 ◽  
Vol 112 (5) ◽  
pp. 1142-1151 ◽  
Author(s):  
Davis Forman ◽  
Amita Raj ◽  
Duane C. Button ◽  
Kevin E. Power
Keyword(s):  
Evoked Potentials ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Maximum Amplitude ◽  
Elbow Flexion ◽  
Tonic Contraction ◽  
Corticospinal Excitability ◽  
Spinal Motoneuron ◽  
Motoneuron Excitability ◽  
Arm Cycling

Human studies have not assessed corticospinal excitability of an upper-limb prime mover during arm cycling. The purpose of the present study was to determine whether supraspinal and/or spinal motoneuron excitability of the biceps brachii was different between arm cycling and an intensity-matched tonic contraction. We hypothesized that spinal motoneuron excitability would be higher during arm cycling than an intensity-matched tonic contraction. Supraspinal and spinal motoneuron excitability were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract, respectively. TMS-induced motor-evoked potentials (MEPs) and TMES-induced cervicomedullary-evoked potentials (CMEPs) were assessed at three separate positions (3, 6, and 12 o'clock relative to a clock face) during arm cycling and an intensity-matched tonic contraction. MEP amplitudes were 7.2 and 8.8% maximum amplitude of the compound muscle action potential (Mmax) larger during arm cycling compared with a tonic contraction at the 3 ( P < 0.001) and 6 o'clock ( P < 0.001) positions, respectively. There was no difference between tasks during elbow extension (12 o'clock). CMEP amplitudes were 5.2% Mmax larger during arm cycling compared with a tonic contraction at the 3 o'clock position ( P < 0.001) with no differences seen at midflexion (6 o'clock) or extension (12 o'clock). The data indicate an increase in the excitability of corticospinal neurons, which ultimately project to biceps brachii during the elbow flexion portion of arm cycling, and increased spinal motoneuron excitability at the onset of elbow flexion during arm cycling. We conclude that supraspinal and spinal motoneuron excitability are phase- and task-dependent.

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